Hi, the following patch has been committed to SYSLINUX to fix the C/H/S addressing problems in isohybrid MBR and isolinux.bin :
http://git.zytor.com/syslinux/syslinux.git/commit/?id=32c09027423f61c305e2423e52f5f69ecad8e2c0 diff --git a/mbr/isohdpfx.S b/mbr/isohdpfx.S index 17e1efe..f9e9691 100644 --- a/mbr/isohdpfx.S +++ b/mbr/isohdpfx.S @@ -175,12 +175,12 @@ next: /* Get (C)HS geometry */ movb $0x08, %ah int $0x13 - andw $0x3f, %cx /* Sector count */ popw %bx /* EBIOS flag */ - pushw %cx /* -16: Save sectors on the stack */ movzbw %dh, %ax /* dh = max head */ incw %ax /* From 0-based max to count */ - pushw %ax /* -18: Save heads on the stack */ + pushw %ax /* -16: Save heads on the stack */ + andw $0x3f, %cx /* Sector count */ + pushw %cx /* -18: Save sectors on the stack */ mulw %cx /* Heads*sectors -> sectors per cylinder */ pushw %bx /* -20: EBIOS flag */ The other part of the changeset proposed on 25 Mar 2017 is now committed as http://git.zytor.com/syslinux/syslinux.git/commit/?id=8739e2ff9ba3f92652c8df846924fd00e1ce2753 It fixes the problem that an early decision against LBA addressing after INT 13 AH 41 could push a non-zero CX value to the stack, which isolinux.bin would pop and interpret as instruction to use LBA addressing. (isolinux.bin is wrong here. It should only use LBA if bit 0 of the popped CX is set. But even that could be wrongly sent from MBR if not the "Clear EBIOS flag" fix is applied.) Have a nice day :) Thomas
