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SSE instructions in DOS programs? (Developers)

posted by RayeR(R) Homepage, CZ, 03.01.2019, 14:32

I guess that SSE should work without setting those 2 bits in CR4 - if you don't need turn on exceptions (code should work without them too). I'm not sure what exactly bit 9 does. FXSAVE instruction save FPU, MMX, SSE regs. context to given location in memory. But as I told for a single task OS it's not necessary if no other code will use this regs. Here is better description with some sample code
they even set some bits in CR0.
In order to allow SSE instructions to be executed without generating a #UD, we need to alter the CR0 and CR4 registers.
I don't know what they means by "#UD" but from this description it seems that bits must be enabled to allow SSE instructions even on single task OS. But you told it didn't crash. I'm confused...

DOS gives me freedom to unlimited HW access.


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