keenerb wrote:Forgive me if this is an absurd question.
I've seen Commodore 64 FPGA emulators, and a basic Intel/8088 FPGA implementation as well. Would a decent FPGA have the horsepower necessary to run Adlib/Soundblaster emulation? Would it be able to interface with the ISA bus over GPIO pins?
I've brought this idea up as well, and I've been dreaming of OPL3 FPGA sitting on ISA (but OPL3 FPGA is already done). There has never been much interest. Basically, an FPGA sitting on ISA bus could be anything, any sound card, any video card, or multitude of all those at the same time, or SD card slot that looks like IDE to PC. Given that backpanel has enough space for all connectors that is. It could even upconvert MDA to DVI or whatnot at the same time, and sound output would not be limited to analog but could be digital SPDIF. Imagine the possibilites of also sniffing the bus to make more accurate CPU emulators.
The problem is mainly that the hardware design for a single ISA card with FPGA is not easy. You have to level convert between 5V TTL signals on ISA and 3.3V signals on FPGA, and large enough FPGAs tend to be in huge BGA packages not soldered on by a hobbyists for prototyping any more. It can be done with an array of discrete logic chips, or maybe a CPLD that is also a programmable logic chip. It just needs a ton of FPGA IO pins just to connect to ISA bus.
I'm not that familiar with writing VHDL or other hardware description language but I've been toying around with this idea. As there are a lot of FPGA hobbyist boards, a simple solution might be a ISA board that has the voltage level conversion and then has a header for connecting an existing FPGA module such as as Saanlima Pipistrello or Zybo.
So those are the reasons that it's much easier to just write the whole PC to run inside the FPGA, as you don't need much external hardware.
Midi uart is also very simple to do with FPGA, no need to have external hardware for that.