3 ms·

While I know a lot of these projects try to use period components, it'd be neat to see one of the later 486's used since they're 3.3V. It would allow you to use

While I know a lot of these projects try to use period components, it'd be neat to see one of the later 486's used since they're 3.3V. It would allow you to use a modern FPGA for all the glue logic without bus voltage conversion.

dash8 6y ago
The S-100 bus only outputs +8V, -18V and +18V. The idea is that the board itself will convert this voltage to what the components on the board needs to operate. The newly designed board have a newer voltage regulator that outputs 5V and the optional 3.3V from the higher voltage provided by the S-100 bus. You always need to do a voltage conversion on a S-100 card.
- Teknoman117 6y ago
  Oh, S-100 signal voltages are at 8V, and +/- 18V?
emh68 6y ago
I've been working on something like that (actually with a Pentium), but the biggest problem is finding an FPGA with enough pins to connect to the CPU, RAM, peripherals, etc. Maybe I need to use a cheaper FPGA to mux down the 64-bit-wide data bus (which this one seems to do with a CPLD). No matter how you cut it, it quickly becomes a pretty hairy design.
- Teknoman117 6y ago
  Oh nice. It would be really awesome to see a homebrew socket-7 or super socket-7 system. The only thing that comes to mind that's not stupid expensive would be getting a PCB manufacturer to solder a 500 or 700 pin Lattice ECP5(-5G) FPGA to a board for you (the FPGA in single units is like $60). You can use the trellis/nextpnr open source toolchain with those. You'd probably need a 6 or more layer board, which isn't the cheapest thing... I'd been doing a M68K board with an ice40. I got some 68010's with the intention of implementing an MMU for funzies. Maybe try to boot Linux (sloooowly) on it. Got side tracked with a different project I thought would be more useful for people :)
- userbinator 6y ago
  I thought the Pentium was the start of not (publicly) documenting CPUs enough that anyone could build a computer around one?
Teknoman117 6y ago
since I can't edit the comment anymore by "bus voltage conversion" I meant signal level conversion.

dash8 6y ago

The S-100 bus only outputs +8V, -18V and +18V. The idea is that the board itself will convert this voltage to what the components on the board needs to operate. The newly designed board have a newer voltage regulator that outputs 5V and the optional 3.3V from the higher voltage provided by the S-100 bus. You always need to do a voltage conversion on a S-100 card.

Teknoman117 6y ago
Oh, S-100 signal voltages are at 8V, and +/- 18V?

emh68 6y ago

I've been working on something like that (actually with a Pentium), but the biggest problem is finding an FPGA with enough pins to connect to the CPU, RAM, peripherals, etc. Maybe I need to use a cheaper FPGA to mux down the 64-bit-wide data bus (which this one seems to do with a CPLD). No matter how you cut it, it quickly becomes a pretty hairy design.

Teknoman117 6y ago
Oh nice. It would be really awesome to see a homebrew socket-7 or super socket-7 system. The only thing that comes to mind that's not stupid expensive would be getting a PCB manufacturer to solder a 500 or 700 pin Lattice ECP5(-5G) FPGA to a board for you (the FPGA in single units is like $60). You can use the trellis/nextpnr open source toolchain with those. You'd probably need a 6 or more layer board, which isn't the cheapest thing... I'd been doing a M68K board with an ice40. I got some 68010's with the intention of implementing an MMU for funzies. Maybe try to boot Linux (sloooowly) on it. Got side tracked with a different project I thought would be more useful for people :)
userbinator 6y ago
I thought the Pentium was the start of not (publicly) documenting CPUs enough that anyone could build a computer around one?

Teknoman117 6y ago

since I can't edit the comment anymore by "bus voltage conversion" I meant signal level conversion.