DIY 16MB 30-Pin FPM SIMMs: Supercharge Your Vintage Hardware!

This is a follow-up of my 4MB SIMM project. At that time, I created an altered version of SIMM PCBs that integrated a mod to operate EDO memory chips in FPM. A simple switch toggled between both modes and allowed me to get my 386 board to 32MB of system memory. Today, we are pushing the board to the limit! I will attempt to create 16MB SIMMs - the maximum supported capacity of 30-pin SIMMs. Let's see if I will be successful to get my 386 to 64 or even 128MB!
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▬▬▬▬ Timestamps ▬▬▬▬▬▬▬▬▬▬▬▬▬▬
00:00 Intro
01:36 Recap
04:43 Maximum capacity
05:31 Research
08:34 Preparation
09:45 Design PCBs
10:57 Unpacking
11:51 Building SIMMs
16:50 Final touches
17:19 Test
19:29 Where to get?

[@bitsundbolts]

Hi there! I hope you like the 30-pin SIMM 16MB memory module. Would you be interested to get a set of 2, 4, or even 8 modules? I want to understand what the demand is for such modules. Hit the like button of this comment and reply with how many modules you would be interested in. This is not an order, I just want to know if I should make a few and utilize the memory modules you have seen in this video! Thanks everyone for watching, commenting, and liking! Cheers

[@AttilaSVK]

This is awesome. I could use 8 such modules for my Macintosh SE/30 to max out the memory :) Btw, the Sound Blaster AWE32 also supports 16MB SIMMs, but the usable memory is limited to 28MB due to the 4MB ROM sharing the address space with the RAM.

[@MarcoGPUtuber]

I know how to get chips for these so you don't have to desolder them from DIMMs.

[@harvaldi]

@@AttilaSVK I would love to have 2 for my Sound Blaster AWE32! :D

[@philpem]

I'd be interested in a set of four - I'm curious if my 386 boards can go as far as yours!

[@BadManiac]

I'd absolutely be interested in a set of 4. Being able to switch between FPM and EDO would be invaluable for testing old hardware. Also can I please come visit your scrapyard one day? That place looks like heaven! :)

[@Robin96]

The 64 MB RAM count was so funny i watched it several times. I really like the ram counting sound on old computers

[@jammi__]

The counting algorithm was also the same, but CPU performance grew, so on a 286, it'd slowly count up to 1MB with a tick...tick...tick, a fast 486 does its 32MB in a "brrrrrrrrrrp" in a few seconds, and some late Athlon counts 2GB in a brief high-pitched "zeet". I guess if contemporary ones still did the same, it'd just be in the ultrasound spectrum and thus inaudible to mere humans.

[@Armand79th]

I've got 64GB in my main rig and I don't even see a RAM count. 😅

[@Spyd77]

I had a 8088 computer for way to long. I was young and had no money, so I saved all the money I got to upgrade my XT. The day I got enough, I bought a motherboard with an Intel 386SX, and 1Mb memory. The motherboard had 4 SIMM slots, and I wanted a single 1Mb module, but on the store they told me that I had to fill at least a bank (2 modules). My options were 4x256Kb, or 2x1Mb. No 512Kb modules. Having waited more than a year to be able to update my computer, I caved and got 4x256Kb, my options to upgrade gone. Then I had a 386sx (I think 25Mhz, don't remember), 1Mb of RAM, an Hercules graphics card, a green-phosphor monitor, a single 5,25" 360Kb floppy disk, and an MFM 20Mb hard disk. It wasn't much, but Windows 3.1 worked well and the CGA software emulation worked SOOOO much better.

[@2dfx]

When you started up that 386 for the first time with 64MB I had a huge smile on my face as I'm sure you did. What a really great achievement and just shows you that "official" and "supported" specifications may be two different things! Thanks for sharing.

[@bitsundbolts]

I am working on an updated version that hopefully follows the specifications on the datasheet. I do it mostly to learn more. The current modules seem to work well and I got plenty of comments supporting both perspectives. There will be a follow up on this one very soon!

[@n.stephan9848]

8:55 That scrapyard is magnificent, I wish I had a place like that nearby with even a quarter of the stuff portrayed there.

[@0xTJ]

I love how cheap and fast PCB production has made creating custom modules like this, especially for non-standard things like the EDO->FPM adapter.

[@bitsundbolts]

It is really easy! And the learning curve to my first PCB wasn't as steep as it might seem.

[@billybbob18]

In 2000, our home PC only had 32MB RAM, 3GB HHD and 300MHZ AMD K6-2 processor (586?). The fact you were able to get twice the ram on a system at least two generations older is impressive.

[@zaxmaxlax]

We had a k6 too, classic. I still have the chip as a memento. I also remember my cousin had a 486 amd I think, the motherboard had the option of 30pin or 72pin, if I'm not mistaken, because I definetly remember those 30pin RAM sticks and I always found them slick and clean compared to the bigger ones.

[@TheRaker1000]

your PCBWay ads are the only ads on YT that i actually watch. not even just letting the ad roll while i do other stuff, you have me paying attention and engrossed in the product. can we please make all advertising like this? relevant, informative, confident.

[@bitsundbolts]

Oh well, thank you 😊. I usually get the opposite view about ads in general. But without PCBWay, I wouldn't be able to do all this. Not only do I get access to their services and products, but they also help a lot with their financial support. It wouldn't be feasible without sponsorships to run a channel like this. Thanks for your support! 🙏

[@UpLateGeek]

Congratulations on such a successful project! Now people can finally stop bugging me to make 16MB SIMMs! Of course I'm kidding, I only got a few messages asking about them since I published that project so many years ago. But I'm glad someone finally took up the mantle and did what I never got around to doing. I had every intention of getting back to this project and making my own 16MB modules, at one point even tracking down a source for the requisite chips, but they were very expensive since they were NOS, so I never got around to ordering them. And then my career took the front seat and I've had neither the spare time or energy for such a project since then. But this is an even better design, since it's using chips that are basically scrap. The fact that you can use EDO chips really opens the door to potentially using other chips with a relatively simple modification to the design. So congratulations once again, you've really done some impressive work!

[@bitsundbolts]

Thank you so much! Without you paving the way, I would have never picked up on PCB design. Your Gerber files and schematics allowed me to learn about those modules. Thank you for your work!

[@conundrum2007]

@@bitsundbolts Someone should make a 64GB DDR4 SODIMM now, purely for the heck of it.

[@colinmoller4321]

Oh man, I have to agree, the black PCBs give it a really badass look!

[@bitsundbolts]

It makes those modules look more premium. I'm looking forward to making these in larger quantities 😅

[@tomasz89g]

I was happy with 5MB back in the day. 64MB is INSANE for a 386, nice job, pushing it to double the stated maximum!

[@bitsundbolts]

I agree - 64MB is not really useful for a 386. Most of the memory is not usable by the software that runs on such a platform. As you said, the driver behind this project was to see what is possible. I learned a lot by going through the documentation and make sense of it. And finally also to understand, why we can only use those high capacity modules in memory bank 0.

[@tomasz89g]

@@bitsundbolts RAMDisk would be very useful. Large smartdrv cache. But back in the day, this kind of system would have fetched a very high price. You are right, RAM was expensive!

[@OpenGL4ever]

@@bitsundbolts 64 MiB might be usable for compiling source code. You could benchmark it with 8, 16, 32 and 64 MiB to see if there is a difference.

[@acubley]

@@bitsundbolts Back in the day I was super happy when I got my P90 system to 8mb. I put 4mb to a ram drive and had the autoexec.bat copy my current game there. 64mb would have been heaven. 😵

[@locallemonadestand8130]

The OG Xbox has that much memory gawd damn

[@philpem]

Nice work! I never thought I'd see a 386 with 64MB RAM. I always thought they topped out at 16. This absolutely blew my mind!

[@bitsundbolts]

386SX systems seem to have this limitation of 16 MBs. Glad to hear that you have seen something new in this video! 🙂

[@hatbabe]

@@bitsundbolts Yeah that's one part of the 'cutdown' part of a low-price 386 alternative to what then got called the 386DX, only a 24-bit address bus was exposed on the 386SX. Internally the CPU could act like it had a full 32 bits of address space but physically impossible to talk directly to more than 16MB. As was invariably the case from SIPP to SIMM to DIMM to SODIMM, machines may be designed to take a bigger stick capacity, but 2x the RAM would cost so much more than double the cost of the smaller sticks. They were at first only for hardcore uses, then as the line aged they became a bit more affordable, and then technology had moved on to another speed/bus/etc arrangement so they never became commodity parts because the next high and mid range systems used the commodity new thing instead.

[@TheUAoB]

​@@bitsundboltsThat's to be expected since the 386sx shares the 24bit address bus of the 286. Only "real" 386s have the 32bit address bus

[@BeniD82]

Years ago I ordered a number of 128MB 5v EDO DIMMs and the supplier shipped 3.3v modules instead. When I told them about the mistake they told me they'll send the correct replacement and to just keep the 3.3v sticks. Never had any use for them until now it seems. My chips are Micron parts but they appear to be 16Mx4 as well and are sharing the same pinout. Guess I should sacrifice a stick out of my pile to create a slew of 16MB 30pin SIMMs. It's a parity module too so two additional chips for an extra 30pin module... Awesome job!

[@bitsundbolts]

Oh, wow. I always have to send stuff back 😅. Good for you - I guess you found a use case for those modules now! I wonder what you possibly could have used those EDO modules for otherwise (I guess you have the 168-pin version). I would rather use SD-Ram since it is probably a lot faster.

[@argoneum]

Back in 1990s I had a borrowed Am386DX-40 machine with 4MB of RAM (and without FPU). It run Win3.11 For Workgroups on MS-DOS 6.22. There was Corel 5 and Corel 7 installed. Corel 5 was working fine, Corel 7 had trouble fitting in RAM and was swapping a lot. It was fun seeing Corel Draw 5 actually drawing the business cards when a file was opened.

[@bitsundbolts]

Oh, I remember Corel. I think I had version 4. That was for Windows 3.1 if I'm not mistaken. It was slow if I remember correctly. Those vector graphics just took some time to be drawn on screen.

[@MarcoGPUtuber]

0:36 I found a 16-SIMM board in the scrapyard and a friend gave me another one. Very happy to own these.

[@bitsundbolts]

They are no longer that common. I have many and not really any use for them. I prefer larger capacities. However, if you want to build a period correct system, those 1MB modules are probably the sweet spot.

[@MarcoGPUtuber]

@@bitsundbolts I had never even seen one and wasn't aware they existed, I was going to make it one of my retro machines and max it out with what I could find. Once I fix the board though.

[@pgtmr2713]

​@@bitsundbolts It's weird to see "period correct." I'd say who cares. But the there's automotive, where original, oem, has the most value. There it makes sense since most can't build better than the manufacturer, and no one wants to buy junk used. I think we had 1mb in our 386 back in 92

[@xephorce]

I love this. saving chips that might have gone unused for the rest of time. this is something that needs to be done more often.

[@bitsundbolts]

Haha, I am working hard on hopefully more projects like this in the future!

[@Arti9m]

Please note that there have been reports on similar chips dying in 5V systems. On the other hand, I have a few SIMM72 5V modules made with 3.3V-only chips but indended for 5V boards. They don't even have the regulators, just two diodes in series to drop the voltage to 3.5-ish. Also there's another way of making 16M SIMM30 sticks. It involves 8 4x4 chips and a PAL chip for reorganizing the memory. Works kinda like SimmConn. I do have the PCBs drawn and firmware written for PAL but just don't have the time to build it 😢 Great video as usual!

[@bitsundbolts]

Hey! Good to hear from you again! Thanks for pointing out the issue with the 5v issue. I'm going to research the topic and try to address the issue somehow. I have seen other SIMMs that also just have the voltage regulator and a few capacitors. I'm confused to be honest. But I'm researching level shifters at the moment.

[@vitobelflores6510]

Deja tu mujer y tendrás tiempo de sobra. Estos proyectos sí venden si los nostálgicos sabemos que existen.

[@Edmilho]

Excellent work! Congratulations on the video and success to the channel.

[@ileox4170]

Well Done ❤! I don‘t have any clue about FPM or EDO Memory at all but the explination is on point and the execution as well :D

[@stoojinator]

This is freaking awesome! What an awesome project!

[@bitsundbolts]

Thank you 😊

[@chrisrudi7162]

The project is very nice 👍 Really great, especially since it is very difficult to get really large modules. I also have a 386DX 40 MHz with 64 MB, but I bought these modules ready-made many years ago.

[@christianhansen3590]

The audible sighs made me chuckle 😊 But a really cool project!

[@LellePrinter82]

Impressive, great work. Impressive what u can salvage from old computer parts. That scrapyard looks like paradise to me, i've would've spent hours there. I have loved electronics since I was a young kid, it started when my dad bought his first pc with a 12mhz 286 cpu. Always been fascinated by computers and stereo equipment. I'm both into retro pc and retro stereo components, and I always will be. In highschool my teachers told me that I knew more about pc's than them, they were fascinated by my electronics/pc knowledge.

[@christ2290]

Man, you are LEGIT. Great work!

[@bitsundbolts]

Thank you 👍😊

[@jamesrdgrs]

Another awesome video and another win for making this hobby a little more affordable! Thank you!!!!

[@bitsundbolts]

Absolutely! It looks like I will have to make quite a few of those modules soon!

[@blakecasimir]

Fantastic work as always.

[@bitsundbolts]

Thank you!

[@Ale.K7]

Amazing!! :D That Cyrix FasMath FPU is gorgeous. I also find those COB SIMMs you showed at the start of the video pretty interesting! It's been a long time since I last played with my 386s, but I remember 4MB being the most I could use... So I think i don't have any module larger than 1MB (and there's also the possibility that I achieved said 4 megabytes on a board with 8 sockets and 512KB per module being my maximum!).

[@bitsundbolts]

Most of my SIMMs are 1MB modules except for the ones I made myself. I think there must also be a few 256kb ones.

[@r4z4m4t4z]

nice vid, great work! 30 pin ram, so long ago, my 386 sx 33 struggling to get it going when adding more ram, so fun.

[@bitsundbolts]

If I am not mistaken, a 386SX cannot support more than 16MB.

[@PhG1961]

What an awesome video and a great id!

[@Ajdin87]

Amazing. Thank you for everything you do.

[@sebastian19745]

I once got a set (4 pieces) of 4M 30-pin RAM modules. Man, I was so happy, I used them on my 486 with 2x16M FPM 72-pin RAM modules. Win 95 was very happy with that extra memory but, thinking now, it must have been quite slow because of the 30-pin/72 pin mix. However, I had 256k, 512k, 1M, 4M and I have seen 2M 30-pin RAM sticks but 16M is a first. Congratulations!

[@bingusbongus9807]

16 MB is so cool, thats why i love the ez80, awesome 24 bit adress space

[@Choralone422]

Excellent work! It would have been incredible (and expensive!) to have that amount of memory in a 386 system back in those days!

[@bitsundbolts]

Oh absolutely!

[@ChrisR3tro]

Loved that bit about the meaning of SLC in the Opti chipset model name 😂

[@mesterak]

This was simply amazing work!

[@bitsundbolts]

Thank you very much!

[@Soso-km8er]

Epic and inspiring. This could actually be a business for old Samplers where RAM got super expensive. An E-MU E IV is much more fun with 128 MB.

[@BarsMonster]

Great job! I think I can finally make myself some - I've got a box of old DIMMs that I can now put to good use :-)

[@bitsundbolts]

I wonder how many of those SD-like modules with EDO memory chips exist. I have never seen them before. Just once, when I visited the scrapyard, I found all those modules and was like 'eh, let's take them. Maybe they will be useful in the future'... And here we go! I hope you can make good use of the PCBs!

[@oldconsolegaming]

Thanks so much I had a ton of sim modules that where from a different pc that did not physically fit in my 486 pc now I can use them (I believe they where server or smth else) and now I can put them to use without throwing them out!

[@bitsundbolts]

I'm working on an updated version of the PCBs. They should better support 3.3 volt memory chips.

[@Popclone]

Watching your retro upgrades is like watching NASA upgrade Voyager 1. Keep it up.

[@bitsundbolts]

Haha, thanks for comparing my upgrades to Voyager 1 😅 - quite an honor! I'll try my best to keep the content interesting

[@pavelmityagin8655]

Fantastic!!!! Amazing!!!! Great job, thank you!!!

[@br0wnd]

If I could go back in time and show one video to myself as a teenager, it'd be this one. I know I would have been in complete awe seeing this much ram on a 386!

[@lesar23]

What a LEGEND you are.

[@rallyscoot]

saved the world

[@Alchemetica]

I stumbled upon this video, and it brought back a lot of memories. I no longer have my XT, 286, think I might have a 386. Definitely have 486, Pentium, Pentium II and a number of modern computers up to 2023. Just can't bring myself to taking them to a recycle centre. I like your video, an offbeat project , but most interesting. Thanks. Best wishes from Australia.

[@bitsundbolts]

Thank you! I'm happy to hear that this video brought back a lot of memories!

[@stultorum_caelum]

This is a great video. I have an old soyo 486 motherboard. It has 8 30pin simm slots and sis chipset. A long time ago, I saw in the manual that it could be installed up to 128MB, so I knew that. At the time, 16M modules were very expensive and uncommon, so I never had a chance to try them. Recently I was able to get four 16M modules for cheap. So I tried installing these and they didn't work properly. I look forward to seeing you work on 486 motherboards as well.

[@mo0seboy]

I had a 486 DX2-66 machine with a weird motherboard that had 3 72 pin SIMM slots. I ended up populating it with 3x16MB modules for a total of 48MB of capacity. It was a fun machine to put slackware linux on.

[@pongisan3658]

Holy crap this is so cool!

[@retropcscotland4645]

I loved Soyo back in the day. I used those branded boards all the way up to socket 478. They recently started up again in China.

[@loveller]

Your skills will be in high demand right before Y3k. Keep up the great work.

[@hobbified]

From what I can remember I never actually had a 386 back in the day - I went from a 286 Tandy to a 486DX2-66 with 16MB.

[@zytechnology]

I used to solder leg onto mine to use them as SIPP modules :) Much fun ! !... people were nicer during that time...

[@K10driver]

When the 386 counted up to 64MB the first time, I had to laugh like you did. Insane idea and great implementation! Another question: I am an earlytime member and from all the videos I have watched I might think you are German. There are some hidden words and things you did that make me think that. Am I wrong?

[@bitsundbolts]

Yes, I am German - you are right. Listening to the memory test counting up is just great and I am glad those PCBs worked! Although, after making the 4MB SIMMs, it wasn't as challenging anymore.

[@K10driver]

@@bitsundbolts Dann hab ich doch richtig gehört. Ich glaube es war in einem der P2B Videos wo Du ganz kurz auf deutsch geflucht hast.

[@tezinho81]

I use a SIMM from my very own first 486 pc (1995 iirc) as a keyfob. It's a link to my past that I carry every day.

[@UXXV]

This is like voodoo to me! Love it

[@volkhen0]

Thanks for your effort!

[@bitsundbolts]

My pleasure!

[@viktorgorbunov]

I've remember how I switched from 1M ( 47$ for student was a good money ) to 4M, it was amazing.

[@HBAVHS]

Perfekt. Dann werd ich gleich mal Platinen bestellen. Dank dir. Hammergeil!

[@bitsundbolts]

Haha, kein Problem! Viel Spaß damit!

[@ukmk3supra]

I'm just constantly in awe of these scrap yards - nothing like this in the UK :(

[@bitsundbolts]

Ah, I am really fortunate to have access to one in my area and regulations are almost nonexistent! Paradise for scrap hunters 😊

[@Darkstar2342]

@@bitsundbolts what country is that scrap yard in? I'm guessing central europe somewhere (because some of the modules in your video had German labels on them) but here it's almost impossible to get access to a scrap yard as mere mortal...

[@RetroShare2]

@@bitsundbolts where is that scrapeyard?

[@evandrochaves9596]

UAE, not in europe

[@bitsundbolts]

I live in the United Arab Emirates. The scrapyard is here. But it's more like independent scrap dealers accumulated in one area.

[@VVerVVurm]

My Atari had 1MB of memory and it was a lot! I remember reading in a magazine that althought the CPU was able to address 4GB of memory that this will never happen and extrapolated the power consumption from the 1MB and concluded that 4GB of memory would require about 200 amps during refresh cycle 😆

[@bitsundbolts]

Haha, nice! And now we're considering 4GB unusable.

[@Hinoserm]

Oh hey, I'm the one who makes those Slaton Computers modules you show around 8:45. They're built pretty much the exact same way, but permanently jumpered to EDO -- you can cut a trace and install a resistor if you really want to make them EDO, but I've yet to find anything that can use them that way.

[@kontrolmikro1314]

amazing project....

[@argoneum]

SoundBlaster AWE32 (and AWE64 IIRC) supported 2x 16M modules, but could only use 24MB of RAM for soundfonts. Back in 1990s this was The Ultimate MIDI Setup. SB-Live! / Audigy soundfonts will work with it too. (yes, yes, didn't forget, there was GUS, and Holy Wars wars between some GUS and AWE users, I know ;)

[@OpenGL4ever]

The SoundBlaster AWE32 was released in 1994. But later soundcards where much better MIDI setups. I had a Terratec EWS64XL in around 1997. This was still in the 90s and the EWS64XL was much better than the earlier SB AWE32 and still an ISA card for best compatibility to DOS games.

[@ozzyp97]

​@@OpenGL4everIn fairness, with full ram you can get very nice midi quality out of the AWE32, so long as you chosen DOS game will run under Win9x. Depending on the model they can also have real OPL3 FM, which is a nice perk as well.

[@wigyori]

I recall that those large-capacity modules that You used to source the memory chips from, were used mainly in the HP Netserver series. As all such things, they used to cost a fortune back then - so I'm in a bit of an envy that you've found that lot in the scrapyard. :)

[@bitsundbolts]

I hope to find more since it seems like those modules are in demand. However, I do find those on classifieds websites too (especially in the US). I have no access to those - I need to rely on my scrapyard

[@christophero1969]

Very awesome!

[@bitsundbolts]

Thank you for your support! 🙏

[@DocECS69]

A trip down memory lane! 😀

[@darkfalzx]

My old Packard Bell 486 started out with 4mb, but by the end of its life had 32mb. Since it was all low-capacity SIMMs, I had to use several of them per slot via expansion boards. This was def more than enough for Windows 95, but then I made the mistake of installing Win98 on it…

[@bitsundbolts]

Ohhhh, I remember when I installed windows 95 on my 486. It was such a great experience. I loved it, my PC felt like new. I only used Windows 98 with a Pentium II 350. I never attempted to install it on my AMD 486-DX4-100.

[@darkfalzx]

@@bitsundbolts By the very end I did upgrade it from DX2-66 to DX4-100, but even this didn't make and difference for W98 performance. Should've just downgraded it back to W95. Back then couldn't figure out how to upgrade the video card - would've been fun to see how far I could push it: )

[@michvod]

If I am not mistaken, those 168-pin EDO RAM modules can be very handy in some old Macintosh systems (like PowerMac 7200, etc.). They will also work in Pentium Pro and Pentium II systems, as those also support EDO RAM (the i440FX only supported EDO, later i440LX added SDRAM support, but it supported only 512MB of SDRAM, but 1GB if you used EDO!, same goes for i440BX). Those modules are really rare as we usually think of EDO RAM as an 72-pin SIMMs and not a SDRAM-styled 168-pin DIMM, but those do exist and are really rare

[@richardwernst]

Wonderful!

[@waldmensch2010]

nice work

[@stephenmorrish]

My 386 was an odd ball. A frankin build if you like. 8MB of RAM, but it was all on the main board! No RAM sticks. The motherboard was huge, an ocean of chips. I can't remember the speed of the CPU, but it did have a maths Coprocessor. When everyone had a 486 I was rocking this beastly 386. Pair of 150MB SCSI HDD's, 3" floppy, 5"1/4 floppy, CD-ROM, SB Sound Card & SVGA video card. A full multimedia PC that was a 386 rather than the more typical 486 for the time.

[@ruben_balea]

My first computer (386SX-16 from late 1991) came with 1MB in four 256kB SIMMs and that was more than enough when most games only used conventional memory and only a few could use EMS. Later I got some programs that needed Windows 3.1 in 386 enhanced mode to run and I added another four 1 MB SIMMs to end up with 5 MB.

[@Nukle0n]

My favorite PCB look is black substrate with clear solder mask, so you can see all the copper traces-

[@bitsundbolts]

Ohhhh, interesting... PCBWay has that option... Maybe I should try those.

[@lantapaukku7629]

I had a 386sx25 back in early 90's. I had an ISA card that had 16 slots for 30 pin memory modules and I salvaged a pile of 256kb modules. It gave +4 MB of total memory in addition of those 2MB already on mainboard. Interesting video though.

[@jdmcs]

I'm not surprised that consumer 386 (and even likely some 486) systems that used 30-pin SIMMs had a limit of 64MB when using them. That would have been an *insane* amount of RAM back then, and would have been expensive. The industry largely went to 72-pin SIMMs for higher capacity modules. It's possible that many motherboards were designed such that they could support 16MB modules (if the chipset did), but due to cost and/or availability at the time of release, they only claimed support for 4MB modules. Sill nice to know that some 386 boards out there aren't limited to only 32MB of RAM.

[@wildorb1209]

This is so wild!!!! :-D

[@jefersonfischer]

Very Cool video!

[@bitsundbolts]

Thank you so much for your support! Glad to hear that you liked the video and the project!

[@ajdothack]

Omg I have a ton of scrap arcade boards full whit those ram chips, I am soo going to try this on mi vintage 386 and 486 PCs thank you!

[@bitsundbolts]

You're welcome!

[@HBAVHS]

Hab die Module nun mit KM44V16104 Chips nachgebaut. Kommt wirklich auf den Chipsatz an. Zum Glück hab ich knapp. 100 Motherboards. 🙂 Funktionieren mit: OPTi 495SLC/495XLC - UMC UM8498/UM8496 - SiS 85C471/85C496 - VLSI VL82C486. Dank dir nochmals für das Video. Sehr geil!

[@bitsundbolts]

Wow! Da hast du aber eine ganz schön große Sammlung and Mainboards! Wenn ich dich richtig verstehe, dann haben die Module nicht auf allen Boards funktioniert die du getestet hast, oder?

[@HBAVHS]

@@bitsundbolts Ja. Also nicht auf jedem Board mit 30 Pin Sockel. Kommt halt wirklich auf den Chipsatz an. Ich will die Tage noch die Module in einer Soundblaster AWE testen. Auf Boards mit den oben genannten Chipsätzen liefen sie einwandfrei. Hab sie auch alle mit Check it pro durchlaufen lassen. Ohne Probleme. Ja, bin halt auch schon ein alter Sack mit 56. da sammelt sich schon was an. ;-)

[@itstheweirdguy]

A great video as always! With how much data we can send with our busses on the computers now, it's pretty pathetic how little our computers can do in 2024 taking into consideration we're sending multiple GB/sec even with storage now.

[@JonBrase]

What I'd really like to see for retro machines is an all-in-one storage adapter: SATA connectors and maybe a network port on one side, multiple GB of RAM for caching in the middle, and legacy connectivity on the other side (PATA/Floppy and/or ISA or PCI). Board runs Linux, you connect storage on the modern side, it reads disk images off that storage and presents those images as floppy or ATA disks on the legacy side. There are already SATA/PATA adapters, which allow a modern disk to be presented to an old system, but there are issues with old BIOSes choking on large disks. Using images would allow for keeping presented disk sizes to something BIOS can handle while using the capacity of the underlying modern disk to provide a multiboot environment with multiple legacy OSes without having to squeeze all of them into the size of whatever number of small disks will fit in the chassis.

[@necro_ware]

Nice! That is plenty of memory for such a system indeed. However, I would add buffers to those modules. Bringing VCC down to 3.3V is not enough, the datasheet for those dram ICs says, that the voltage on all other pins also has to be in the same range as VCC, between -0.5V and +4.6V. The chipset on the mainboard will drive the data lines with up to 5V and that could potentially damage the memory modules. Unfortunately there is not a lot of space for an additional buffer, but you could save one voltage regulator and may be bring it to the other side to squeeze three chips onto the PCB. Edit: Ah, just scrolled through the comments and there were already same concerns. I guess, looking excited forward for the next even better revision ;)

[@bitsundbolts]

I finished revision 2.0 with one level shifter and voltage dividers. I'm not sure if the voltage dividers will be able to do the job on the address lines, but if not, revision 3.0 is in the works. All lines go through buffers and should be able to work within specifications.

[@GadgetUK164]

Fantastic work! One potential problem, having to fit 3.3v regulators for 3.3v RAM, the RAM may have a shorter life as any clamping diodes are driven frequently by 5v logic levels of the chipset. It's also possible the chipset could die when interfacing 3.3v and 5v. It's possible the RAM you are using is 5v tolerant? I see you scoped the address and data levels there, and they look right - but probably because of the clamping. It's worth measuring that same way with 5v RAM fitted - see what levels you get. Don't be put off by this btw - the chances are it will work reliably even if the clamping is an issue. It's just one of these things that I am sure will get pointed out.

[@bitsundbolts]

The ram I'm using is not 5V tolerant. In the data sheet it says absolute maximum voltage is 4.75 or something. I am wondering and will do some additional tests before starting a mass order of those PCBs. In case there are 5v signals, would a simple voltage driver be enough?

[@GadgetUK164]

@@bitsundbolts What you might be able to do - since it says the RAM can go up to 4.75v, try measuring the data and address bus levels with a 5v SIMM, lets say the levels are around 4v - that would mean you could perhaps try and regulate the RAM VCC to 4v ish, and in theory the RAM would work safely as its under its 4.75V limit, and clamping would be (I think) less likely as the logic levels are within the VCC level.

[@radionicretrofit]

I wondered same issue, chip lifespan will be reduced with 5v operation. I am not sure how tight timings on address bus but maybe level shifters are fast enough to use on this modules?

[@bitsundbolts]

Would a simple voltage divider do the trick? I might have to get like 40 small resistors on the board if I understand that correctly.

[@bitsundbolts]

I'll try to understand this more. I already got details regarding level shifters. More things for me to learn and definitely a thing to look at before I order larger quantities of those modules. Thank you for all the great hints!

[@joetoney184]

I need to lay out a DDR4 DIMM footprint QDR SRAM board, this video inspired me to get it done! Now I just need to prep my wallet for buying $300 of ebay SRAM to get some low capacity memory to practice soldering down since they are BGA.

[@bitsundbolts]

Glad to hear you found some inspiration! Good luck!

[@AG-jj3lx]

Awesome!

[@Robert.Czarnik]

That's awesome! I have to check my memory connection I have. Maybe I have some of those. If not I'll be interested too.

[@bitsundbolts]

I hope you'll find some of those chips. Making those modules yourself is just so rewarding!

[@Robert.Czarnik]

@@bitsundbolts unfortunately, I don't have those. I'm interested in 4 modules.

[@isaiasprestes]

Back there in 1992, our brand new AMD 386DX40 had 8Mb RAM. At some point, befere acquire a 486DX2, it was upgraded to 32Mb. Running on 8Mb we not really faced lack of memory. With 32Mb, it was such a paradise of RAM. This 386 was active until early 2000s as our local name server, firewall and NAT running Slackware Linux. One day, it's keyboard was not responsive, and I had already an AMD 5x86 spare on the corner. After more than 10 years of work, our beloved 386 (nick named AMaDo, beloved in Portuguese) retired.

[@bitsundbolts]

AMaDo served you well! 32MB is quite a lot for such a platform and probably not that common.

[@JVAmorim]

Very cool!!!! In another project, make a Edo memory!

[@brandonroeder2461]

Neat. I managed to find a 486DX2 66MHz Compaq a while ago and piece together 100MB of RAM for it, maxing it out. I haven't booted it up in quite some time, and I don't know if I have a monitor with a VGA port, or enough converters I can plug end to end. 😅 I inspected it not that long ago and all the caps look ok, and it's been kept dry and clean so it should work. 🤷‍♂️😂

[@Stratotank3r]

Das muss der Hardwarehimmel sein! 386er, die normalerweise 4MB und höchsten 8MB hatten auf 32 und jetzt 64MB zu pushen! Genial. Musste damals meinen 486DLC von 4 auf 8MB aufrüsten und 300DM löhnen. Bin froh, dass ich 4*4MB habe. Bei 486ern dürfte es sicherlich klappen auf 128MB zu kommen. Dazu einen 5X86-133 und Win2000 drauf. Der POD ist zwar besser aber die Boards, die den POD unterstützen, nutzen sicherlich 72pin Module.

[@bitsundbolts]

Ja, diese großen 30-pin Module werden wohl eine kleinere Nische beglücken. Ich werde da auf jeden Fall noch etwas herum experimentieren.

[@TheOldGraff]

Awesome as usual! With this amount of ram you can install some Linux distro in future videos.

[@bitsundbolts]

Although I am not a Linux user, it is interesting that this amount of RAM would allow to run software that would be difficult to use without. I may give it a try. I remember trying out some SuSe distributions long time ago, but I don't remember what version (maybe 7?).

[@TheOldGraff]

@@bitsundbolts I just remember that Linux kernel drop 386 support in 3.8 version so last working kernel is 3.7.10 in theory all distro before 2013 should work. Also I personally want that you run Windows 98 SE and Windows 2000. I know that Windows 2000 work with 486 and 64mb ram but don't know about 386.

[@OpenGL4ever]

@@bitsundbolts I used Linux Slackware 7.0 on my 486DX with 8 MiB. Starting with Slackware 8.0 with kernel 2.4, I had to bake an extra kernel so that I could boot to the command line with the 8 MiB. I couldn't install Debian or Suse, the installer required to much RAM.

[@bbjunkie]

With the responses you're getting i'm sure i'm too late! Just getting into retro computing, would love a set of 4 to use, am addicted to building circuits and bodgery like this!

[@bitsundbolts]

Haha, oh no. Since the PCBs are available to anybody, you're never too late. And I am not selling them now anyway - I just want to see if there is demand for them. The main problem for me would be the logistics to ship modules worldwide due to cost.

[@olek4182]

Back in the day (1990) I had an Amiga 500 with 2.5 MB RAM (which was an incredibly large amount of RAM :) .

[@micksta]

Declaring my interest in such memory modules please :)

[@darklore7566]

That 386 was like umm i am not sure what to do with all this RAM I can only uses about 1/4 of it 😂 like to see the temps of the multitasking with that 386 lol.

[@kjamison5951]

Thank you for this! In theory, my Macintosh SE/30 could easily get its 128MB RAM maxed out!

[@adriansdigitalbasement]

Just awesome! I would love to see if any 386 boards support 128mb on board using 8 of these.

[@bitsundbolts]

Thank you Adrian. I hope to find a board that supports 128MBs!

[@dav1dbone]

A successful and worthwhile project. There were some mainboards from this time that used zipp sockets for memory, do you know of any PCBWay or public domain solutions for an adapter pcb to enable reusing dram from scrap simms to solder onto?

[@TexasAgg2003]

such an awesome video. The black PCBs look great. I can imagine how much something like this would have cost back in the day. besides a ram drive, are there any applications that would have utilized this amount of ram? Maybe some type of simulation software?

[@bitsundbolts]

Thank you! Maybe some industrial applications or CAD software could have utilised such amounts of memory. I wouldn't know what to do with that much memory.

[@sgkonfetti]

Brilliant !!! A++++

[@Bunker278]

I've seen those oddball modules before. The ones I had were in an IBM RISC server I bought back in 2003. It had almost an entire gigabyte of RAM in it. I have no idea what it was used for.

[@robotskirts]

The max amount of memory I had in my 486 SX2 in the 90s was 20 MB. It had come with 8 MB across 8 slots and I had pulled 4 of those and changed them to 4 MB modules. The CPU I swapped with an Evergreen upgrade.