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Show HN: We built an 8-bit CPU as 2nd year EE students

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Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#41

Post by CorRupT9 »

pjc50 wrote: post #19

This is also very well documented. Probably as part of the assessment, but it's nice to see. It doesn't appear to have any kind of interrupts, which is quite a limitation for actual usecases, but also makes the architecture much simpler. The use of dual phase clocking is interesting. The document describes it as having the control and data paths operating on opposite phases. I'm curious as to where you got this techn…

Actually this was my very first implementation, even in simulation it had to be made on boards someday keeping timing skew and capacitance of boards in mind i decided to flip the clock, this will give the control unit a head start of half a cycle and get everything ready before the clock reached the next high, this trick was also used in one of the projects I mentioned at last page in the document. I had to probe and check every signal keeping the standard gate delays of 74 series in equation too!

Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#42

Post by CorRupT9 »

dreamcompiler wrote: post #8

"This makes the machine transparent in a way that microcode-based designs cannot be." Every output bit m of microcode can be equivalently expressed as a logic function of n inputs where the microcode has n incoming address lines. This no less transparent than pure logic if you know the contents of the microcode. Microcode is often preferred because changing it is much easier than changing a bunch of gate logic. IMHO…

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Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#43

Post by CorRupT9 »

loloquwowndueo wrote: post #24

So this was all just simulated? Where are the pictures of the build? Back in the day i built a 4-bit CPU on a breadboard (it was huge actually spanned 3 breadboards). Programming the ROM by hand like cavemen (to be fair it was the cave ages). We didn’t carry cameras in our pockets so sadly we didn’t get a picture.

We actually made it on breadboards, since it was hardwired the bread-borad is now a sea of wires everywhere, and some things are not working too. I am thinking of getting a custom PCB just for the control unit to make it presentable.

Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#44

Post by CorRupT9 »

peterus wrote: post #6

Awesome project, re fpga implementation one option you might want to explore are used Bitcoin miner control boards if you want the best logic units/$ ratio. I've used the EBAZ4205 (zynq 7010) control boards with a cheap/generic FT2232HL dev board and it works great. Of course it's a bit more of a pain compared to a regular dev board

This is a nice idea! I never knew of this will look into it. Actually our university did not even provide us with chips to make breadboard version we had to source everything ourselves.

Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#45

Post by CorRupT9 »

wildzzz wrote: post #7
peterus wrote: post #6

Awesome project, re fpga implementation one option you might want to explore are used Bitcoin miner control boards if you want the best logic units/$ ratio. I've used the EBAZ4205 (zynq 7010) control boards with a cheap/generic FT2232HL dev board and it works great. Of course it's a bit more of a pain compared to a regular dev board

If they are taking digital design classes, they'll probably be given something like a DE0-Nano that can run this just fine.

If I tell what we got for our projects you would be disappointed at my university. We get nothing not even a single FPGA kit is available in the whole department.

Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#47

Post by CorRupT9 »

wl wrote: post #12
HerbManic wrote: post #5

With all the talk about developers being lazy and younger folk not understanding the technology they use, it is always great to see examples of core foundational work still being done. Makes the rest of that talk feel like fear mongering.

I did an undergraduate electrical engineering degree some years ago. Building a CPU much like this one was the final project in our second digital design class. The difference here from the usual approach, as they point out, is that this is a gate-by-gate design you could assemble out of 74-series logic gates on a breadboard rather than the more common Verilog/VHDL designs that target FPGAs. Definitely a more tedious…

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Re: Show HN: We built an 8-bit CPU as 2nd year EE students

#48

Post by CorRupT9 »

throwaway2016a wrote: post #38
HerbManic wrote: post #5

With all the talk about developers being lazy and younger folk not understanding the technology they use, it is always great to see examples of core foundational work still being done. Makes the rest of that talk feel like fear mongering.

Every generation in history has said the younger generation is lazy. Didn't make it true when I was a young xenial / millennial and I suspect it's not true for Gen Z and Gen Alpha either.

Actually I am lazy but I love to do what I do and see it through!
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