Monday, 5 May 2014

There are still weird BIOSes about!

I had two issues reported this week concerning booting .imgPTN images from E2B USB drives. Both issues show that even in the last few years, we still have BIOSes which have non-standard boot behaviour!

1. Intel Desktop Mainboard DP67BG

Art found that .imgPTN FAT32 image would not boot on this one mainboard but would boot OK on all other systems he had. It turned out that the partition geometry had to be set to 255 tracks per cylinder and 63 sectors per head instead of 128x63. I have now (v0.027) changed the default in MakePartImage to use 255x63.

2. Lenovo Thinkpad Edge E525 laptop

Alexandre found that on this laptop, it would not even try to boot from a .imgPTN FAT32 image but would boot OK from the same image via UEFI and boot to the E2B partition OK. It turned out that the .imgPTN FAT32 partition needed to be flagged as 'Active' (bootable) otherwise the BIOS would not try to boot from the USB drive in MBR\CSM mode! This was easily done by renaming all his .imgPTN files to .imgPTNA and now they all boot fine.

I am reluctant to always set the partition as Active as it may prevent some UEFI systems from booting (they may not like an 'Active' FAT32 partition and may only boot from it in EUFI mode).

The UEFI specification clearly states that the Boot Flag field '...shall not be used by UEFI firmware'. This does not appear to be the case for the Lenovo UEFI firmware!

If you see any similar behaviour, please let me know.