[OT] Memory Models and Multi/Virtual-Cores -- WAS: 4.0-> 4.1 update failing

[feizhou at graffiti.net (Feizhou)]

Bryan J. Smith wrote:
> On Wed, 2005-06-29 at 12:20 +0800, Feizhou wrote:
> 
>>I thought they have done away with the high memory bounce buffers?
> 
> 
> Correct.  On x86-64, they have.

Ok earlier you said:

"At more than 1GiB on Linux/x86, you must use a 4G+4G kernel
(this is the default) to see more than 960MiB.  This causes a
signficant (10%+) performance hit.  On more than 4GiB, it is
worsened as more extensive paging is used."

where does the performance hit for 4G/4G on Intel (whether ia32e or not) 
come from?