3 ms·

> your only goal is running all known software, then you can get away with some massive accuracy bugs. > Some people want to do retro programming and develop

> your only goal is running all known software, then you can get away with some massive accuracy bugs. > Some people want to do retro programming and develop new software for a platform. And if you don't have accurate emulation, then the more likely you are to introduce a bug that works in the emulator but not on real hardware. The two things go hand by hand. If era-developed software is unlikely to suffer from timing bugs, then _your own software_ is also unlikely to suffer from timing bugs. It's down to the same argument. It's like claiming that because I developed for Pentium 4, my software is unlikely to work on the Pentium 3. Save for the very explicit case that I use some new extensions, how crazily out of the way would I need to go in order to even remotely hit such an issue? In fact, it can all be summarized to: what CPU timing would you even emulate ? Why would you even target the P3 _specifically_? Why not Transmeta? Note that this does not apply to accuracy emulation of accompanying hardware, but then again I would also claim that accuracy of hardware emulation is hardly relevant post-P3, since _the real hardware_ often is massively inaccurate by any definition of the word. Why accurately model a specific Radeon card, when the budget model of the same year is completely different , with the differences abstracted by hacks in the driver ?

phire 5y ago
Accurate timing is most useful when you are retro-programming a video game, or something else real time. How do you know if your game will run at 60 fps if the execution times aren't accurate? > what CPU timing would you even emulate Ideally your emulator would support as many CPU + hardware configurations as possible, at many different speeds, so you can test as many as you want. But just one single accurate hardware configuration is better than none. At least then I can say "I programmed this game it runs on a Pentium III 550E, with a Riva TNT2" It's exactly the same when doing retro-programming on real hardware. If you only have one PC, then you can only confirm it's working on that exact same hardware configuration. But accurate emulators have advantages due to cost and ability to easily support multiple configurations.
- AshamedCaptain 5y ago
  > How do you know if your game will run at 60 fps if the execution times aren't accurate? Again, this is not a console. If you rely on a specific Pentium 3's instruction timings to reach 60 fps, your game is not going to reach 60fps _on any other PC_, not even if someone has an identical CPU, since any single other difference in hardware, configuration, or even layout of the filesystem is going to matter much more. You just can't get away with the same kinds of bug you can get away with in consoles, because even just trying ATI vs NVIDIA (or any two different brands of accelerator) is already going to be a completely different environment and timings, likely enough to trigger all those bugs (or at least more than different instruction timings will). i.e. even the simplest of emulators (incl. a virtualizer) with a runtime cap is going to suffice for the usecase of mildly estimating a framerate based on the CPU of some era. And there's very little value to increase the accuracy of such estimation since with so wildly varying PC hardware anything you can produce is going to be irrelevant anyway. (How to make a similar accurate-enough estimation of GPU performance is a different story).
  - memetomancer 5y ago
    There is a world of difference between your inability to see the appeal/utility of a thing and that thing being actually worthless, as you are so stridently insisting here. For a mental exercise, just to prove it to yourself, why don't _you_ try examining all the reasons such accurate emulation might be desirable? The other poster already provided a reasonable motivation - preservation. But since this discussion started, you've only really come out swinging with disparagement. One has to wonder why you are putting so much energy into suppressing and trashing someone's hobby. Frankly it looks to me like you have some kind of preconceived and inflexible bias, or that you maybe trying to discover the appeal to this effort in a pointlessly adversarial way. Not a great look. If you really want people to think you have a smart, winning argument maybe try to show some understanding of both sides of the coin before floating your attempt at a clever and withering denouncement.
    - nitrogen 5y ago
      To add an example to your arguments, the C64 and PC/XT demo scenes show what can be done with cycle accurate retrocomputing. Especially 8088mph: https://youtu.be/yHXx3orN35Y https://youtu.be/yHXx3orN35Y

phire 5y ago

Accurate timing is most useful when you are retro-programming a video game, or something else real time. How do you know if your game will run at 60 fps if the execution times aren't accurate? > what CPU timing would you even emulate Ideally your emulator would support as many CPU + hardware configurations as possible, at many different speeds, so you can test as many as you want. But just one single accurate hardware configuration is better than none. At least then I can say "I programmed this game it runs on a Pentium III 550E, with a Riva TNT2" It's exactly the same when doing retro-programming on real hardware. If you only have one PC, then you can only confirm it's working on that exact same hardware configuration. But accurate emulators have advantages due to cost and ability to easily support multiple configurations.

AshamedCaptain 5y ago
> How do you know if your game will run at 60 fps if the execution times aren't accurate? Again, this is not a console. If you rely on a specific Pentium 3's instruction timings to reach 60 fps, your game is not going to reach 60fps _on any other PC_, not even if someone has an identical CPU, since any single other difference in hardware, configuration, or even layout of the filesystem is going to matter much more. You just can't get away with the same kinds of bug you can get away with in consoles, because even just trying ATI vs NVIDIA (or any two different brands of accelerator) is already going to be a completely different environment and timings, likely enough to trigger all those bugs (or at least more than different instruction timings will). i.e. even the simplest of emulators (incl. a virtualizer) with a runtime cap is going to suffice for the usecase of mildly estimating a framerate based on the CPU of some era. And there's very little value to increase the accuracy of such estimation since with so wildly varying PC hardware anything you can produce is going to be irrelevant anyway. (How to make a similar accurate-enough estimation of GPU performance is a different story).
- memetomancer 5y ago
  There is a world of difference between your inability to see the appeal/utility of a thing and that thing being actually worthless, as you are so stridently insisting here. For a mental exercise, just to prove it to yourself, why don't _you_ try examining all the reasons such accurate emulation might be desirable? The other poster already provided a reasonable motivation - preservation. But since this discussion started, you've only really come out swinging with disparagement. One has to wonder why you are putting so much energy into suppressing and trashing someone's hobby. Frankly it looks to me like you have some kind of preconceived and inflexible bias, or that you maybe trying to discover the appeal to this effort in a pointlessly adversarial way. Not a great look. If you really want people to think you have a smart, winning argument maybe try to show some understanding of both sides of the coin before floating your attempt at a clever and withering denouncement.
  - nitrogen 5y ago
    To add an example to your arguments, the C64 and PC/XT demo scenes show what can be done with cycle accurate retrocomputing. Especially 8088mph: https://youtu.be/yHXx3orN35Y https://youtu.be/yHXx3orN35Y