4 ms·

That's exactly what's happening. There are loads of projects going on right now decapping old chips and reverse engineering them. From old CPUs like the 6502

by bcrl 6y ago

That's exactly what's happening. There are loads of projects going on right now decapping old chips and reverse engineering them. From old CPUs like the 6502 to the Amiga Alice chip. It's just a matter of time before most of the retro systems are fully reverse engineered and documented.

deelowe 6y ago
That's generally not what's happening with the mister cores. I haven't looked at all of them, but the ones I have studied are very high level in implementation.
- foldor 6y ago
  To the best of my knowledge, the Neo Geo core has certain chips based on a full decap and implementation in FPGA. Not the entire system though.
  - deelowe 6y ago
    Neat. I'll have to look at that one.
astrange 6y ago
FPGA cores are based on CPU emulators, so they aren't more accurate than the emulator, and decapping a chip doesn't help. FPGAs are written in languages like Verilog that are still high-level and do some probably misguided tricks to make it look like you're programming them with a vaguely C syntax.
- deleted 6y ago
  [deleted]
- pjc50 6y ago
  > FPGAs are written in languages like Verilog that are still high-level and do some probably misguided tricks to make it look like you're programming them with a vaguely C syntax. This is either incredibly badly explained or wrong. Verilog compiles to gate level.
  - astrange 6y ago
    The difference between Verilog and gates is larger than the difference between C and assembly? Also, I think most decapping is done to read data tables out of ROMs, not to figure out what all the gates in a chip do.
- Uberphallus 6y ago
  > FPGA cores are based on CPU emulators FPGA cores are literal CPUs.
  - astrange 6y ago
    Meant to say "FPGA emulators" there, the last emulator project I worked on called them cores.
- bcrl 6y ago
  No, they are not generally based on CPU emulators. FPGA emulators are more accurate than software based emulators, in part because they don't have to do gymnastics to awkwardly emulate things that are easily done in hardware. For example, the documentation for Amiga's custom chips specifies which cycles various DMA activity takes place. Replicating that in hardware is quite easy (just a few comparators wired up to a counter), but it's hugely expensive in software which leads to all kinds of nasty hacks to replicate behaviour games rely on. It's similar with CPUs. CPU manuals from the 1970s and 1980s often specify the exact cycle counts for instructions while having simple bus interfaces and no caches. Coming up with cycle accurate hardware for these CPUs is not all that hard. The Amiga is the last machine I ever had for which I was able to get complete specifications and schematics for and understand completely. Once the 386/486 came along, documentation of SMM mode and other internal details became restricted. Modern computers have so much hidden firmware that understanding the entire system is virtually impossible. In contrast vintage 8/16 (and some 32) bit machines can be completely understood by a single determined individual.

by bcrl 6y ago

deelowe 6y ago

That's generally not what's happening with the mister cores. I haven't looked at all of them, but the ones I have studied are very high level in implementation.

foldor 6y ago
To the best of my knowledge, the Neo Geo core has certain chips based on a full decap and implementation in FPGA. Not the entire system though.
- deelowe 6y ago
  Neat. I'll have to look at that one.

astrange 6y ago

FPGA cores are based on CPU emulators, so they aren't more accurate than the emulator, and decapping a chip doesn't help. FPGAs are written in languages like Verilog that are still high-level and do some probably misguided tricks to make it look like you're programming them with a vaguely C syntax.

deleted 6y ago
[deleted]
pjc50 6y ago
> FPGAs are written in languages like Verilog that are still high-level and do some probably misguided tricks to make it look like you're programming them with a vaguely C syntax. This is either incredibly badly explained or wrong. Verilog compiles to gate level.
- astrange 6y ago
  The difference between Verilog and gates is larger than the difference between C and assembly? Also, I think most decapping is done to read data tables out of ROMs, not to figure out what all the gates in a chip do.
Uberphallus 6y ago
> FPGA cores are based on CPU emulators FPGA cores are literal CPUs.
- astrange 6y ago
  Meant to say "FPGA emulators" there, the last emulator project I worked on called them cores.
bcrl 6y ago
No, they are not generally based on CPU emulators. FPGA emulators are more accurate than software based emulators, in part because they don't have to do gymnastics to awkwardly emulate things that are easily done in hardware. For example, the documentation for Amiga's custom chips specifies which cycles various DMA activity takes place. Replicating that in hardware is quite easy (just a few comparators wired up to a counter), but it's hugely expensive in software which leads to all kinds of nasty hacks to replicate behaviour games rely on. It's similar with CPUs. CPU manuals from the 1970s and 1980s often specify the exact cycle counts for instructions while having simple bus interfaces and no caches. Coming up with cycle accurate hardware for these CPUs is not all that hard. The Amiga is the last machine I ever had for which I was able to get complete specifications and schematics for and understand completely. Once the 386/486 came along, documentation of SMM mode and other internal details became restricted. Modern computers have so much hidden firmware that understanding the entire system is virtually impossible. In contrast vintage 8/16 (and some 32) bit machines can be completely understood by a single determined individual.