Long delays for USB realbtx boot

Bruce M Simpson bms at incunabulum.net
Thu Sep 11 12:55:04 UTC 2008


I have hacked NanoBSD locally to deal with generation of images for 
booting off USB keys. I am using the RELENG_7 branch as real-mode BTX 
support is necessary to support USB boot.

During testing I noticed that whilst the images eventually boot, there 
is an extremely long delay before doing so, between when the BIOS reads 
the boot sector and when the BTX loader messages appear.

Test system           Time
Thinkpad T43          1m 40s
ASUS Vintage AH-1     1m  7s

Any ideas why this long delay is occuring?

I see this with MBR geometries prepared for both USB-HDD (255H/63S/xxC) 
and USB-ZIP (64H/32S/xxC) modes. I am not using the strict USB-ZIP mode 
where everything resides on the 4th slice (da0s4) at the moment, as it 
requires further NanoBSD patches.

I am not currently generating images sized to the entire USB key to save 
space and time, so the cylinder size is smaller than the physical media, 
this might also be a factor.

Thanks for any light you can shed on this.


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