[coreboot] Timings v2

Marc Jones marcj303 at gmail.com
Mon Apr 20 18:17:43 CEST 2009

On Sun, Apr 19, 2009 at 8:38 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> I did some local optimizations and have some more info.
> I disabled keyboard init in coreboot-v2 - saves 400ms.
> I disabled ATA reset in SeaBIOS on first boot.
> I exit out of a CBFS search in SeaBIOS if the file signature is zero
> (CBFS is zero padding instead of ff padding).

You could also only read it once and save the devid and address of
ROMs if there are any.

> This brings the boot time on reset to 1.7 seconds (reset press to grub
> launch - doesn't include 2.5 seconds at boot menu).  Boot from powerup
> takes a bit longer - 8.9s (7 seconds is for drive spinup).
> Another optimization I could make would be to reduce the 90ms it takes
> to copy the vga rom from flash.  Using 4 byte reads instead of 1 byte
> reads will likely help.  However, enabling an mtrr for the flash would
> likely lead to the best results.

We have been discussing this in another thread. The 4byte read will
make the most improvement and the cache only helps a lot if the ROM is
compressed. You are still bound by the width and speed of the ROM
access. LPC/FWH is typically setup to be very slow.



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