Xbox 2 - The Price of Compatibility?

Randy Lastimosa writes "1UP.com has an interesting article about the next Xbox, and whether it will support current Xbox games. They talked to a number of sources and got conflicting reports. For example, the CEO of Nvidia, who provided graphics chips for the current Xbox, said: 'It's virtually impossible on many levels,' he adds. 'On an intellectual-property level. On practical levels, too.'"

Comments

Re:...On an intellectual-property level...

[Mechanik]

'On an intellectual-property level' What does this mean? It's a computer, they can't port the games?

Well, if you think about it, most of the games won't be just writing to DirectX/Direct3D only. Most or all of the pretty engines are going to be writing (for example) shader code directly for the Nvidia GPU that is built in to the XBOX.

Since we know that XBOX++ will not contain an Nvidia GPU (they're going with ATI instead), it is pretty safe to say that using binaries compiled for the current XBOX will not work. If they did, then that would mean that the graphics chips would have to be functionally identical (or at least close enough) to the Nvidia part. Nvidia probably holds a bunch of patents surrounding the chip which currently preclude this unless MS and/or ATI wants to get sued to oblivion.


Mechanik

Re:I don't get this mentality

[brandorf]

I just thought that I'd clear up the common misconception that there is a performance or innovation cost for including the PS2's backward compatibility. There wasn't. The PS2 contains the entirety of the PSOne hardware, PSOne games are played natively, not emulated, and the PSOne hardware controls I/O when a PS2 game is running. Because Sony already had chip fabs and such for the PSOne chips, repurposing those chips in the new system actyally saved them money. Being able to play the old games was just a benefit of this route.

Speaking as a Xbox developer

[Ryu2]

It'd say it's actually easier on the Xbox to achieve compatibility via software emu than other consoles, because Microsoft stipulates, as a condition to get a game certified by them, all Xbox games must access the hardware the DirectX APIs and XTL libs, rather than writing direct to hardware registers/ports.

The only area where I can see problems is that Xbox vertex and pixel shaders can be (and often are) compiled to nVidia's proprietary binary format (which represents a much more hardware-specific mapping than the standard DirectX hardware-agnostic binary token format). If this issue is solved, or nVidia turns a blind eye, there should be no major technical obstacles to software emulation. Legally, I think it may be OK, as the specifics of the nVidia shader format is not disclosed even in the Xbox SDK itself, so Microsoft could very well write a layer that just translates the nVidia format to whatever internal scheme ATI's silicon will use.

Other consoles, like PS2 allow much more low-level access, so compatibility via software emulation only is more of a pain.