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Show HN: Game Bub – open-source FPGA retro emulation handheld

eli.lipsitz.net

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Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#51

Post by kbrackbill »

This is really cool, thanks for the writeup. Love how thorough you were, one of my first thoughts was whether you could hook it up to a gamecube and it was already done in the blog post :).

One cool advantage of real cartridge compatibility I hadn't really thought about is that lets you not have to think about memory mappers (I'm mostly familiar with NES's dozens of different mappers, not sure if GB carts work the same way) and other custom cartridge hardware since you're just "emulating" up to the cartridge boundary. I guess this means even crazier hardware like the camera/rumble/sewing machine would "just work" with an original cartridge without any special support right?

I guess that doesn't save too much for this though if it supports loading ROMs. For that do you still end up having to emulate all the different mappers in the FPGA?

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#54

Post by alexjplant »

ecshafer wrote: post #10

I don't really know if this is a stupid idea or not, I don't really have hardware experience. But the older systems, say NES, SNES, Genesis etc are pretty simple systems. Patents also have a lifetime. Why aren't we getting recreations of the hardware via a SOC sold that near-perfectly emulates the system? The FPGA projects are as close as I see this happening, but FPGAs are pretty expensive I imagine compared to some…

As I understand it this has already been done for several systems. The first time I saw such a device it was one of those bootleg "100 Games In A Joystick" things that Ben Heck tore apart because it contained a glop-top "NES on a chip".

> FPGAs are pretty expensive I imagine compared to some 40 year old cpu design and 1kb of ram.

The MiSTER Pi set me back $180 and is perhaps my favorite purchase of 2024. It'll run almost any system made before the year 2000 and the gap is rapidly closing for lesser-appreciated consoles like the Saturn and Jaguar. This represents a tremendous value; it's hard to argue with that kind of money for an entire century of gaming. I heartily recommend picking one up.

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#55

Post by elipsitz »

kbrackbill wrote: post #51

This is really cool, thanks for the writeup. Love how thorough you were, one of my first thoughts was whether you could hook it up to a gamecube and it was already done in the blog post :). One cool advantage of real cartridge compatibility I hadn't really thought about is that lets you not have to think about memory mappers (I'm mostly familiar with NES's dozens of different mappers, not sure if GB carts work the sa…

Thanks! Yeah, support for physical cartridges makes it a complete non-issue.

Mappers are a huge problem with the NES, but a much smaller problem with the Game Boy. There are only a few official ones (6 iirc), and one or two unofficial ones. And unlike the NES, the ROM includes a cartridge header that tells you which mapped chip is used.

For the GBA, there aren’t any mappers (except for one or two GBA video cartridges). There’s some extra hardware (like rumble or gyroscope), but not a whole lot. So yeah, I have to emulate all of those but it’s not much of a problem.

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#57

Post by christkv »

LeoPanthera wrote: post #31

I have an Analogue Pocket, which works really well, but the fact that it uses an FPGA is essentially meaningless to me. Is there really any significant difference compared to software emulation? I know how they're different, I understand the mechanics of it, I just don't understand why it's not possible to make a software emulation that is as good as FPGA emulation. Or maybe it is possible. I always felt like doing i…

Mostly input latency since it does not incur all the layers of latency in the os plus the emulator.

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#58

Post by christkv »

goosedragons wrote: post #28
ecshafer wrote: post #10

I don't really know if this is a stupid idea or not, I don't really have hardware experience. But the older systems, say NES, SNES, Genesis etc are pretty simple systems. Patents also have a lifetime. Why aren't we getting recreations of the hardware via a SOC sold that near-perfectly emulates the system? The FPGA projects are as close as I see this happening, but FPGAs are pretty expensive I imagine compared to some…

We do, sort of. There are ASIC based clones of the NES, SNES, Genesis, GBA and GBC. Hyperkin for example sells a few, the SupaRetron HD is an ASIC based SNES clone, the MegaRetron HD is an ASIC based Genesis clone. Some Chinese companies have Game Boy Clones (e.g., GB Boy Colour). They aren't perfect because they aren't perfect 1:1 reverse engineered chips and nobody seems willing to spend the money to fix all the bu…

There technically is also a path from FPGA to ASIC so you could use a FPGA for dev and test and at some point if it makes sense make a volume product based on that FPGA.

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#59

Post by dailykoder »

pipes wrote: post #42
elipsitz wrote: post #32

Earlier quoted context omitted.

I agree, and wrote a rant about this as part of the post: https://eli.lipsitz.net/posts/introducing-gamebub/#a-brief-r... IMO: the only real advantage is that it allows you to meet the precise timing needed to interface with physical hardware, like cartridges and other consoles (with link cables). I think they're also really fun to write, because you think more like a hardware designer than a software engineer.

Am I correct in thinking that FPGAs have an advantage over software emulators when it comes to latency? In particular the latency from the host operating system before input has even been received by the software emulator? I.e. FPGAs don't have a host OS and will have the same latency as original hardware? This is very much a genuine question, I just want to know if my intuition about this is right or wrong. Your pro…

FPGAs not only have no host OS, but they are actual hardware. The only thing you program are lookup tables which then represent logic gates/multiplexers which only have the normal hardware latency. There is literally no software involved in execution.

That's why you can build "any" hardware with them. Even CPUs which then execute your desired software

Re: Show HN: Game Bub – open-source FPGA retro emulation handheld

#60

Post by hoc »

What a great writeup. I am always interested in these specifics of current design decisions even if I am so not into gaming handhelds. But the questions around display, enclosure, battery power and connectivity and the chose. borders between circuit and software are always current and shifting with time and goals. I love the Pico W integration, which is still one of rather undervalued development items of the last few years.

Great work. Thanks a lot for sharing.

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