Re: About ioremap() and L2-Cache

Ingo Molnar (
Fri, 25 Jul 1997 11:56:41 +0200 (MET DST)

On Fri, 25 Jul 1997, Alan Cox wrote:

> > Asus' Award bios docs mention that enabling write-combining might crash
> > the 'puter... Is enabling write combining supported under Linux? ;)
> > (don't exactly want to set "dangerous" options in bios... 'due cmos
> > changes might be one-way only in some situations...)
> > [any other stuff I should know about ppro's under Linux?]
> Write combining is the sort of thing you want to enable from user space as it
> breaks a few video cards and works wonderously well on most. You can do this
> as root under iopl(3);

no i think you need real ring0 access, not iopl(3). But there is already
an apropriate patch for Linux at:

it's a kernel module to set MTRR's. Reports say it seriously boosts XFree
3.3 on PPro's.

-- mingo