Running the Cx/Tx 486DLC to the Limits! 386 replacement CPU with 1KB L1 Cache. Insane results!

[@philscomputerlab]

Amazing 😮😊

[@atheatos]

Thank you! I checked you video on this topic also a few days ago. It is nice you are also checking older platforms now.

[@philscomputerlab]

@@atheatos I've started doing a bit of research and Oh My there are so many variants and versions to explore. Very interesting but also confusing! Some seem to be Cyrix CPUs in disguise and other interesting nuggets of details.

[@atheatos]

I have now also the 486SXL2 (8KB L1 version of the 486DLC). Managed to run this also at 55MHz and 80MHz+ (X2 mul). The performance is very 486 like... ok with the limitation of the ISA VGA. I do not know when I will have the time to make this video. Quite busy these days :/

[@philscomputerlab]

@@atheatos Amazing! The clock doubled ones are really hard to find it seems.

[@atheatos]

yeah it is nearly impossible to find the 486sxl2 132p (386 socket) version, I do not have this either. But there is also a 168p (486 socket) one. It is way easier to find this one and I have made an adapter to 132p for this. I also have now the rare 486Drx2 (486DLC with x2 mul), not tested this one yet.

[@Pulverrostmannen]

I been overclocking every computer possible since the 90s, I love the extra free performance hiding inside my stuff :)

[@atheatos]

Same here. Unfortunately, overclocking is a bit dead these days. CPU come now OC from factory.

[@Pulverrostmannen]

@@atheatos​​⁠ there is still overclocking capabilities in more modern chips. My last gaming computer has a 6700K cpu which I overclocked to 4,8Ghz with all cores loaded and generally it won’t turbo when all cores are loaded reducing performance. This specific cpu outperformed a 7700K with the OC I made. Now I have the Ryzen 7 5800X I have made it able to turbo up to 5GHZ which is a substantial performance increase too. However it’s not as straight forward to OC today VS older stuff

[@DanielLopez-up6os]

Another Amazing Video man!

[@atheatos]

Thank you! I have now beaten again all my scores. I will just make a final video with all this. Then I will move to an other M/B and 486 stuff.

[@UncleMikeRetro]

Nice video! I have one of the Cyrix 486 DLC 40 MHz chips myself but the clock battery ruined part of my 386 motherboard before I could rescue it. Great stuff you have here.

[@atheatos]

So sad :(

[@UncleMikeRetro]

@@atheatos Ah... I still have to test the board. I might just have to live with an inaccurate clock is all. Again, glad I found your channel!

[@atheatos]

Thank you, I subbed to you too. I see many interesting Vids. :)

[@necro_ware]

Very interesting results, thank you very much! Would be funny to see, how you boil the water on the CPU at 55MHz :D It get's damn hot... By the way, I tested the CPU in two other 386 boards and everywhere the L1 cache was not reported in the benchmarks as well, though it was measurably working. Thumbs up!

[@atheatos]

Thnx :) I have this 35x35x22 passive cooler on top with some MX-4. looks ok, not that hot. Now because I am also pushing this, I have a 120mm case fan on top of the M/B. Not a permanent solution, but it runs very cool in the end. In general I do all this to have fun with Modding, OC and Benches. No time to use these are real systems. BTW I put your video in the description also. Your results are very similar to mine at 40MHz! You have a very nice system! You only lose in Quake due to the IIT FPU.

[@necro_ware]

@@atheatos Yes, I remember your advice with another co-pro. I have a Cyrix 3C87-40 here as well, but didn't have time to try it out. Too many projects :D And thanks for mentioning my video. Cheers!

[@DKJones96]

Interesting indeed. I put the TX486DLC into my motherboard(same M326 as here) and it doesn't see the L1 cache either, however, with a CX486DRx2/66 in there cachecheck does exactly what you would expect. Strange as they are both 1KB L1. I also only get 1FPS better in 3DBench with that 66 chip over the SLC clocked at 50MHz. Too bad the DRx doesn't overclock well.

[@atheatos]

Good to hear this. Very interesting! Yeah I noticed you have exactly the same M/B :) You can use now all my Bios opts :) The no1 question is if it is possible to disable the x2 multiplier. (maybe with the command cyrix -c, or cyrix -cd) Then what is the maximum Bus? Is this limited by the M/B or the CPU? We also need a comparison of TX486DLC 50Mhz to CX486DRx2/66 (2x mul) same M/B, ISA clock, mem. If possible, a comparison of TX486DLC and CX486DRx2 same M/B, clock, mul. Please check all these and make a video or two!! :) CX486DRx2 is very rare and it is totally improbable I will get one.

[@DKJones96]

@@atheatos I hadn't put this away yet so I'm playing with it at the moment. I don't see a way to disable the 2x multiplier. I have two different utilities on here and neither of them make any mention of it. Tried switching a couple of registers that they don't really label and it just locks the machine up. At some point I wear I saw someone mention a register for control of the multiplier but my Google-Fu fails me now.

[@djpirtu2]

I have Ti486SXL-40 (8KB L1) in my Toshiba T5200, it really made difference to original 386DX/20 and it has that 2x multiplier.

[@atheatos]

Sure the difference there, should be huge. The 8KB cache is also very important. I still do not have the Ti486SXL, it is a very rare chip. But I have some 486sxl2 chips (this is the SX 16bit variant), I will play with these soon.

[@michaelturpen5159]

If either Cyrix or TI had made a product like the Intel RapidCAD, but with the 486 instructions enabled and at least 1KB of cache, it would have been quite the successful upgrade for many AutoCAD users that couldn't afford to get a 486DX system. It would have thrashed the RapidCAD on integer performance, and with Cyrix' FPU know-how (at least, until they just started sitting on their laurels), they'd have captured that market for a while.

[@atheatos]

You are right! I think Cyrix missed this opportunity! Yea this is funny... Cyrix 386 replacements have 486 instructions and L1 so these are strong with Int but weak with external FPUs (especially the x2 ones are very slow). RapidCad is the complete opposite. RapidCAD, another CPU I wish I had :( I really want to see this overclocked!

[@michaelturpen5159]

@@atheatos I know Intel didn't want to kill sales of the 486, but they could have sold more RapidCADs if they'd been smart about it (and it could have then almost guaranteed the 486 or Pentium sales based on buyers' satisfaction with that product). I wonder if many found it more cost-effective to upgrade to the Cx or TI offerings because the machines they went into weren't always running AutoCAD.

[@atheatos]

I agree, The only thing I am not sure is if Intel could actually do this. Adding L1 support in a 386 M/B is not trivial. And Cyrix actually patented their methods. Maybe a 2x version of the rapidcad :)

[@michaelturpen5159]

I'd made a comment earlier and it got eaten (and now it says there are 5 when it's just mine and Necroware's comments). Had some information about the cyrix command line that should make that L1 cache visible in speedsys 4.28 and cachechk; I'll try to post that again once I verify my commands do make a difference in both what those tests reveal and any boost in the landmark/doom/quake performance

[@michaelturpen5159]

cyrix -e -f- -b -m -xA000,128 -xC000,256 speedsys shows the L1 8KB cache, 35.72MB/s; L2 256KB 31.56MB/s; aggregate throughput 20.68MB/s It's the "moving" part of the graph that shows that 8KB in action.

[@atheatos]

Yea this will enable the Barb input. I have tested all these on my machine. Does not make any difference no mater what I do with these inputs. Either every M/B is different and/or the SXL is different and the 1KB cache of the DLC is to small to be detected by the tools, I do not know. Either-way the 1KB L1 cache here looks like is is working. So how are my results? I am probably beating the SXL at everything right?

[@michaelturpen5159]

@@atheatos I know if I set my settings wrong that 8KB doesn't show up in speedsys, and I'm not sure why it doesn't show up in cachechk no matter what I do. My Excel sheet is all over the place on my tests. One of them shows SuperScape 1.0 at 25, 1.0c 24.6, Landmark 6.0 CPU 167.82/FPU 164.5 Quake timedemo took 377.3 seconds This was with the TI486SXL with only 16MB I think this was with DRAM set for 180 or maybe 240 (but when the DRAM refresh is too long, floppy disk reads will be very slow or just time out)

[@michaelturpen5159]

It dawned on me that maybe if the BIOS setting on your motherboard is set to Cyrix CPU enabled, that it will override the Cyrix utility. Lots of reboots to test that theory! I know that my own system is unstable if I let the BIOS handle it entirely.

[@atheatos]

My Bios has no special options for Cyrix in the menu. The Bios has some default values for the resisters that are more or less ok. I can change the default values with ModBin. Now when I used the tool, the settings are definitely overwritten by it. I checked with Cyrix -q. Also other options have an effect. The Flush, Barb options defiantly have no effect on my M326 + 486DLC. I have no dough that these are important with other M/Bs.

[@michaelturpen5159]

Oh, hey, have you seen THIS? v=DlxlOtupnUc "386DX-40 runs Quake III Arena using Open GL and 64MB RAM" (not sure if I should try to use the full URL, so it's basically just the v= portion of a normal KZbin URL). M326 v5.3 with 64MB by putting in four 16MB SIMMs. I wonder if the M321 would work with eight 16MB SIMMs. (Probably only the first 32MB would be cached, but careful location of a RAM drive to keep programs in the cacheable area could give a speed boost).

[@atheatos]

That is nuts! I have places to make a video like that actually. For My M326 the maximum is 8 x 4MB =32MB. (according to the manual) I do not have 16MB simms to test. The caching thing... you are probably right.

[@michaelturpen5159]

@@atheatos Did 64MB 30-pin SIMMs exist when the M-321 or M-326 was designed? Because each SIMM has 12 address lines, there's nothing inherently special about 16MB SIMMs other than having to have been quite expensive when new (and maybe expensive now, thanks to scarcity). Your mission, should you choose to accept it, is to make 45ns, 16MB 30-pin SIMMs ;)

[@atheatos]

64MB simm30? I do not think so. 16MB simm30 probably possible to make. I have to search for chips. I have seen some M/Bs officially supporting these, while other top at 4MB simm. Yea it is all about the chipset and whatever the 12th address line is rooted. I do not know how useful these would be... Maybe only for 486s. The bigger the chip the slower it gets. 45ns no way! With a bit of luck I might find 50ns chips.

[@michaelturpen5159]

d'oh I meant 16MB. Obviously, 16MB is the maximum since there are only 12 address lines

[@joelavcoco]

@@michaelturpen5159 16M 30-pin SIMMs do exist, and can be used to get a Mac Quadra 700 to 68M (4m soldered onto MB) of RAM. You can still buy them at Other World Computing for $12 each. Should work on PC unless you need parity bit.

[@djpirtu2]

Got myself a 100MHz oscillator but my 486DLC-33 just wont make it up to 50MHz 😅 It boots to DOS but really unstable. Tried to play with all wait state settings but nothing helps... Need another contestant.

[@djpirtu2]

Got it working! Just needed a fan to blow on the CPU and mobo 😆 In BIOS needed to set 1WS for the memory R/W. Doom low detail 1529 realtics. ISA-bus clock 12,5MHz because my ET4000 just won't take more. This baby runs FastDoom in VGA-mode (13h) quite well. 3DBench 1.0c gives 27,4. Edit: it was one of the cache chips which started failing after heat-up, swapped it and now it's stable without fan @50MHz. So, maybe 55MHz next but I think I'll need that any_clk for that. 😅

[@pointblank722]

Do bios have to identify the Cyrix cpu for the operation?

[@atheatos]

No, these are are drop-in replacements for 386DX. However enabling the cache without problems depends on the M/B circuits. And a bios that is aware of CPUs like that could save you from having to use the Cyrix tool.

[@run4restrun259]

How much it cost? It seems there is no sense do upgrade to Cyrix :)

[@atheatos]

The 486DLC is not that expensive or rare. Max 20e total with shipping. Especially the Texas Instruments Chip. The other models... forget it.