Delay in copying Linuxbios to ram

Steve Gehlbach steve at
Thu Apr 24 15:19:01 CEST 2003

Deepak Kotian wrote:
> 3-4 seconds looks a long time, should uncompression of few 100 KBbytes
> take that long.
> Also, could someone please elaborate the signifigance of biosbase set with
> this reference.

biosbase defaults to 0xf0000 and I believe this region is automatically 
cached by linuxbios (maybe not?).  If biosbase is set to 0xffff0000, 
then in your config you need to set:

option XIP_ROM_SIZE= 0x01000000
option XIP_ROM_BASE= 0xff000000

This will cache the upper 16M of the 4G address space.  Basically, the 
chipsets generally map both to the same physical memory, the flash, ie, 
they aliasing 0xf0000 to 0xffff0000.  You can cover 0xf0000 with ram, by 
setting proper bits in the bridge, but not 0xffff0000.  But on startup 
by default most if not all chipsets alias the top 64k under 1M to the 
top 64k under 4G.  It all has to do with legacy, real-mode stuff. 
linuxbios is in 32-bit mode, though,  after a few initial instructions.


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