Subject: Re: aperture driver (Re: XFree 4.0)
To: maximum entropy <email@example.com>
From: Oleg Polyanski <firstname.lastname@example.org>
Date: 03/14/2000 02:59:18
>>>>> "me" == maximum entropy writes:
>> By the way, does anyone know why aperture driver with P6 (and higher)
>> MTRR support is not in NetBSD-current/i386 branch? I almost wrote my own
>> MTRR support code before discovered an updated version of aperture LKM in
>> XFree86 4.0 source tree. It's not obvious place for searching updated
>> aperture driver.
me> The aperture driver you're looking for is in our -current xsrc tree.
me> I built it from there and it seems to work fine. But what exactly *is*
me> "MTRR support"? I'm not noticing any significant improvement in
me> performance or anything else, while running X with this driver.
Yep, it works fine but it's LKM and should recompiled almost any time
when after you synced with -current.
As for MTRR, below is the quote from Intel P2 manual:
The memory type range registers (MTRRs) provide a mechanism for associating
the memory types with physical-address ranges in system memory. For more
information, see Section 9.3., Methods of Caching Available. They allow the
processor to optimize operations for different types of memory such as RAM,
ROM, frame-buffer memory, and memory-mapped I/O devices. They also simplify
system hardware design by eliminating the memory control pins used for this
function on earlier Intel Architecture processors and the external logic
needed to drive them.
So, generally speaking, MTRRs help in precise L1 and L2 cache
tunning. People from XFree86 team claim it could boost performance
in 2..3 times. Did you notice already new GIMP speed? I did. Very
me> relevant dmesg output:
me> pci0 at mainbus0 bus 0: configuration mode 1 pci0: i/o space, memory
me> space enabled ppb0 at pci0 dev 1 function 0: VIA Technologies VT82C598
me> (Apollo MVP3) PCI-AGP (rev. 0x00) pci1 at ppb0 bus 1 pci1: i/o space,
me> memory space enabled vga0 at pci1 dev 0 function 0: 3Dfx Interactive
me> Voodoo3 (rev. 0x01) XFree86 aperture driver version 1.99b Pentium Pro
me> MTRR support enabled
me> -- entropy -- it's not just a good idea, it's the second law.