[coreboot] Need a bigger CBFS size. What's a save value?

David Griffith dave at 661.org
Tue May 24 09:44:10 CEST 2016

On Mon, 23 May 2016, David Griffith wrote:

> I'm experimenting with a Thinkpad T60p, specifically getting something 
> working that includes PXE and secondary payloads.  Apparently the default 
> CBFS size of 0x40000 is too small because the build process complains it 
> can't add ipxe.rom and guesses that there's no room.  Just now I tried 
> specifying a size of 0x200000, thinking that would work because I have a two 
> megabyte SPI flash chip.  I went through the procedures on 
> https://www.coreboot.org/Board:lenovo/t60 and 
> https://www.coreboot.org/Board:lenovo/x60/Installation which led to a T60p 
> that shows a black screen and is non-responsive.  So, I guess that was a 
> wrong value.
> So, what's a safe value for the CBFS size that will allow me to add PXE and 
> some other secondary payloads?

I think my problem wasn't really with the CBFS size, but some apparently 
incorrect advice I got from the IRC channel.  I was told that if I clip 
the SPI flash chip to a Beaglebone Black and flash that way then I don't 
need to do these commands prior to flashing (see 

dd if=coreboot.rom of=top64k.bin bs=1 skip=$[$(stat -c %s coreboot.rom) - 0x10000] count=64k
dd if=top64k.bin of=coreboot.rom bs=1 seek=$[$(stat -c %s coreboot.rom) - 0x20000] count=64k conv=notrunc

After trying various sizes of CBFS, pulling the nvram battery, and trying 
the dd switcheroo on a lark, I discovered that I /do/ need to do the 

I tried and failed to flash the SPI chip from the T60p itself, first 
setting BUCTS to 1.  After I pulled the nvram battery, BUCTS reported as 
being 0.

David Griffith
dave at 661.org

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