Earlier quoted context omitted.
Typical desktop GPU ram does not support being write-back cached by the CPU. With PCIe resizable BAR, you could map the area into ram, so you could technically fit 32GB to memory, but it would have to be uncached (or write-combine cached), which would make it really, really slow. There are a bunch of datacenter GPUs that support full cache coherency, but if you used them like that the VRAM would be very high latency…
Isn't the problem with write back cache mode just due to the GPU being unable to invalidate cache lines in the CPU?
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