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Comment by jamespo | Hacker News Reader

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

In latency and power usage, yes. In compatibility and accuracy, no. Both are Turing complete, so there's nothing you can do with one that you can't do with the other.

If you take the SNES core, my software emulator has 100% compatibility and no known bugs, and synchronizes all components at the raw clock cycle level. It also mitigates most of the latency concern through a technique known as run-ahead. But it does require more power to do this.

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.

Lower latency is definitely a thing. With FPGA it's possible to 'chase the beam' like the original hardware, and have much reduced input latency from devices, etc. With an emulator you're going to be fighting the OS and the frameworks you built on top of. Even if you go "bare metal" (like my friend's BMC64 project which runs a C64 emulator like a unikernel on the RPi with no OS) you are still dealing with hardware built for usage patterns very different from the classic systems. You're always going to be one or more frames behind.

That is true. There are however techniques software emulators can use like run-ahead that can get you lower latency than even the original hardware on a PC: https://near.sh/articles/input/run-ahead

The caveat is that it doesn't always work, and it makes the power requirements even more unbalanced. Some might also see it as a form of cheating to go below the original game's latency. If you want to match the original game's latency precisely, FPGAs are the way to go right now for sure.

Run-ahead seems pretty cool, great technical write up. How would you compare this to the feature called frame-skipping that I often see implemented in software emulators?

Frame-skipping is just a speed hack of skipping rendering every other frame or so, and makes games very unenjoyable to play. It won't help with input lag at all.

Agreed about chasing the beam. With a SNAC addon and a CRT TV, you can even hook up original light guns to the mister and they work prefect.

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"

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