[openbeos] Re: app_server: MMX/SSE help wanted

> On 2004-08-10 20:40:45 [+0200], Axel Dörfler wrote:
> 
> > What we could also do is to add another bitmap flag to force an 
> > ideal
> > alignment for the current CPU.
> 
> This would be perfect. 
> 
> One other thing: will the kernel have some kind of CPU feature 
> identification? A quick grep on the headers didn't turn up any 
> relevant hit 
> on MMX (only B_CPU_INTEL_PENTIUM_MMX*). A function returning the CPUs 
> features would be very useful, to write code like this:
> 
> uint32 cpuFlags = get_cpu_capabilities();
> if(cpuFlags & CPU_HAS_SSE) {
>  ...
> } else if(cpuFlags & CPU_HAS_MMX) {
>  ...
> } else { 
>  ...
> }
> 
> I already do it this way, using my own CPU ID routine; but this 
> should 
> really be a kernel function. Of course that routine should also 
> identify 
> all other relevant features, not only SIMD instruction sets. I can 
> write 
> that routine if you want, I imagine the kernel team has other things 
> to 
> do...
It's called CPUID, and even userland apps can use a syscall which 
returns the value of that opcode.
(note using the kernel's get_cpuid() instead of the opcode directly 
ensures it is run on the CPU you want, not any, even thougth SMP 
systems are supposed to have "ideally" equal CPUs.

François.

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