I am slowly building a server for my digitalized music and movie collection. I have a Super Micro X7SPA-HF-D525 and am thinking about bringing a graphics card into the mix. Reason is I want something that can play my MKV files in 720p and 1080p flawlessly, and am therefor thinking instead of building a separate machine for that, then why not turn my high-end NAS into at least a low-end HTPC... The MB have a x16 slot running at x4 speed - what would happen if I wanted to use a normal PCI Express 2.0 x16 card in this 1.1 x4 slot? Would it be any good for decoding 1080p video?
You'd loose a fair bit of performance there, dependant on the card, but any reasonable GPU should be capable of 1080 MKV without grinding to a halt.
With HD5870, you were losing about 25% of performance for PCI-E 2.0 x1 (=1.1 x2) versus PCI-E 2.0 x16 : http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/25.html
Im thinking of a Radeon 5450, wich is made for x16 gen 2.0 - put I only have a x16 running x4 gen 1.1... Is that ok?
5450 isn't a higher-end part so shouldn't really be affected much at all. Even a fast card like the 5870/6870 seem to lose around 10% at most. Since it's not a big expense why not try it out? Certainly should have no problem playing 1080 MKV as said, even a pretty modest CPU can cope with that on its own.
There are PCI-E x1 HD5450's. Do your math . But i am not sure HD5450 is the best choice for HD video, even HD5570 is not the "perfect HTPC card" : http://www.anandtech.com/show/2935/3
