PCI-e 2.0 card in a PCI-e 1.0a Slot... Max Speed?

[cwiz]

I have a HD 3850 in my older MSI K8N Neo4-F motherboard with an amd x2 3800+ and 2gb of ddr 400 ram and a ~600w psu with a beefy 12V rail so i'm not worried about being short on power... i'll repost when i get home with actual numbers

It kinda sucks compared to the super-clocked 7900GT I had in there before it fried Volt mods are fun but they dont last for ever!

According to wikipedia, most PCI-e 2.0 cards are compatable with older PCI-e 1.0 slots. This is good news for me, but the catch is that the newer card can't run any faster than the 250 MB/s data rate and 2.5 GT/s transfer rate (max speed for pci-e 1.0)

So my question is, how do I know when a newer card will be maxing out the speed of my old PCI-e 1.0a x16 slot?

I want to keep the cost under $150 so I've been looking at the GTS 250 and HD 4850. Any idea what rates these cards run at? Can I go for a better card?

 

[Yami]

An HD4850 won't be impeded by the lower transfer rate - neither will a GTS250. Only recently have cards started to saturate even 1.0.

 

[Baez]

The number of lanes is more important than the PCI-e version for now. A GTX 480 running in a PCI-e x16 slot but in x4 mode is not a good mix.

 

[cwiz]

why would my pci-e 1.0 x16 be running in 4x mode? isn't it default running at 16x?

 

[Yami]

He's not saying yours would, it's just one of the main considerations now.

For example, the P55 chipset (for i5 and i3 processors) has two PCI-E x16 slots - however there are only 16 'lanes' to the CPU so if you have multiple video cards then they both have to run at x8 speed (half).