[coreboot] [LinuxBIOS] [PATCH] v3: add a check for a termination member
tsylla at gmail.com
Sat Jan 12 18:51:21 CET 2008
Carl-Daniel Hailfinger wrote:
> Hopefully that's the worst case. Still horrible if we use 1 MByte ROMs -
> 5 seconds for reading the whole ROM is unacceptable.
Sort of tangential, but some asked for some measurements of speed of
reads on 5536. I did some tests reading 64KB sequentially from an
SST49LF002A on a 500MHz Geode LX platform. The numbers are all scaled up
to time to read 1MB:
905ms - normal config
897ms - with a 5536 PCI region config added for the ROM region
738ms - with the region config set to prefetchable also
This was just a rep movsd from the ROM to another memory location.
So that is about 1us/byte, getting better with better configuration.
Turning on a 5536 region config has the effect of making the reads get
decoded medium instead of subtractive on PCI. Prefetch will let the 5536
use its PCI buffers to prefetch data from the ROM, so it has a big
effect on sequential reads.
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