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An unusual 7400-series chip implemented with a gate array

righto.com

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Re: An unusual 7400-series chip implemented with a gate array

#31

Post by RetroTechie »

WalterBright wrote: post #24
kens wrote: post #7

Earlier quoted context omitted.

Yes, a ULA is another name for a gate array. A while ago I bought an 8086 chip on eBay that turned out to be a random ULA chip that was re-labeled: https://www.righto.com/2020/08/inside-counterfeit-8086-proce...

I was intrigued, thinking that someone had managed to clone an 8086 with a gate array. What a disappointment.

I've read that some fake sound chips from eBay actually used a gate array. Not original parts, not a 100% equivalent drop-in, but close enough to work & convince most buyers. Don't know if true but sounds plausible. And if so, a (relatively) simple cpu wouldn't be much of a stretch.

Ken's article doesn't mention it, but there's another reason to use a gate array: pre-fabrication, and through that, easier stock-keeping.

Say you have ~100 different IC's like the one described. One could then do all the manufacturing steps to produce eg. 100k of those gate arrays, except the last fabrication step. And possibly keep a large stock of those 'blank' gate arrays.

Then (when it's known which of those 100 IC's is needed), apply only the last production step to those 'blanks', and presto: selected IC ready - in large volume if needed. Or produce IC's where original part has become hard-to-find.

For a mil-spec part, that flexibility might be among reasons to go for a gate array.

These days, something like a fuse-based FPGA might be used instead?

Re: An unusual 7400-series chip implemented with a gate array

#32

Post by kens »

ekimehtor wrote: post #29

I know it's not adding very much to the conversation but I just have to give kudos to the author of this article. It's always nice to see what the magic smoke inside those chips look like before I let it out! So great job I look forward to reading more of your articles!

Thanks! I'm glad you enjoyed the article.

Re: An unusual 7400-series chip implemented with a gate array

#33

Post by kens »

RetroTechie wrote: post #31
WalterBright wrote: post #24

Earlier quoted context omitted.

I was intrigued, thinking that someone had managed to clone an 8086 with a gate array. What a disappointment.

I've read that some fake sound chips from eBay actually used a gate array. Not original parts, not a 100% equivalent drop-in, but close enough to work & convince most buyers. Don't know if true but sounds plausible. And if so, a (relatively) simple cpu wouldn't be much of a stretch. Ken's article doesn't mention it, but there's another reason to use a gate array: pre-fabrication, and through that, easier stock-keepin…

> Ken's article doesn't mention it

See footnote #5 :-)

Re: An unusual 7400-series chip implemented with a gate array

#34

Post by hyperman1 »

colanderman wrote: post #18
hyperman1 wrote: post #9

Funny to see this appear online today. I was discussing the real nand2tetris computer built from 74 ICs yesterday with my 8 year old son yesterday: https://hackaday.io/project/185131-the-hack-computer-from-na... and now this pops up. I'm thinking of buying a bunch of 74xx ICs and buttons and led+resistors somewhere and let him mess with them. It's stone age digital tech according to current norms, but I'd rather see…

Vintage X-in-1 kits. Particularly the 300-in-1 kit had a breadboard and a bunch of logic chips. 500-in-1 similar but even has a microprocessor.

I owned a 200 in 1 as a kid, and spent a lof of time playing it. I've never really looked at the others.

The 300 in 1 is indeed a level up. I'll think about it.

Re: An unusual 7400-series chip implemented with a gate array

#35

Post by RetroTechie »

kens wrote: post #33
RetroTechie wrote: post #31

Earlier quoted context omitted.

I've read that some fake sound chips from eBay actually used a gate array. Not original parts, not a 100% equivalent drop-in, but close enough to work & convince most buyers. Don't know if true but sounds plausible. And if so, a (relatively) simple cpu wouldn't be much of a stretch. Ken's article doesn't mention it, but there's another reason to use a gate array: pre-fabrication, and through that, easier stock-keepin…

> Ken's article doesn't mention it See footnote #5 :-)

Ah, righto! Also I see you elaborated more on this aspect in article on that fake 8086. For anyone interested:

https://www.righto.com/2020/08/inside-counterfeit-8086-proce...

As always: great stuff!

Re: An unusual 7400-series chip implemented with a gate array

#36

Post by phibz »

RetroTechie wrote: post #35
kens wrote: post #33

Earlier quoted context omitted.

> Ken's article doesn't mention it See footnote #5 :-)

Ah, righto! Also I see you elaborated more on this aspect in article on that fake 8086. For anyone interested: https://www.righto.com/2020/08/inside-counterfeit-8086-proce... As always: great stuff!

Ken's footnotes are usually my favorite part of his articles!
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