Will a Radeon HD 6570 PCIe 2.1 card function plugged into a Dimension 9100 0x8582 motherboard with a PCI2 1.0 slot.
Or does there need to be a firmware upgrade.
There's a good chance it will work. I have a 6570 in a circa-2007 mainboard, and all functionality is present, including S3 sleep.
I noticed troubles with the 5XXX series when I tested some, but the 6XXX cards I've tried (from several vendors) have all worked without issue.
There would be no firmware upgrade only a bios update that would support PCIe 2.1 on this older motherboard. However, since there has not been a bios release since 2006 it is unlikely. It has been shown to be a gamble whether it will work or not on an older 1.0 board. Therefore, I recommend either an older ATI 2.0 card or an Nvidia card because they are all 2.0. With today's cards, the only one close in performance is the Nvidia GT 440. Otherwise, look for older cards like the 9800 GT or you could try the newer GTS 450 which should work on your 375 watt power supply. It just depends on what you want the upgrade for. If it's for gaming, I would consider the GTS 450 because the older 9800 GT is just harder to find now.
thanks for your input.