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MiSTer, an open-source FPGA gaming project

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Re: MiSTer, an open-source FPGA gaming project

#21

Post by near »

mbalyuzi wrote: post #20
TillE wrote: post #16

Earlier quoted context omitted.

byuu wrote a good article about this, unfortunately it's no longer available, but basically it should be self-evident that there's nothing inherently more accurate about hardware emulation. If you've actually decapped the original chips and duplicated them exactly in an FPGA, that's pretty cool. But otherwise it's just another approximation. The lower power requirements are nice, of course.

Actually decapping the original chips is very much a thing. See for example Chris Smith's work mapping out the innards of the ZX Spectrum ULA - http://www.zxdesign.info/book/insideULA.shtml .

It is, but these cores are almost exclusively not being done that way. Not yet at least. I hope that they will be, that would be really awesome. I paid $1200 last year for the SNES PPUs to be decapped for this purpose, but it's a truly enormous undertaking to map out those chips and then recreate it in Verilog. You're talking thousands of hours of work per chip. If anyone reading this is able to help with that effort, please do let me know, we could really use the help.

Re: MiSTer, an open-source FPGA gaming project

#22

Post by rtkwe »

Jorge1o1 wrote: post #5

I don’t really know much about game emulation so I was curious about what differentiates this FPGA game project vs traditional CPU emulation. From their github page [1]: >Traditional emulators on CPUs execute code sequentially. This is a tricky method of emulation because real hardware has many chips and all of them work in parallel...This requires a lot of CPU power to emulate even an old and slow retro computer. So…

There was a good article from Arstechnica a decade ago that pointed out why you need so much more power to get perfect emulation. To get exact emulation takes a lot of power because there are a few games which use odd tricks that are hard to document and precisely reimplement in software. FPGA emulation gets around that by more directly emulating the hardware.

https://arstechnica.com/gaming/2011/08/accuracy-takes-power-...

Re: MiSTer, an open-source FPGA gaming project

#23

Post by bcrl »

TillE wrote: post #16
Jorge1o1 wrote: post #5

I don’t really know much about game emulation so I was curious about what differentiates this FPGA game project vs traditional CPU emulation. From their github page [1]: >Traditional emulators on CPUs execute code sequentially. This is a tricky method of emulation because real hardware has many chips and all of them work in parallel...This requires a lot of CPU power to emulate even an old and slow retro computer. So…

byuu wrote a good article about this, unfortunately it's no longer available, but basically it should be self-evident that there's nothing inherently more accurate about hardware emulation. If you've actually decapped the original chips and duplicated them exactly in an FPGA, that's pretty cool. But otherwise it's just another approximation. The lower power requirements are nice, of course.

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.

Re: MiSTer, an open-source FPGA gaming project

#24

Post by tediousdemise »

TillE wrote: post #16
Jorge1o1 wrote: post #5

I don’t really know much about game emulation so I was curious about what differentiates this FPGA game project vs traditional CPU emulation. From their github page [1]: >Traditional emulators on CPUs execute code sequentially. This is a tricky method of emulation because real hardware has many chips and all of them work in parallel...This requires a lot of CPU power to emulate even an old and slow retro computer. So…

byuu wrote a good article about this, unfortunately it's no longer available, but basically it should be self-evident that there's nothing inherently more accurate about hardware emulation. If you've actually decapped the original chips and duplicated them exactly in an FPGA, that's pretty cool. But otherwise it's just another approximation. The lower power requirements are nice, of course.

On FPGAs (depending on the hardware mapping), you get the benefit of lower latency. I consider this to be timing accuracy.

Say you have two implementations of an LED controlled by a switch: one which uses an FPGA and one which uses a microcontroller. The uC implementation must continuously poll peripherals connected to its GPIO pins at a set frequency; it must check the state of the switch, and then change the state of the LED. The FPGA, on the other hand, physically wires the switch to the LED; there is no lag when the state of the switch changes.

The FPGA implementation can be scaled to connect however many additional lights and switches you want (limited by the size of the fabric), with zero overhead lag. This is the parallelization benefit of FPGAs that you may hear about. For the uC implementation, you must add additional switches and lights to the polling loop, which brings down performance in linear time, O(n). This is the drawback of sequential processing.

Re: MiSTer, an open-source FPGA gaming project

#25

Post by zokier »

TillE wrote: post #16
Jorge1o1 wrote: post #5

I don’t really know much about game emulation so I was curious about what differentiates this FPGA game project vs traditional CPU emulation. From their github page [1]: >Traditional emulators on CPUs execute code sequentially. This is a tricky method of emulation because real hardware has many chips and all of them work in parallel...This requires a lot of CPU power to emulate even an old and slow retro computer. So…

byuu wrote a good article about this, unfortunately it's no longer available, but basically it should be self-evident that there's nothing inherently more accurate about hardware emulation. If you've actually decapped the original chips and duplicated them exactly in an FPGA, that's pretty cool. But otherwise it's just another approximation. The lower power requirements are nice, of course.

I think big differentiator is that it is easier to get predictable latencies with FPGA where you control almost everything, compared to general-purpose PC which is not really that well optimized for hard real-time operation. So I believe "race the beam" style things are more easily accomplished with FPGAs, and also having tight audio-video sync. Although the PC emulation scene has been also doing some fairly incredible things too.

Re: MiSTer, an open-source FPGA gaming project

#26

Post by emodendroket »

TillE wrote: post #16
Jorge1o1 wrote: post #5

I don’t really know much about game emulation so I was curious about what differentiates this FPGA game project vs traditional CPU emulation. From their github page [1]: >Traditional emulators on CPUs execute code sequentially. This is a tricky method of emulation because real hardware has many chips and all of them work in parallel...This requires a lot of CPU power to emulate even an old and slow retro computer. So…

byuu wrote a good article about this, unfortunately it's no longer available, but basically it should be self-evident that there's nothing inherently more accurate about hardware emulation. If you've actually decapped the original chips and duplicated them exactly in an FPGA, that's pretty cool. But otherwise it's just another approximation. The lower power requirements are nice, of course.

That's true, but I think it's also true that you could trim a bit more lag if you do it well.

Re: MiSTer, an open-source FPGA gaming project

#27

Post by pomian »

tediousdemise wrote: post #4
GekkePrutser wrote: post #2

This isn't really new, right? I've heard of this years ago. But it is an amazing project. Instead of emulating, they actually rebuilt the old custom ICs (which 8-bit computers were full of) in an FPGA. Really impressive.

Yeah, it really is an amazing application for FPGAs—preserving computing and gaming history. The list of cores available for MiSTer is simply staggering: > Computers - Classic • Acorn Archimedes • Acorn Atom • Alice MC10 • Altair 8800 • Amiga • Amstrad CPC 6128 • Amstrad PCW • ao486 (PC 486) • Apogee • Apple I • Apple II+ • Apple Macintosh Plus • Aquarius • Atari 800XL • Atari ST/STe • BBC Micro B,Master • BK0011M •…

Interesting project would be to dig out some old cassettes from, let's say, commodore 64. Try to load them into a present day computer by patching wires/cables? - and see if they run in this system. I remember writing for example: a mining program, to calculate, overburden, volume and tonnage, at different slopes, different rock types, etc. The science behind the calculations is still valid, but we could likely increase load times, and calculating times.

Re: MiSTer, an open-source FPGA gaming project

#28

Post by emodendroket »

stormbrew wrote: post #19
jamespo wrote: post #13

Earlier quoted context omitted.

So it's not perfect but it's better than emulators...

I'm really curious where you got "better" out of the quoted text. Because it's not there or implied, but people keep reading this into anything about fpga recreations of chips. There's nothing inherently better about doing emulation on an fpga or a cpu, other than basically the amount of electricity involved in doing it. But people keep presuming an improved accuracy that there's no basis for.

Probably the marketing copy for Super NT and similar products... harder to get people to part with hundreds of dollars if your pitch is "lower power draw and reduced input delay"

Re: MiSTer, an open-source FPGA gaming project

#29

Post by zokier »

tediousdemise wrote: post #17
timbit42 wrote: post #9

Earlier quoted context omitted.

I'm still waiting for the KENBAK-1 core.

Is there good documentation or ICDs out there that adequately describe the architecture? Looks like there’s only 50 that were ever made, and only 14 believed to exist today.

http://kenbakkit.com/manuals.html

Seems pretty well documented. Considering the simplicity of the computer, feels like it would be relatively easy project to get to MiST

Re: MiSTer, an open-source FPGA gaming project

#30

Post by mschuster91 »

near wrote: post #6
GekkePrutser wrote: post #2

This isn't really new, right? I've heard of this years ago. But it is an amazing project. Instead of emulating, they actually rebuilt the old custom ICs (which 8-bit computers were full of) in an FPGA. Really impressive.

It is indeed an amazing project, especially its open source nature. It provides some impressive power savings and latency reductions that are very hard to match with general purpose CPUs. But in most cases, it is emulation, as the lead developer will attest. https://github.com/MiSTer-devel/Main_MiSTer/wiki/Why-FPGA "From my point of view, if the FPGA code is based on the circuitry of real hardware (along with the usu…

> It's also not a total solution: by taking many more transistors to programmatically simulate just one, it limits the maximum scale and frequency of what it can support. N64/PS1/Saturn has not yet been fully supported and is still theoretical, but likely, to be possible. Going beyond that is not possible at this time.

The limiting factor here is the amount of stuff you can throw into a single FPGA, correct?

So in theory, shouldn't it be possible to tie a bunch of FPGAs together, with two beefy ones being responsible for replicating CPU / GPU functionality, a couple smaller ones for sound and other "helper" processors, and some bog-standard ARM SoC to provide the bitstreams to the FPGAs and emulate storage (game cartridges, save cards) and input elements (mainly "modern" controllers)?

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