4 ms·

Build an 8-bit CPU from scratch

54 points by punnerud 6y ago

MaxBarraclough 6y ago
What's the legal situation of the 6502? Would there be risks in making them at scale?
- kens 6y ago
  The 6502 has a patent on decimal addition (#3,991,307), but that's long-expired. MOS Technology got sued by Motorola for making the 6501/6502 because they violated Motorola's patents on the 6800 and took trade secret documents. IC masks are protected as of 1984 (mask work is essentially copyright for the die), but the 6502 predates that. Some companies (such as Intel) copyright the assembly-language mnemonics, but that wouldn't be an issue. I can't think of other issues with the 6502 but I'm not a lawyer. Note the MOnSter 6502, a copy of the 6502 built from discrete transistors. I should also point out Ben Eater's 8-bit CPU is a simple design, not a 6502.
  - userbinator 6y ago
    IC masks are protected as of 1984 (mask work is essentially copyright for the die), but the 6502 predates that. ...and the copyrights for masks are much shorter than traditional copyright - only 10 years in the US: https://en.wikipedia.org/wiki/Integrated_circuit_layout_design_protection https://en.wikipedia.org/wiki/Integrated_circuit_layout_desi...
- colejohnson66 6y ago
  Well, Ben Eater isn’t the one making them, but Western Design Center (WDC, no relation to WD) who supposedly owns the rights to produce them. Eater is just reselling them which is allowed under the “first sale doctrine”
  - segfaultbuserr 6y ago
    > Western Design Center (WDC, no relation to WD) who supposedly owns the rights to produce them. The founder of WDC, Bill Mensch [0], was one of engineers from the original 6502 team at MOS Technology. [0] https://en.wikipedia.org/wiki/Bill_Mensch https://en.wikipedia.org/wiki/Bill_Mensch
    - colejohnson66 6y ago
      Well that certainly explains it. I never knew that
fernly 6y ago
Ben Eater's pedagogy is top-notch for sure. But there are others out there. One worth noting is James Sharman[1] who has constructed a completely new, self-designed 8-bit CPU that features a two-stage instruction decode pipeline, and is currently adding scratch-built peripherals to it. [1] https://www.youtube.com/c/weirdboyjim https://www.youtube.com/c/weirdboyjim
- sitharus 6y ago
  I really appreciate Ben Eater's production values. He doesn't gloss over mistakes, but it's not just a direct recording of experiments. His videos have a definitely planned direction and it makes it much easier to watch.
iHegazy 6y ago
Anyone's got an idea why the 6502 is more harder to find than the Z80 ? Can't find them at any of my local electronics stores where i live for some reason unlike the Z80s which i find plenty of.
- Jedd 6y ago
  I think the 6502 was less 'general purpose' than the Z80 (which I've seen huge banks of in Honeywell FEP's, years ago, f.e.). I imagine they're similarly sought-after now, though. I've never played with the Z80, so I don't know if it offers easier integration with arduino / RPi and other basic systems now. FWIW I see they're available on local ebay for few dollars: https://www.ebay.com.au/itm/273461107051 https://www.ebay.com.au/itm/273461107051 (I think the 6502A means it runs at 1.5MHz, but don't quote me on that.)
  - duskwuff 6y ago
    Yikes. That's a remarked part -- the style of printing on the top is wrong, and the date code is nonsense. (0448 would indicate it was manufactured in late 2004, but Rockwell Semiconductor was spun off as Conexant in 1999, and they stopped manufacturing this part many years before that.)
    - Jedd 6y ago
      Oh, that's interesting (and way outside my knowledge bubble). You reckon it would actually work as a 6502, or it's remarked from an entirely not-65xx CPU?
      - duskwuff 6y ago
        There's a decent chance it's actually a 6502, but the actual part that's under those markings could be any one of a number of 6502s from many different manufacturers.
      - segfaultbuserr 6y ago
        Both are possible. I guess there's a 70% chance that the chip is not a 6502 at all, nevertheless still a 30% chance that the chip is salvaged from trash and remarked but its silicon die is authentic.
roninkoi 6y ago
Another cool project is the Magic-1 [1], which is also well documented. It even runs Minix! [1] http://homebrewcpu.com/ http://homebrewcpu.com/
dang 6y ago
https://news.ycombinator.com/item?id=21902281 https://news.ycombinator.com/item?id=21902281 Also, from 2017: https://news.ycombinator.com/item?id=14883776 https://news.ycombinator.com/item?id=14883776 https://news.ycombinator.com/item?id=14450945 https://news.ycombinator.com/item?id=14450945

54 points by punnerud 6y ago

MaxBarraclough 6y ago

What's the legal situation of the 6502? Would there be risks in making them at scale?

kens 6y ago
The 6502 has a patent on decimal addition (#3,991,307), but that's long-expired. MOS Technology got sued by Motorola for making the 6501/6502 because they violated Motorola's patents on the 6800 and took trade secret documents. IC masks are protected as of 1984 (mask work is essentially copyright for the die), but the 6502 predates that. Some companies (such as Intel) copyright the assembly-language mnemonics, but that wouldn't be an issue. I can't think of other issues with the 6502 but I'm not a lawyer. Note the MOnSter 6502, a copy of the 6502 built from discrete transistors. I should also point out Ben Eater's 8-bit CPU is a simple design, not a 6502.
- userbinator 6y ago
  IC masks are protected as of 1984 (mask work is essentially copyright for the die), but the 6502 predates that. ...and the copyrights for masks are much shorter than traditional copyright - only 10 years in the US: https://en.wikipedia.org/wiki/Integrated_circuit_layout_design_protection https://en.wikipedia.org/wiki/Integrated_circuit_layout_desi...
colejohnson66 6y ago
Well, Ben Eater isn’t the one making them, but Western Design Center (WDC, no relation to WD) who supposedly owns the rights to produce them. Eater is just reselling them which is allowed under the “first sale doctrine”
- segfaultbuserr 6y ago
  > Western Design Center (WDC, no relation to WD) who supposedly owns the rights to produce them. The founder of WDC, Bill Mensch [0], was one of engineers from the original 6502 team at MOS Technology. [0] https://en.wikipedia.org/wiki/Bill_Mensch https://en.wikipedia.org/wiki/Bill_Mensch
  - colejohnson66 6y ago
    Well that certainly explains it. I never knew that

fernly 6y ago

Ben Eater's pedagogy is top-notch for sure. But there are others out there. One worth noting is James Sharman[1] who has constructed a completely new, self-designed 8-bit CPU that features a two-stage instruction decode pipeline, and is currently adding scratch-built peripherals to it. [1] https://www.youtube.com/c/weirdboyjim https://www.youtube.com/c/weirdboyjim

sitharus 6y ago
I really appreciate Ben Eater's production values. He doesn't gloss over mistakes, but it's not just a direct recording of experiments. His videos have a definitely planned direction and it makes it much easier to watch.

iHegazy 6y ago

Anyone's got an idea why the 6502 is more harder to find than the Z80 ? Can't find them at any of my local electronics stores where i live for some reason unlike the Z80s which i find plenty of.

Jedd 6y ago
I think the 6502 was less 'general purpose' than the Z80 (which I've seen huge banks of in Honeywell FEP's, years ago, f.e.). I imagine they're similarly sought-after now, though. I've never played with the Z80, so I don't know if it offers easier integration with arduino / RPi and other basic systems now. FWIW I see they're available on local ebay for few dollars: https://www.ebay.com.au/itm/273461107051 https://www.ebay.com.au/itm/273461107051 (I think the 6502A means it runs at 1.5MHz, but don't quote me on that.)
- duskwuff 6y ago
  Yikes. That's a remarked part -- the style of printing on the top is wrong, and the date code is nonsense. (0448 would indicate it was manufactured in late 2004, but Rockwell Semiconductor was spun off as Conexant in 1999, and they stopped manufacturing this part many years before that.)
  - Jedd 6y ago
    Oh, that's interesting (and way outside my knowledge bubble). You reckon it would actually work as a 6502, or it's remarked from an entirely not-65xx CPU?
    - duskwuff 6y ago
      There's a decent chance it's actually a 6502, but the actual part that's under those markings could be any one of a number of 6502s from many different manufacturers.
    - segfaultbuserr 6y ago
      Both are possible. I guess there's a 70% chance that the chip is not a 6502 at all, nevertheless still a 30% chance that the chip is salvaged from trash and remarked but its silicon die is authentic.

roninkoi 6y ago

Another cool project is the Magic-1 [1], which is also well documented. It even runs Minix! [1] http://homebrewcpu.com/ http://homebrewcpu.com/

dang 6y ago

https://news.ycombinator.com/item?id=21902281 https://news.ycombinator.com/item?id=21902281 Also, from 2017: https://news.ycombinator.com/item?id=14883776 https://news.ycombinator.com/item?id=14883776 https://news.ycombinator.com/item?id=14450945 https://news.ycombinator.com/item?id=14450945