Well, the answers as I see it to your question :
1) Memory bandwidth : The PCChips mobo is using a very odd chipset. Remember how VIA motherboards used to have lower memory performance (still do, a little bit, but not nearly as bad as before) than the Intel chipsets? Well, I totally suspect that's what you're seeing. Even including that, your bandwidth numbers are totally sucky. I don't know. Try reinstalling all drivers for the motherboard, Also, another BIG contributor is #2 below
2) It's totally crucial that your video is integrated. Usually an integrated video card shares memory with the system, which means that displaying anything on screen uses system memory bandwidth. You really notice this in a game like Q3, where your video card sucks up all the bandwidth it can get -- in your case, the video starves the CPU and vice versa. I don't know why the Voodoo3 doesn't improve the situation, but it should...