Paolo Nenzi wrote:
> Hi all,
>
> I have read the thread on MTRR settings on Linux. While this subject is
> not specific to the BP6, I would like to ask for some clarifications on
> the subject. I have read the mtrr.txt file in the Linux Kernel Docs but
> understand very little.
>
> I have a TNT2 card with 32MB of memory. What are the best settings ?
>
> On the doc is written:
>
> BASE ADDRESS OF VRAM SIZE in HEX
> /\ /\
> || ||
> echo "base=0xf8000000 size=0x400000 type=write-combining"
>
> I should write: echo "base=0xe6000000 size="0x200000
> type=write-combining", where 0xe6000000 is the base address of
> prefetchable memory, as reported by cat /proc/pci:
>
> VGA compatible controller: NVidia Unknown device (rev 17).
> Vendor id=10de. Device id=28.
> Medium devsel. Fast back-to-back capable. IRQ 16. Master Capable.
> Latency=32. Min Gnt=5.Max Lat=1.
> Non-prefetchable 32 bit memory at 0xe4000000 [0xe4000000].
> Prefetchable 32 bit memory at 0xe6000000 [0xe6000008].
>
What does a cat /proc/mtrr say before you do this? I have NOT typed echo
"base=0xe6000000 size=0x400000 type=write-combining" > /proc/mtrr yet, but my
system reports the following:
$ cat /proc/pci
Bus 1, device 0, function 0:
VGA compatible controller: NVidia Unknown device (rev 17).
Vendor id=10de. Device id=29.
Medium devsel. Fast back-to-back capable. IRQ 4. Master Capable.
Latency=32. Min Gnt=5.Max Lat=1.
Non-prefetchable 32 bit memory at 0xe4000000 [0xe4000000].
Prefetchable 32 bit memory at 0xe6000000 [0xe6000008].
$ cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0xe6000000 (3680MB), size= 4MB: write-combining, count=1
Does this mean that I don't have to do anything--it's already done?
I asked about write-combining on the #linux IRC channel and some experienced
people have told me that I don't have to do anything. It is automatically
done if it can be by linux on boot. Is this true? If not, are the
performance increases noticable?
Christian
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