Gamesindustry.biz seems to think backwards compatibility is out of the question for the Xbox2, but how hard would it be for the next-gen ATI GPU in that machine to emulate the geforce 3+ in the Xbox? I think that if it weren't impossible, and could run well, a harddrive add-on (since Xbox2 is also rumored not to have one of those) with an emulator to play Xbox games on the unit would be a good product for MS to put out there. I know I'd buy one.
A question about emulation
- Thread starter GwymWeepa
- Start date
Not sure if this was mentioned in the other thread, but it'd be quite difficult to emulate a mass storage device if the required space isn't there (no HD in XboxNext)...
On the other hand, if the chipset of Xbox could be successfully emulated, I wouldn't be suprised if Microsoft would just sell the required HD as an add-on for those that want backwards-compatability..
On the other hand, if the chipset of Xbox could be successfully emulated, I wouldn't be suprised if Microsoft would just sell the required HD as an add-on for those that want backwards-compatability..
The NV2A register interface could be emulated in software and then translated to whatever chip is used in nextbox, but getting performance good on such fast components would probably require immense development efforts on MSs behalf.
There is a MAME emulation thread in the games forum where it was revealed simply emulating a 150MHz R3xxx chip requires immense processor performance, and a 733MHz celeron wouldn't exactly be easier.
There is a MAME emulation thread in the games forum where it was revealed simply emulating a 150MHz R3xxx chip requires immense processor performance, and a 733MHz celeron wouldn't exactly be easier.
Guden Oden said:
The problem is you can only realistically do this if your new hardware supports a superset of the old harware (featurewise).
You can certainly emulate omitted features on the vertex side, but emulating low level raterization differences is impractical. By this I mean things that occur outside the shader, like Z/W interpolation, destination blending etc etc.
What can the NV2A do that a far more advanced chip with what is likely an even more sophisticated shader model than VS/PS3.0 could not?
Guden Oden said:
Low level they work differently, so emulating the NV2A exactly ain't easy.
If you look at the WRECKLESS GDC paper from last year, you will see that it uses the bit pattern of the W/stencil buffer for depth of field. So any emulation must be bit exact.
Can't this be replicated via pixel shaders, or would it be too slow/impossible using dx9-style shaders? (Assuming nextbox will not have dx10-level capability.)
Guden Oden said:
The simple answer is no.
There is still stuff that occurs that the shader does not control, interpolation and destination blending being the obvious ones. ATI and NVidia just solve the same problems a little differenttly and because consoles expose these low level differences, emulation is probably impractical.
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