Darxide 32X and 60Hz hardware

[SamIAm]

This is kind of an obscure question, but I'll try to keep it short.

Darxide is a highly rare 32X game released only in Europe. Finding a copy is next to impossible, and if you do get one, you'll need a PAL Mega Drive/32X to play the game because it has regional lockout. However, a while ago, in his infinite kindness and wisdom, ExCyber found a game genie code that would circumvent the protection. This doesn't help with a real copy of Darxide (no 32X GG exists), but it does make the game playable on real hardware with one of tototek's MD-PRO carts. This is what I've got.

Once I started the game, I assumed it was running normally on my 60Hz hardware. Other 32X games going cross-region don't seem to have any timing errors (although not many have been tested). However, I recently had the opportunity to try emulating Darxide (with Gens, obviously) on a computer that could handle full speed 32X emulation. To my surprise, the game ran at a higher frame rate with way less slow-down, in both 50Hz and 60Hz modes.

Can someone explain what's happening here? Why is Gens running the game at the same speed in both PAL and NTSC modes, while my real hardware lags behind? If Gens is going the proper speed, why is a PAL game running slower on 60Hz hardware?

I should note that while the graphics stayed the same in both modes in Gens, the music did change. As one would expect, it was slower at 50Hz. The 60Hz speed was the same as it is on my hardware. Oh yeah, and there are no screen size errors with my console.

Thanks!

 

[Shakey Jake33]

This isn't uncommon, your computer can emulate the polygon games faster than the real hardware can render them. The same happens with PSX games on emulators.

 

[Dyne]

how good is 32x emulation anyway? i remember a while back it wasnt so good. has it improved a lot?

 

[ExCyber]

Why is Gens running the game at the same speed in both PAL and NTSC modes, while my real hardware lags behind?

I suspect, but can't confirm, that Gens is giving Darxide more CPU/memory cycles per frame than the 32X does. This could be caused by not emulating factors that slow down the real CPU (e.g. memory contention), or possibly Gens emulates a fixed number of 32X CPU cycles per frame rather than per second.

If Gens is going the proper speed, why is a PAL game running slower on 60Hz hardware?

The 32X CPUs run at roughly 20MHz, IIRC (not that the specific number is important).

20MHz is 20,000,000 cycles per second.

At 50Hz, that's 20,000,000 / 50 = 400,000 cycles per frame

At 60Hz, it's 20,000,000 / 60 = 333,333 cycles per frame.

So if Darxide pushes the 32X particularly hard, it may be going over the available CPU time. Since it was only released in Europe, the developers might not have added anything to drop frames, and so when a frame goes over the available time it might just be delayed until the next vsync instead of being dropped.

This is, however, just one hypothesis...

 

[SamIAm]

Originally posted by ExCyber@Feb 24, 2004 @ 03:33 PM

This is, however, just one hypothesis...

Cool, thanks for the info. And thanks again for that code in the first place! Unfortunately, this means the only way to really find out whether Darxide is operating normally or not is to do a comparison on genuine hardware at both 50Hz and 60Hz. Not too many people have that equipment AND one of these carts.

Oh well, the game is still playable. It's very good, too, except some things have annoyingly odd collision areas that make them hard to get at. Nonetheless, this is probably the best 32X-exclusive game out there (long live Space Harrier!).