4 ms·
Really, the best way to solve this is likely with FPGAs, not ASICs. If you're not using an original chip, does it really matter if it's an FPGA or not? Already,
by monoideism 6y ago
Really, the best way to solve this is likely with FPGAs, not ASICs. If you're not using an original chip, does it really matter if it's an FPGA or not? Already, most of these reproduction PCB projects, including this one, end up using PLDs to replace hard-to-find specialied ICs (and even those PLDs are at risk of EOL). So it's not like they're using 100% original chips, anyway.
I understand the urge, but unless the cost of ASIC manufacturing drops dramatically, I don't see this as being practical for small runs like hobby reproduction boards.
Edit: I forgot to add: this is impressive work, nonetheless!
- zeckalpha 6y agoFurther in the article, there’s a discussion of replacing custom PAL logic with modern Atmel chips.
- monoideism 6y agoI mentioned that ("including this one"). Problem is, they're Atmel chips that are still in production, but I wouldn't call them "modern". Most competing PLDs are now out of production, and it wouldn't surprise me to see the atmel f16v8 series follow. More and more people just use cheap CPLDs or FPGAs (which unfortunately aren't available in DIP packages and so not pin compatible with the old custom ICs used in the 80s).
- throwaway2048 6y agoits pretty easy to make SMT to DIP adapter PCBs, doesn't work with large chips, but a small FPGA is all you need for such old ASICs anyways. http://www.the8bitguy.com/wp-content/uploads/2018/05/SwinSID-Ultimate02.jpg http://www.the8bitguy.com/wp-content/uploads/2018/05/SwinSID...
- hakfoo 6y agoI suppose it depends on how you're using FPGAs. It seems like a lot of the FPGA products-- things like MISTer-- are system-level emulators, which rarely provide full legacy I/O breakout. You can emulate a complete 68k Mac on a FPGA, but where do you attach that weird NuBus card? Now, replacing individual chips with FPGAs/PLDs is likely to retain that, although I could imagine it's a lot less forgiving of an emulation, when it has to match the analog-domain properties of the original chip somewhat.
- monoideism 6y ago> You can emulate a complete 68k Mac on a FPGA, but where do you attach that weird NuBus card? I just looked, and NuBus has 96 pins with clock rate of like 20 MHz. There are FPGAs with > 500 GPIO that can easily handle that clock rate, and ones with over >200 GPIO that are fairly affordable. Now, I mess around with FPGAs, but I'm not an electrical engineer, and there may be other issues. But it seems doable. Any electrical engineer and/or hardcore FPGA hacker want to chime in?
- NovemberWhiskey 6y agoIt also looks like at least 30-40 of the pins on NuBus are either grounds or power supplies, so it's not even as bad it seems.
- monocasa 6y agoYeah, those wide parallel connections were pretty much universally power/ground heavy for signal integrity reasons.