That video card is not suitable for Premiere Pro.
What processor do you have?
this reminds me of the hd bug where it won't use more than 4 cores unless its output is higher than hd.
"2) However, there is a definite limit as to how may CPU threads will get utilized for a HD to HD H.264 output workflow"
Hmmm, I'm using Windows Media format for my outputs with preset HD 1080p 24 as they're most widely available. I've not tried rendering at H.264 but I'll give that a try for the purposes of this conversation.
As Peru Bob stated, that GT 630 is unsuitable for Premiere Pro. There were/are two versions – both of which range from abysmal to bad. One had only 96 CUDA cores (the same Fermi-based GF108/117 GPU as its GT 530 predecessor); the other, 384 CUDA cores (a newer Kepler GK208-based GPU that's restricted by its 64-bit memory bandwidth). Both of those, unfortunately, are equipped with extremely lousy DDR3 VRAM with an extremely low throughput of less than 30 GB/second! And when I tested a GK208-based GT 730 with GDDR5 VRAM (40 GB/second throughput), normal applications began to slow down noticeably compared to using a higher-end GPU or even integrated CPU-based graphics.
By the way, that E3-1270 requires a discrete GPU since it lacks an IGP. Unfortunately, the power supply restricts the GPU that you may use. With that CPU and your existing PSU you may be able to get away with a reference-clocked GeForce GTX 1050 Ti in your system. Heck, even the newly-introduced GeForce GT 1030 (newer Pascal architecture using the GP108 GPU, 384 CUDA cores, 64-bit GDDR5 VRAM with a throughput of 48 GB/second) would be a significant improvement over that GT 630.
Thanks all for the replies and the technical details particularly.
Because of the type of motherboard and power supply my options for a gfx add on card were limited and my card gets me dual screen which was the main reason. Handles any games I play fine but that's increasingly infrequent!
With my next machine when the time comes I'll look at the hardware requirements and recommended cards by Adobe and factor that into my purchase.
In the meantime it does the job and I can leave it to render during the night if required.
Thanks again for the replies and I wish you all a great week ahead!