Console and software emulation: does perfection exist?

Well I don't know what you looked at ... There is STeem, there is CaSTaway (which I use on the PSP, where I still use it occasionally to play Jimmy White Whirlwind Snooker, Gods, Xenon 2, and the likes) ... in my experience, STeem is the best one on PC.

As for problems with some demos, that is of course possible. I have no idea though when you last looked at it?

 

IMHO we wont see cycle-accurate emulators for anything released since 1990. So far I seen no emus that even tries to emulate caches. Seeing how much time was spent for accurate emulation of the m68000 prefetch alone makes me confident that all emulation for newer CPUs will only be "good enough" and not perfect.

 

Game Boy Color? GBA? None of them have caches

Though of course you're right in concept, though drawing the line through a year isn't necessarily very smart...

 

Err... they dont have caches???????

 

No, they don't.

I hope you were using irony

 

I wasnt . Im still not entirely convinced, dint find documents for GBA that clearly state either way. Since the early 90s caches got cheap enough to add that there really is no reason not to use one. But you understood what I meant to say anyway

 

By the way, I do know that one trick at any rate works fine - the trick where they use the vertical scan rate to change the palette of a single color to create more than the 16 colors on screen that you are normally limited to. That works great, among others in Gods where it creates a wonderful background sky that is not present in most other versions (i.e. SNES, PC). This is also used in many intros. Most of the Atari Game disk compilations start with demos/loaders that use this trick and they all seem to work perfectly.

 

The big issue is the trick used to open the right and left borders, which is then used to do hardware scrolling. It requires multiple clock cycle accurate writes to the video hardware, at a specific point in a scan line, though my guess is that you could identify the most common variations without cycle accurate emulation.

 

Last time I tried Steem everything seemed to work - including most of the noborder demos - It seemed pretty solid, and ran some old code of mine that did 50fps fullscreen vertical scrolling using one of the hacks.
Atari VCS emulation seems pretty solid now though

 

Caches are mostly useful when the memory can't keep up with the CPU, as in all modern systems. Caches then prevent the CPU from stalling waiting for memory at every memory access, it only has to stall when fetching new cachelines from memory into the cache. (Well, this is a very simplified explanation, but good enough for the purposes of this post).

At the low clock frequences of the GBA, and especially the GBC/GB, even the cheapest simplest memory can easily keep up.

 

Just tried it and it's not bad but the unpatched cuddly demo has messed up horizontal scrolling.
I should find a copy of the ULM demos, some of those groups used mechanisms to shorten scan lines as well. To waste less scanlines at the top in the scroll routine.

 

Maybe it was SainT that ran better - try it at http://leonard.oxg.free.fr/

I only ever used the combination of noleft border / noright border to set the screen base to a multiple of 160 bytes - just to allow vertical scrolling to work well.. Given the hassle of converting an amiga game I didnt want any extra memory to fill

( I'm going to have to unpack my backup CD of ST stuff now... damm corrupt HDDs )

 

Ahh the Atari ST. I didn't own one myself but a friend of mine did and I was always impressed by the quality of some of the demos available on it considering it didn't have a blitter etc.

The carebears (I think they were called. norwegians?)did some amazing stuff. I never managed to figure out how a machine with such small base resolution (320*200 I think) and just a 68000 could use the entire screen for graphics and have stuff flying around all over.

Oh the memories. Some things WERE better back in the old days!

Today I curse over how IE7 can ramp 3GHz CPU load through the roof just by having the mouse swirl around over a bunch of hypertext links.

They sure don't code like they used to..

Peace.