If on one side you have 8 memory banks (16 in total), then it has a x8 configuration. If it's 512MB then it's considered 32x8 = 256. If it's 1024MB, then it's 64x8 (and again, this is for EACH side, not both).
*/Edit*/
Sorry, I misread what you asked. If on your memory module you have 8...