I have a pentium D 820 in my Dell. I cannot get a 100% crystal clear answer from Dell about what processors the Bios will support (I have been made to understand that just because the 945 chipset supports a certain processor, it does not necessarily mean my mobo will... this was the first and last time I buy a pre-configured system).

Anyway, does anyone have an opinion on what kind of performance increase I might see from dropping a pentium D 9xx in there? Will the smaller chip and the extra cache make much of a difference, let alone a bit extra core speed?

The system currently has a 4870xt and 4gb of ram in there (running at only 533). I know that's heavily lopsided, but x2 was a (sweet-ass) gift and the memory was too cheap to just get 1 gig (I already had 2 installed). I know that it is simply way too much video card for the mobo/CPU, but I'm not ready to build a whole new system around it just yet. I have seen the higher pentium D's for around $100, and if it will make a notable difference, I am willing to do that.

Thanks in advance for any advice =)

I don't think it's worth it to buy another Pentium D. If your motherboard supports it, look into either the 65 or 45nm Core 2 Duos. They offer a large increase in speed and run cooler.

I need to really dig into the bios thing on my mobo -- see if I can support a better processor. Going to try to hit up the Dell boards, but it's hit and miss over there...

You could try cross flashing your motherboard

That MIGHT make it support Core 2 Duos and etc.

No guarantees...

the 945 chipset supports all 65nm core 2s i believe. I don't' think your motherboard gets a say in your chipsets decision on its preference of silicon.