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I think it's safe to assume we are all missing something here.
Originally posted by drbaltazarLet's recap :window 8.1:Direct memory access?not supported anymore ,reason?security!Direct cache access ?same.MSI/x use lapic (already MSI was very latency prone vs IRQ,Invariant tsc was not used properly till some on the web found out everything performed better if itsc was on still not properly used by os or whatever you can come up withIts like ms intentionally slow down window 8 to make window 10 dx12 look fast.
I think your confused.
Direct Memory Access (DMA) is still used in Windows 8.1
This allows devices like your hard drive to place data directly into RAM bypassing the CPU. It has not been disabled, and it works at the driver level.
It's true that programmers cannot directly access RAM any longer - for security reasons, but not in all Applications (i.e. items run in Compatibility Mode can still access, provided they get Administrator permission). But that doesn't mean that Windows doesn't use the same mechanism to access RAM as it did before - it's just now you need to go through a protected Windows API to do it - and all that API does is obscure the actual memory location to your program, it doesn't really do anything else.