Uncacheable speculative write combining

USCW stands for Uncacheable Speculative Write Combining. It is a computer BIOS setting for memory communication between CPU and graphics card. It allows for faster communication than the Un-Cachable setting, as long as the graphics card supports write-combining, which most or all modern graphics cards do.

What the write-combining does is instead of writing single bits, data is temporarily stored in write combine buffers and released in burst mode.