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Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)
keith wrote:
>> The 36-bit limit being reported as 40-bit is another one.
>
> It seems this is so stupid that Intel must not have been serious about
> AMD64 at all. Amazingly *stupid*.
I like to think of it as shade-tree engineering. Screw together some parts,
and fix the bugs as you use them. Worked for automotive hotrodders. 🙂
>> But as for the DMA MMU, I think that just an extension of Xeon's
>> 36-bit physical memory limitations problem.
>
> Wonderful, but my understanding that the I/O MMU was only 32b.
> Stupid! Come on Intel! This stuff is *simple*! One can speculate
> that they're trying to slow down AMD64 by *not* being fully
> compatable.
I don't know too much about this specific problem. I think it was sited as a
possible reason for why Intel's 64-bit performance was so abysmal compared
to AMD's. I don't think it's actually an errata in the Intel docs. It may be
simply speculation from some testers as the reason for Intel's slowness in
64-bit.
I can't even see a DMA issue being a problem with the CPU, I think it's got
more to do with the chipset. Afterall, DMA is used by peripherals, not
processors.
>> NX and size limit bug would probably mean that Microsoft won't even
>> bother to support 64-bit mode on those early CPUs, at least not
>> without a firmware upgrade.
>
> ...but will they (ever) support AMD64 on processors that work as
> expected?
You mean AMD64 processors in general or Intel's implementations of AMD64?
Yousuf Khan
keith wrote:
>> The 36-bit limit being reported as 40-bit is another one.
>
> It seems this is so stupid that Intel must not have been serious about
> AMD64 at all. Amazingly *stupid*.
I like to think of it as shade-tree engineering. Screw together some parts,
and fix the bugs as you use them. Worked for automotive hotrodders. 🙂
>> But as for the DMA MMU, I think that just an extension of Xeon's
>> 36-bit physical memory limitations problem.
>
> Wonderful, but my understanding that the I/O MMU was only 32b.
> Stupid! Come on Intel! This stuff is *simple*! One can speculate
> that they're trying to slow down AMD64 by *not* being fully
> compatable.
I don't know too much about this specific problem. I think it was sited as a
possible reason for why Intel's 64-bit performance was so abysmal compared
to AMD's. I don't think it's actually an errata in the Intel docs. It may be
simply speculation from some testers as the reason for Intel's slowness in
64-bit.
I can't even see a DMA issue being a problem with the CPU, I think it's got
more to do with the chipset. Afterall, DMA is used by peripherals, not
processors.
>> NX and size limit bug would probably mean that Microsoft won't even
>> bother to support 64-bit mode on those early CPUs, at least not
>> without a firmware upgrade.
>
> ...but will they (ever) support AMD64 on processors that work as
> expected?
You mean AMD64 processors in general or Intel's implementations of AMD64?
Yousuf Khan