MiSTer FPGA Forum

Hi. You've probably heard that demos are quite picky to hardware, as far as they usually go to the edge and farther of what platform is capable of. It's kind of common that not even every emulator can run demos perfectly, they should be cycle accurate or more.

What about PSX core? Have anyone tried PSX demos? I did a little effort, trying to run some random demos. Most of them do not run at all, probably because of wrong image format (just show BIOS instead). Tajmiing demo shown me this:

That's no surprise it doesn't work:

First the timing. The demo is created by Amidog.
While being a good developer that has written a nice CPU and GTE test, they always aimed for doing more excentric things.
In this case it tests for the video timing being super accurate. In fact so accurate that a NTSC PSX also cannot run the original demo, only PAL, because of the slightly wrong clock crystal.

Second the method. It manipulated the display registers only, so in fact it does beam racing only.
So even if this could work on Mister, it could only work via VGA out, as the scaler cannot handle all the on-the-fly changes to resolution and hsync/vsync

An interesting topic for preservation, anyways.

nymous wrote: ↑Tue May 09, 2023 2:04 pm

Have anyone tried PSX demos? I did a little effort, trying to run some random demos. Most of them do not run at all, probably because of wrong image format (just show BIOS instead).

Off the top of my head, at least Dekadence's Mad Situations (2023) and Desire's RUN CRASH! (2021) and Paradox & Threepixels' Deadline Caught Me (2001) all run fine on the PSX core.

IIRC RUN CRASH! shows some garbage on the right-hand side of the screen on a digital display, but since the demo was probably intended to be viewed on a CRT where it'd be overscanned out, it's not an issue with the core per se.

I thought when OP said about demos it was those demos from psx magazines back in the day.

Running demos for platforms like C64 and OCS Amiga works really well, them being relatively small and well-known targets. Being an FPGA doesn't magically make a more accurate core. The PSX core is a work of art as it stands for even fitting on the board at all running as well as it does.