Messages in this thread | | | Date | Mon, 29 Jun 1998 00:12:07 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: MMX emulator ? |
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On Sun, 28 Jun 1998, Sylvain Pion wrote:
>On Sun, Jun 28, 1998 at 06:51:00PM +0200, Andrea Arcangeli wrote: >> >I wondered whether there has been some thoughts about implementing an MMX >> >emulator in the kernel, something like the FPU emulator. It sounds like a >> >> Intel say that it' s impossible. From 24319201.pdf section 10.1: >> >> 10.1. EMULATION OF THE MMX INSTRUCTION SET >> >> The Intel Architecture does not support emulation of the MMX >> technology, as it does for floating-point instructions. The EM >> flag in control register CR0 (provided to invoke emulation of >> floating-point instructions) cannot be used for MMX instruction >> emulation. If an MMX instruction is executed when the EM flag is >> set, an invalid opcode (UD#) exception is generated. >> >> Andrea[s] Arcangeli > >Well, I already have a prototype (very very very alpha/dirty) that begins to >work. Cf http://www.inria.fr/prisme/personnel/pion/progs/linux if you're >interested. The emulation is actually done via the invalid opcode exception, >caught by the kernel, which in turn sends SIGILL to the process. What Intel >says is that they do not support hardware help for the emulation (and I don't >know what's the benefit of that anyway), but we don't need it.
Yes, I agree. Only sound me strange that Intel declare that is not possible. The phrase "The Intel Architecture does not support emulation of the MMX technology as it does..." sound me as -> "impossible at architecture level". Maybe it' s only yet another mistaken due my usual bad English ;-).
Andrea[s] Arcangeli
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