[coreboot] [Patch] SSE & SSE2

Joseph Smith joe at settoplinux.org
Wed Mar 17 00:34:05 CET 2010

On 03/16/2010 07:29 PM, Stefan Reinauer wrote:
> On 3/16/10 5:31 PM, Myles Watson wrote:
>> This patch selects SSE&  SSE2 in the socket if one exists (except for
>> AMD since there are many sockets for two models).
>> The reasoning is that sockets can support multiple models of CPUS for
>> intel, and SSE&  SSE2 settings need to be based on the least capable CPU.
>> It's all correct as far as Google tells me.
> Not as far as Wikipedia is concerned. I think we should be careful as
> this easily breaks the code in very nasty places (especially SSE chooses
> the registers for ROMCC, so this definitely breaks some boards)
> The settings have to be the most conservative, not the best possible.
> That means if there is a single CPU for a socket that does not have SSE,
> SSE has to be off for that socket. Choosing SSE to be on because there
> is a single CPU for that socket that has SSE will break other systems.
> http://de.wikipedia.org/wiki/Streaming_SIMD_Extensions
>> Slot 1 - SSE but not SSE2
> Slot 1 is used by Pentium II, but only Pentium III has SSE.
> Also, Celeron only has SSE starting from Coppermine. Covington and
> Mendocino don't have SSE.
>> Slot 2 - SSE but not SSE2
> I think this is also wrong. Slot2 was then Xeon slot, but it also
> started with Pentium II based CPUs, which do NOT have SSE.
>> Via C3 - SSE but not SSE2
> Only Nehemiah and newer have SSE. All Samuel, Samuel2, Ezra and Ezra-T
> CPUs don't.
> http://de.wikipedia.org/wiki/VIA_C3
> I stopped after checking three of the ones you changed, because all
> three are wrong.. I think the code should not be changed. It's likely
> that the whole table you were using to do the matching was not
> describing what we need but instead the "socket capabilities" (i.e. the
> biggest feature set usable with that socket)
Well then we are going to need a different solution......

Joseph Smith

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