Introduction and Clock Build - Making an 8 Bit pipelined CPU - Part 1

[@SteveRaynerMakes]

How have I missed this series for three years? I'm looking forward to watching this.

[@weirdboyjim]

Glad you found it. Hope it lives up to expectations!

[@EnsignRho]

Me too. Can't believe I haven't seen it before.

[@PaulDriverPlus]

I completely agree, thank Hack-A-Day for my visits.

[@gradam096]

This is literally what I just said to myself. How has this channel not popped up previously in my searches for homebrew CPUs?? Crazy. Looks like I have a lot of content to watch! :)

[@MrGoatflakes]

Ikr?

[@mikehibbett3301]

I am sooo looking forward to watch all 100 episodes. I cheated and watched episode 100 first, and now I'm hooked! Thank you for such an enormous amount of work you have shared.

[@weirdboyjim]

I hope it doesn't disappoint! My editing improves a lot over the first few videos!

[@Barnardrab]

Episode 100 was my introduction to the channel.

[@KingJellyfishII]

Hmm this is interesting: My name is also James I also watch Julian and Ben I also do game programming (although not professionaly) I am also working on an 8-bit computer

[@weirdboyjim]

Lol! These things happen. How is your computer going?

[@KingJellyfishII]

@@weirdboyjim still in planning stage. I'm making an emulator to make software development (I'm planning on hopefully porting some kind of usable OS to it) a lot easier. I actually started planning it out a few years ago and have been working on the instruction set and core principle (block diagrams etc) on and off. I also have to say that I have almost no experience with any kind of computer stuff on the scale of things as I'm still a child (14) and consequently there's a high likelihood of nothing ever coming of the project. Also since writing the comment I have decided to make it 16 bit and since an OS will need a lot more computer power and therefore clock speed I'm not going to use any breadboards in the final design (if I ever get that far...) EDIT: I suppose something like this, except worse: kzbin.info/www/bejne/Zpu1mKOKpZ2jiJo

[@weirdboyjim]

Sounds interesting, let me know when you make some progress. I'll be doing additional builds in the future, I'm torn between doing a simpler one (As an educational tool for other people to build) and a more complex one with larger registers.

[@KingJellyfishII]

@@weirdboyjim sounds interesting as well. I'd definitely like to see something with a few more bits as in my opinion 8 is a little limiting.

[@pawelczarnecki7780]

This is great, I can’t believe This has been out for three years and I’m just now watching it, how did I miss this.

[@weirdboyjim]

Welcome! Hope it lives up to expectations!

[@pawelczarnecki7780]

@James Sherman it’s awesome 🤩

[@AlexandreGamaLima]

This is by far the BEST channel I've found this year! Really excited to go through the whole series James! Turning into a Patreon right now and I hope you can get many more :)

[@weirdboyjim]

Thanks for the high praise! Hope the series lives up to expectations!

[@dbwt22]

Surprised you don’t have more subs considering the content you make!

[@weirdboyjim]

Thanks. I’ve not been doing it that long (the first half of this series was done “under the radar” with only a few of my friends knowing about it) but I’m actually surprised at how many subscribers I’ve gotten so far. It’s not exactly mass market appeal and there is a lot of quality content in this area already.

[@Aruneh]

Watched all the VGA videos so far, now I’m here. I’ve watched Ben Eaters videos, and even got the kit but gave up and haven’t touched it for a long time because I got frustrated that it didn’t work right. Watching you makes me want to give it another go!

[@weirdboyjim]

Glad you found it interesting. Which of his kits did you get? The thing to do is find ways of testing everything as much as you can as you go.

[@Aruneh]

@@weirdboyjim Both the 8-bit CPU and the 6502. My main problem is not knowing how to fix the issues that I find. I know there is a lot of help to find on eg. reddit, but my patience just ran out. :)

[@nateblanchard2951]

im so glad i found this series i always been wanting to do something like this and glad there someone who will explain it

[@weirdboyjim]

Hope it lives up to expectations!

[@DavidLindes]

The algorithm fed me one of your more recent VGA videos... which looked super cool, but I wanted to watch the origins of how you got to where you were on those (and having seen Ben's videos was not enough, though I have)... I believe I may be watching _all_ of your videos, now, over the coming weeks. :) But I have a suggestion, re 21:23: a foot pedal switch for power! I do normally open, but normally closed could work, too... either way, you can de-power things without having to unplug anything, or even flipping a toggle by hand. Would recommend. :) Hmmm, and perhaps I'll pull the kit I got from Ben back out, and get back to it again....... Here's hoping. :) Thanks for sharing! Expect more comments now and then. :)

[@weirdboyjim]

Foot pedal is an interesting idea for this kind of problem, for a lot of these early circuits a toggle switch on the desk would have been fine. I don't want to spoil anything for you, but over the next 100+ videos I completely fail to resolve this bad habit. Hope you enjoy the series, you've watched some of the later stuff so you know my production standards improve from this early stuff.

[@migry]

A friend pointed me to your videos. I have started from this number 1 and I am working my way through. It is interesting to hear your train of thought. I am puzzled at exactly what you level of electronics knowledge is. You obviously understand computer architecture and the concept of pipelines. I would have though most people attempting to build a TTL computer would keep things simple! :-) In later videos you give hints that you have programmed various micros. One thing I notice which surprised me (although it worked), is that I have always connected LEDs (via a resistor) to +5V, but you use ground instead. OK so LED on is "0" and off is "1" but you can use the open collector 74LS06 inverting open collector device to make a logic "1" input light the LED. I was under the impression that you shouldn't drive LEDs using a logic high (i.e. don't connect the LED to ground). Perhaps modern LEDs need much less current than back in the 80's, so this is not an issue. H-ll when I use SMD LEDs I use a 10k current limiting resistor, whereas back in the 80's the current limiting resistor value of choice was 330 ohm! . As you have shown it obviously works! BTW your use of the resistor SIL is a great idea. No criticism intended!

[@weirdboyjim]

My level of electronics knowledge at the start of this project was very low, I dabbled with a few things over the years but probably 90% of what I have learned is since starting this project, and I've filmed most of that. I know a lot more now that when I started but I believe you are right, I'll stick my cards on the table and explain my understanding. Early logic chips had a transistor to pull down and a resistor to pull up, of course they didn't have a lump of carbon film on the chip, so the "resistor" was actually a leaky half formed gate. Using a high to drive the led meant you were sinking current through that and as you correctly stated the older led's need more. Modern chips may have similar function but they have fully formed gates pulling in both directions, so the direction of higher current doesn't make a difference.

[@Brony22]

coming from the ben eater video series how have i not seen this yet until today. can't wait to watch this :)

[@weirdboyjim]

Welcome! Hope it all lives up to expectations. My production standards start of a little rough around the edges.

[@Brony22]

@@weirdboyjim i don't mind. i enjoy watching these videos either way. someday i want to make my own breadboard CPU. i always enjoyed these kind of electronics because i took a electronics class in school. would have been great to have these videos when i was still in school.

[@TomStorey96]

I use TL7705s in my projects when I need power on reset. They are also voltage supervisors. But the great thing about them is the ability to use external resistors and capacitors to set your reset delay period. They also provide positive and inverted reset outputs. Available in DIP8 so breadboard friendly.

[@weirdboyjim]

I'll take a look at that part thanks. I didn't find it in my searches at the time.

[@TomStorey96]

@@weirdboyjim there are so many of these parts it's not hard to miss them. I think I either came across them by accident or with some obscure search. I really don't remember how I found them, but hopefully they might be of use to you.

[@TomStorey96]

@@weirdboyjim I forgot about feature they have, you can also hook a reset button up to them and it will generate a reset pulse for you as determined by the external RC. I think that's why I liked them so much, they are a bit of an all in one with some nice external controls.

[@RealThunder81]

in addition, a ds1233 also would work

[@gabrielezucchetta4407]

Very interesting, I'll try it in my CPU right away. @TomStorey, do you have an example how setup the circuit with the reset button? I'm not sure how this can be done.

[@cbmeeks]

James from 2018....2021 here. You did it!

[@weirdboyjim]

James from 2018 here, bit late aren't you? surely I finished it this year, or early next at the latest?

[@EdwinSteiner]

Yes, there is a reason for not connecting the Vcc and Vcc1 internally: lead and bonding wire resistance. Devices that monitor power rails often have seemingly redundant "sense" pins (I assume the Vcc1 is such a sense pin). The sense pins are connected to the same traces on the board but they do not draw any significant current (in contrast to supply pins like Vcc), so the voltage drop across the pin, lead, and bonding wire is close to zero. This way the device can get better measurements of the supply rail that are independent of its own current draw.

[@weirdboyjim]

That would make sense, I also wondered if it could be used to monitor a separate power rail.

[@rinner2801]

Looking forward to tucking into this playlist.

[@weirdboyjim]

Hope it lives up to expectations!

[@VK2GPU]

"I have a bad habit of working on circuit boards with the power on" Me too. I need to remind myself not to. I've been soldering bodge wires on a board that I was running and testing code on at the same time this last week....remembering "This is probably not a good idea..."

[@weirdboyjim]

Nice! I’m guessing you were using a power supply without a mains ground? Or is your soldering iron not earthed? I know I shouldn’t work on the circuits while powered but it’s nice to get the immediate feedback. The only thing I’ve broken is a 555 timer when I plugged the power in the wrong way, I guess I could put a few diodes in to protect against that. I’m mostly building with cheap ebay chips so it wouldn’t bother me too much if I had a small attrition rate.

[@VK2GPU]

@@weirdboyjim ~12VAC adapter into my own power supply to give me +/- 12V rails. Soldering iron is earthed I believe. I've busted so many ICs from wrong polarity power, or a wire jumping out of breadboard and with utmost precision hitting the -12V rail. Every bloody time :P Also yay! Cheap ebay chip club!! Most of what I have is from ebay. Sadly some opamps I got were fakes though. Be aware of some jellybean parts, they may just be shit clones.

[@weirdboyjim]

@@VK2GPU I have some good quality parts for the final version of the address registers, this whole project is me learning electronics (if that wasn’t obvious) using my normal “jump in at the deep end” approach. A lot of the logic chips I’m buying look like “new-old” stock, so I do worry the supply will dry up one day. Not had anything fake or bad yet, a few things have simply not turned up but when your paying pennies for chips from China it can be a worth the risk.

[@VK2GPU]

​@@weirdboyjim​I done alright until a set of opamps. Didn't even know they were fakes until I built something that was sensitive to the input pin voltages. Thankfully it was someone on the Synth DIY group on FB pointed me in the right direction. Swapped out for a known good part, worked perfectly. For future I'll prob only use LCSC for most of my resistors, caps, jellybean parts, etc... eBay for the more niche NOS parts. For this project being about learning electronics it seems like you're doing great!! I'm now thinking I should youtube a project I've got burning the back of my mind - building a GPU. I've got a pile of 6502s that I want to turn into a GPU. Why? For the glory of Satan of course!

[@weirdboyjim]

@@VK2GPU That GPU idea is interesting, I’ve thought about doing something similar but using microcontrollers and some discrete logic. Something at the early 3dfx level would be plausible.

[@thoyo]

Awesome project! I remember seeing a more rudimentary version of this on computerphile a few years back.

[@weirdboyjim]

Thanks! There are lots of home made cpu’s out there. I believe that mine is the only pipelined one (at least that I’m aware of).

[@thoyo]

@@weirdboyjim Super cool! You have a new subscriber :)

[@weirdboyjim]

@@thoyo Nice! Hope you enjoy the rest of them!

[@markharrisllb]

I've been listing the parts, the only one I don’t think I've got is the 3470 and the SMD to DIP circuit board. Even my electronics inept brain followed along, though I wouldn’t have been able to find the solutions on my own. A brilliant video, thank you.

[@weirdboyjim]

Hope you have fun playing! Just to warn you I do a different clock design in later vides though,

[@brianwild4640]

Same here how have I missed this good work James 👍🇬🇧

[@weirdboyjim]

Glad you found it, hope it doesn’t disappoint!

[@cosmicrdt]

But what about debouncing the switches? Enjoying so far, will watch the whole series!

[@weirdboyjim]

I’ve not had any bounce issues with the circuit but as I say in the video I pretty much took this from Julians video. I’m still a total amateur at electronics (especially the analogue side of things) but my understanding is that the circuit is partially debounced by the capacitor; the switches are changing the resistances that are trying to charge/discharge it so you need to have contact for a “while” before the transition happens. Bounce is probably possible if you get the timing just right but I don’t see it in practice. I actually plan to do a new clock circuit at some point based of a high frequency crystal and a digital divider, but this is working for now at low clock rates. I hope you enjoy.

[@davidcourtney1398]

I just ran into this video series today, and I was wondering about the debouncing issue also. This clock circuit is certainly more compact, but how do you prevent the switch from causing multiple pulses when pressed? Anyway - very cool stuff. I'm up to Part 4 at this point and will definitely watch the entire series. I finished my implementation of Ben's breadboard version of Malvino's SAP-1 almost 3 years ago. I've started buying more parts because I want to build another one, but this time without all of the 4-bit bottlenecks.

[@wesleymays1931]

It's gonna be a bit of effort for me to watch the whole series. (100 videos - how?)

[@axonxorz]

"probably shouldn't admit to that" Truly an adage for us all

[@weirdboyjim]

Indeed.

[@AlexandreGamaLima]

Thanks!

[@weirdboyjim]

You are welcome!

[@twobob]

solid. nice clock circuit. Liked the smd work. Fun and compact

[@weirdboyjim]

Thanks! That was my first ever bit of smd soldering!

[@electron7373]

Plenty of standard 8 bit CPUs have 16 bit registers. The addition of a pipeline into the 8bit architecture is really interesting.

[@weirdboyjim]

Yeah, you'll usually need at least some registers as wide as your address bus.

[@electron7373]

@@weirdboyjim True. Loving your breadboard CPU series. The pipeline idea is really cool!

[@temurkhamidov1860]

Hello James! Do you mind providing a list of needed physical components to build this? I am highly interested. Amazing work!!! Thank you!

[@weirdboyjim]

I never made a parts list for this, but later in the build I make a more advanced version. The PCB and schematic are available for that.

[@danman32]

I just came across this channel myself. I agree Ben's clock is more complex than probably necessary, but I found a fundamental difference between this and ben's: The single step in this one does a full high/low pulse, whereas in Ben's, you single step the clock transition: push: high, push: low. I can't remember if in Ben 's when you go from clock to single step, output stays at current clock state though. This one clearly does not.

[@weirdboyjim]

I thought Bens' was the same? I've not had hands on with his circuit and I last watched it many years ago. This clock lasted a while but I build a more complex one later in the series.

[@boonedockjourneyman7979]

Were you around the home-brew world in the 1990’s? 16 bit addressable space was an enormous improvement for the very reason you cite. Cynicism is a really bad way to start.

[@weirdboyjim]

Only the tail end, what do you think I was too cynical about? I always cringe looking at these older videos.

[@davidrosset4457]

Is there a substitute breadboard mount chip for the lp3470?

[@weirdboyjim]

I wasn't able to find one which is why I got the little adapter board. There are similar chips though but I wanted to use the same device on breadboard + final circuit. Take a look at the TC1232CPA, it looks like there are smd+through hole versions of that so it might have been a better choice had I known about it.

[@AjinkyaMahajan]

Really appreciate your work ✨✨✨✌💙

[@weirdboyjim]

Thanks! It's encouraging to hear that.

[@benjaminscherrey2479]

Love this series. Which video introduces the ISA?

[@weirdboyjim]

Thanks! The ISA is slowly built up as I add functionality, is there anything specific you are after?

[@damiandassen7763]

Why did you use a whole chip for that single not gate? You could've used a resistor and a transistor to make your own. It takes up less space and it is cheaper.

[@weirdboyjim]

I used 2 of the not gates, one for the clock and one for the reset. Although the real answer to that question is "I didn't know any better", I was very new to electronics when I made that. Still not an expert though, wouldn't it be better to use a pair of fet's to implement a stand alone inverter?

[@damiandassen7763]

@@weirdboyjim oh I see. I am not sure if a transistor or a fet is better, but this setup works for you so I guess that you can keep it. I was just wondering why you used a whole chip. Btw this series is fun to watch.

[@TomStorey96]

@@weirdboyjim you can create an "open collector/drain" inverter using a single transistor and one or two resistors depending on whether you use a MOSFET or BJT as the transistor respectively. I don't really think cost is a great concern at your scale since you aren't building millions of units were saving every cent adds up, and it's more fiddly to do it this way, so no problem to throw in a hex inverter IC IMO. If you really wanted to, when/if you come to build this circuit as a PCB, you could look at the "little logic" series of gates (aka "1G"). They come in 5/6 pin packages usually with just a single gate within, so you can minimise "wastage", but I suspect cost would not be all that significantly different, and the only real benefits might be if you were short on space or had routing constraints as you can sprinkle them around and place them more directly where they are needed on the board.

[@nickwallette6201]

Gotta pick the right tool for the job. If I were designing a circuit on a PCB with SMD parts and such, I might opt for a single transistor inverter, if I only needed the one. But the inverter IC is a full, optimized circuit with characterized speed rating and voltage thresholds, optional open-drain or push-pull outputs, possibly a Schmitt trigger input, and so on. If you have one, and especially on a breadboard where the less complex the better, then you can't go wrong with a fully-baked IC.

[@jimmy21584]

I’d say it’s less effort to just stick in a 50 cent modular part that is standardised, than it is to look up resistor values, gate switching speeds etc. Plus spending a few extra cents to have something that sticks solidly into a breadboard is probably cheaper than hours of debugging bad flying lead connections.

[@edgeeffect]

This looks ACE... I loved Ben Eater's breadboard computer and this looks like you "take it to the next level" I wush I'd had some of this when we were "doing" processor design at college in the 80s........ our CPU was built on the blackboard rather thsn a breadboard which isn't anywhere near as cool as this..... looking forward to watching this whole series.

[@weirdboyjim]

Thanks! I hope you enjoy it.

[@MarkovBitcoin]

Just found your series so starting at ep1. Seems ive got my next month of TV covered. ;) But i have to ask, why would you choose a 555?? There are a lot of clock citcuits out there that allow you to go to much higher speeds, and only need a crystal and a NOT gate or two.

[@weirdboyjim]

The 555 is great for creating variable clocks. I build a new clock circuit later in the series that adds a crystal for high speed running.

[@electron7373]

The 555 shouldn't lock up at power up. Put a 47uF cap where the power pins enter the breadboard and a 0.1uF across 555 pin 1 & 8. Also 0.01uF on pin 5 to ground.

[@weirdboyjim]

If you check the later circuits once I move to pcb I have both the decoupling and the pin 5 cap.

[@electron7373]

@@weirdboyjim Just said that as I thought it might help to eliminate the issue with 555 start up. Not sure if that is the solution in this case.

[@Shyssiryxius]

I have just recently finished the Ben Eater build and my brain is hungry for more. I have read up to the SAP-3 section of Malvinos book but I am sad to see the SAP 2 design skips/assumes the reader knows more than the basics. For instance I doesn't mention what part to use for the 62K ram and 2K rom. I assume this is just a 64K chip but then how it takes 2K for the 'monitor' is left unstated and even how and what the monitor does is also left assumed. Likewise how the instruction register is expanded as well as the program counter are all left up to the imagination as schematics are sadly absent. Im hoping that by going through your videos and by learning as much as possible someone who is new to electronics can overcome these challenges and build something close to what the book describes. Keep up the great work!

[@weirdboyjim]

Glad you are finding this stuff interesting! You are probably right that the "62k Ram" they use is likely a 64k part. I expect they have some address detection logic to switch chip enable. 2K is 11 bits leaving 5bits at the top, NOR those 5 bits together for the ram's chip enable and OR them together for the rom chip enable (Assuming you want ROM in the first 2k of memory). At this point my build has a 32k Ram + 32k Rom configuration which is a little easier with currently available chips, I do have one more memory change planned in a few weeks time that makes that much more flexible. Hope you enjoy the rest of the videos, if you ask questions in the comments I usually reply pretty quickly.

[@captainboing]

"from tiny acorns, mighty Oaks do grow"

[@weirdboyjim]

Not sure I can promise an oak but the circuit definitely get's bigger!

[@joshgray9035]

How does pointer arithmetic work to access addresses above 256 if the alu only supports 8 bit values?

[@weirdboyjim]

It supports a full set of flags so you can do 16bit operations as two 8bit operations.

[@joshgray9035]

@@weirdboyjim thanks for replying, is there a video in the series which describes how this works?

[@patrickrainbolt]

James do you happen to know the part number of your Single pull double through switch you are using. I really like it.

[@patrickrainbolt]

The one with the metal piece that is part of the manual clicker.

[@weirdboyjim]

Those were an ebay purchase, www.ebay.co.uk/itm/153082266200

[@dennisbartello7682]

If it were a chip, you could call it the JSPC01 microproccessor.

[@weirdboyjim]

The next main channel video in a few days will finally reveal the name of this build!

[@dipakpatel-gz1gv]

Hi James Would be great if you put this in kit format, schematics, wiring diagrams. This would be excellent for young students learning electronics. Great stuff ole chap

[@weirdboyjim]

I've had a few requests along those lines. I'll give it more thought when I'm done but this build could be really tricky to implement as a kit.

[@100-pc-notbot]

@@weirdboyjim schematics and a parts list would be wonderful.

[@100-pc-notbot]

ok ok... just a parts list :)

[@megagamingteen]

could say what capacitor and resistor you are using

[@weirdboyjim]

Apologies if that wasn't clear, this is a very old video. I would encourage people starting out with this kind of circuit to experiment. Because of the way the components interact there are many combinations of resisters and capacitors that would produce the same result, and many more that would produce a workable result.

[@rrjmdPA]

Ok, I'm going through your series again for the 3rd time. I find the topic incredibly compelling even though I often feel the explanations wafting through my hair as they pass over my head. It may be because I was born before the space-age (9 when it officially began in 1957); but, I did build my first computer in the 7th grade out of magnetic relays using cardboard to guide a punched cardstock past some bent paper clip contacts to provide the instruction, data and clock pulse. So, in MY mind, I should be able to understand this... or at least enough to say that I did. I see that schematics aren't high on your list. And I know that you do make some alterations to the clock somewhere down the line; and that you did say you have some posting on "Easyeda." But do you know if there's a direct link to your schematic for this post (or the finished clock) - i.e. without having to "join the club" at eda. I really don't have any use for joining their organization beyond looking at your schematic and would rather not if you have any other way, I've enough experience with coding (even in assembly) and building to recognize the incredible talent it takes to do what you're doing - all while wrangling cameras and microphones and cables. I hope to be able to watch you do what you do - until you've covered all there is to cover.

[@weirdboyjim]

Glad you are enjoying it. The easy eda link on the about page should get you to schematics. You shouldn’t need a login just to view.

[@paulchamberlain7942]

If you can feel the explanations wafting through your hair, then you are very close to understanding them. You are far ahead of those for whom the explanations fly so high as to be missed entirely.

[@gelay232000]

How much is the capacitor?

[@weirdboyjim]

From memory I believe that one was 100uf but you can be flexible, the 555 data sheet has a formula and different combinations of capacitor and resistors will produce the same or similar results.

[@TheEmbeddedHobbyist]

Just started watching so i thought i'd better start at the beginning, one question how will the pipe line cope with a jump instruction, were you have to empty the pipe and refill? which is why too much jumping in code slows it down. enjoying the video.

[@weirdboyjim]

I hope you enjoy the series! Well spotted, a pipelined cpu does have to deal with that issue. If you haven't come across it before a term to lookup is "Branch delay slot", some of my branches have this. I don't want to spoil too much here though.

[@TheEmbeddedHobbyist]

@@weirdboyjim Most of my programming is on microcontrollers which never seem to have pipelines. the few programs written on a PC the speed of the processor is way above the response times i required so squeezing the last bit of speed is not worth the effort.

[@sunilpotdar1443]

Which ROM can we use in an 8bit CPU??

[@weirdboyjim]

I started of the 28C16 but i've switched to the 28C256 because it's still a current part. For this kind of work most parallel interface ROM chips will work fine as long as you have enough lines (there are probably some weird devices where this isn’t true). I would make 2 recommendations, check the chip is still available and is marked as “active” on supplier websites. You don’t want to suddenly redesign because you bought some old stock on ebay and nobody makes them anymore. Also make sure that there is good support on device programmers.

[@MarkovBitcoin]

These days i would use an EEprom rather than an classic UV erasable eprom.

[@100-pc-notbot]

has anyone put together schematics for this board?

[@weirdboyjim]

I have most of the schematics on my Easyeda profile.

[@baghayi]

I was expecting you to use a transistor for inverting the signal there.

[@weirdboyjim]

If I wanted to do it without a chip these days I'd probably use a pair of fet's, using a pull up resistor and pull down transistor tends to create a difference between the rising and falling edge that you might want to avoid on a signal you are broadcasting across the entire circuit.

[@cthutu]

Your 8-bit CPU definition doesn't hold water for some other CPUs and it's a bit difficult to define it too. Me, personally, I define it as the size of the main accumulator or main register that receives results. For example, the ALU on the Z80 (which is considered an 8-bit processor) is 4-bit. Also, the Z80 can do computation in 16-bits too (add hl,de opcode for example). So is it 4-bit, 8-bit or 16-bit? In truth, I don't think there's a proper definition and it's pure marketing at the end of the day. Some people say it's the size of the data bus. An example related to this is that we can say the ARM7TDMI on the GB Advance is 32-bit due to the 32-bit registers it uses, but the data-bus is 16-bit (so you needed two fetches to get an instruction from the ROM unless you used the thumb instructions). Is it 16-bit or 32-bit? Fantastic video btw!

[@weirdboyjim]

Yeah, I appreciate it's vague, I did try and get that across but this was my first video, I've got a lot better at collecting thoughts and presenting them now (I won't say good, but I will say better). I just re-watched the start, I didn't really attempt to gave a specific definition, I just said that with an 8-bit alu and 8-bit gpr's mine was really just 8 bit. I can do single cycle 16bit increments and decrements on the address registers though. I was really proud of that "unless you are the marketing department of a 90's console manufacturer" joke at the time *_cringe_* .

[@cthutu]

@@weirdboyjim I think your joke was nearer to the mark ;) I think your design is more 8-bit than most 8-bit CPUs out there.

[@nickwallette6201]

@@weirdboyjim That was spot on, and made me laugh. haha Man... the 90s... when everyone cared so much about an architectural facet that most people couldn't even explain anyway. "It's 32-bit! That's better because it's got more bits!" Uh huh, sure. :-)

[@100-pc-notbot]

@@nickwallette6201 more memory or less wait for a tiny ALU :)

[@nickwallette6201]

@@100-pc-notbot The ALU, yep sure, if you're dealing with multi-byte integers frequently. Could definitely be useful. But memory.. well, the address bus was almost always larger than the data bus, and it wasn't usually the bus size that limited how much memory you could have. :-) Think about the N64. 64 bits! Wow! ...and 4MB of RAM. haha (Granted, the address space would have to accommodate ROM and any memory-mapped stuff as well. Still, hardly bumping into a 32-bit ceiling on that one.)

[@SusanAmberBruce]

Can you name an 8 bit pipelined CPU currently available for purchase?

[@weirdboyjim]

Most modern 8-bit CPU’s are pipelined. Easy example is the AVR chips used in most Arduino’s

[@SusanAmberBruce]

@@weirdboyjim Thanks for your reply

[@jstro-hobbytech]

The caps are running in parallel to ground. The ceramic should be on pin 5. Im years late haha

[@weirdboyjim]

If that's the only thing you found wrong with my first video I'll count myself lucky. That was a silly mistake, can't remember when I found that.

[@retronexusnet]

i love your channel

[@weirdboyjim]

Thanks! I cringe a bit when I watch bits of these older videos, my editing and presentation skill improved over time.

[@retronexusnet]

@@weirdboyjim I also watched the newer ones. And just love the depth of it! Really enjoy watching and learning. please keep up the great contribution!

[@ChandrashekarCN]

💖💖💖💖

[@weirdboyjim]

🤓😉😎😅

[@robinsonchukwu7295]

Please I need direction. How can I get to this level of knowledge of computer system design without a degree

[@weirdboyjim]

There is some great content online now. There is amateur videos like my series but there are also full lecture series from universities that will take you much deeper. My personal recommendation is to either get some chips and breadboards or some circuit simulation software and try building some basic elements yourself, practical experimentation makes learning faster and more interesting than just trying to take it all in directly.

[@nickwallette6201]

I recommend the Falstad Circuit Simulator. It's a tiny Java applet where you get a schematic view of a circuit that you can edit before (and while) you run it, and watch the voltage and current, logic levels, and so on. It's not as full-featured as a full SPICE simulator, but it's leagues easier to use, and I've simulated a lot of circuits on it that I've built successfully afterward. It's my go-to since it's so trivial to test a quick idea.

[@xedover]

take a look at the online course "NAND to Tetris" (and its free)

[@YOLO00005]

Nice

[@weirdboyjim]

Thanks!

[@nickwallette6201]

Ah, this'll never work. ;-)

[@weirdboyjim]

If you asked me back then I might have agreed with you.

[@Realname-k1p]

yo i am 12 this playlist is good if u want learn abour computers

[@weirdboyjim]

Good to hear you found it useful!