The 7850 is quite a bit faster than a 560Ti, not more or less the same. I can guarantee good compatibility with games with the 7850, at least under Windows 7 and Windows 8/8.1. Windows XP is kind of a grey area, both companies have started to really leave it behind with recent driver releases.

I'd just use somewhat older drivers like 13.1 to be as stable and compatible as possible.

Actually, switching to the GTX 560 Ti would probably increase compatibility over what you've got already. My experience between Radeon and nVidia cards is that Radeon is a little more powerful vs. same generation nVidia cards, but less compatible with older software. Some of my friends have lost the ability to play certain indie games by switching from nVidia to Radeon and as such I refuse to ever put a Radeon card into any of my systems because of my interest in older titles and indie titles.

That said, while I'm not sure how much compatibility you'd lose going from the HD4850 to the HD7850, I'm willing to bet you would lose some for older titles. (You would also gain some for newer titles.)

F2bnp wrote:

The 7850 is quite a bit faster than a 560Ti ... I can guarantee good compatibility with games with the 7850, at least under Windows 7

Gemini000 wrote:

Actually, switching to the GTX 560 Ti would probably increase compatibility over what you've got already... Some of my friends have lost the ability to play certain indie games by switching from nVidia to Radeon

Thanks, had crossed my mind to put the gtx560ti in the xp/vista box and the hd7850 in the 7 machine - looks like that might be best.

Indeed, that would be a terrific choice!

nVidia 600 series have XP drivers; I haven't personally tested them, it just showed up in the readmes I've skimmed for my card.

As far as the 4850->7850, you'd move out of the "Catalyst Legacy Driver" package into more current development, so there's a good chance you'd improve support/functionality for DX9 games (ATi/AMD does a wonderful job of abandoning hardware support at the drop of a hat, and not worrying what is left broken); not sure about DirectX 8 and older. When I had HD 4800 cards they were fine with DX8 in WinXP, but under 7 it was non-stop problems. Haven't tested DX8 + Win7 + nVidia 600 yet; it may work better, I noticed my Intel graphics under Win7 seems to be better with DX8 at least (hence I'm guessing it may be driver/hardware related, not entirely Win7 related).