alexanrs wrote:Don't you have a motherboard with a PCIe slot? Getting flash acceleration with AGP cards might be impossible (I don't know if the bridged ATI cards have it)
I can confirm Flash/h.264 support does work on bridged ATi cards, at least with newer ATi AGP Hotfix drivers - I have an HIS HD 4350 AGP 512MB (which are apparently still made; Newegg and other retailers still sell them brand new) in my P4EE, and it handles 1080p YouTube without breaking much of a sweat. The in-the-box drivers from HIS do not support Flash, but the latest AGP hotfix from AMD enables it. There is still a CPU component for Flash, which is "heavier" for a P4 or other old CPU as opposed to something like a Core i7, but from my my own observation its like 20-25% CPU load + GPU, versus like a few % CPU load on a modern system GPU, or 100% CPU load (and it still stutters) for Flash-on-CPU with the P4. This is at 1080p mind you. Drop things off to 480p or 720p and its much less of an issue (and personally I prefer lower-resolution streams a lot of the time as they eat up less of my Internet bandwidth).
For PCIe, you'd want to go GeForce 8400/8500/8600 or 9 series (including the G92 8800s) or higher, or Radeon HD 4000 series or higher. AFAIK there are no other AGP cards than the bridged HD 4000 that support Flash, but a few of the lesser Radeon cards will also support h.264 (e.g. X1600Pro AGP will still provide AVIVO h.264 support, which could help with Blu-ray, and will ofc still support DVD playback). I don't know much about the PCI GeForce 8/200/600 cards - technically the GPUs support CUDA, Flash, etc but I'm not sure if the PCI bridged cards implement it (I know at least on the GeForce 6, the bridged cards gave up a lot of video decode features).
Putting the GTX 960 into a 939 motherboard *should* work, but it may refuse to boot. I know that when I tried GTX 770 with my DX48BT2 it locked the machine up on power-on, and some searching revealed there is apparently an incompatibility between the GTX 770 (and ostensibly other newer cards) and some pre-PCIe 3.0 boards (of course, that isn't 100% - there are plenty of people with GTX 770 in PCIe 2.0 boards). I would say try it and if it works great, and if not at least you'll know. A GeForce 8600 shouldn't cost too much, and will give you Flash, 264, partial VC-1, etc support as well as relatively up-to-date drivers for Vista/7 (and afaik 8/8.1 too).
WRT SSE3 - it may or may not help. My P4EE (which is SSE2) doesn't seem to have much trouble; it isn't a rocket-ship, but it still does a good enough job. You shouldn't give up SSE2 support though - that will break many applications.
RAM-wise, you want at least 2GB. 4GB is better. Enabling ReadyBoost can also help with some things.