Can the person at Intel who wrote this SATA BIOS at least tell me what code 23 means? I guess it could be spinup/ready time but it is several seconds until the SATA BIOS posts so unlikely.
OK one more thing in common is all my O.S.'s are now installed on Hitachi drives (Deskstar 7k1000.C). I created a system image and restored it to a Samsung drive and the system booted under AHCI mode just fine. So more likely it is the drive make rather than the O.S. I have also heard of same issue with W.D drives. In all likelihood if I restore image to Hitachi it still won't boot but for completeness sake may try it soon....
And yet.....these are stock standard SATA II drives so what gives with the error 23. I have tried various drive settings with Hitachi HDD utility (power management, SATA interface etc, jumper on/off) to no avail. While at one level my problem has been solved, I would like to get to the bottom of this as quite a few people are having this problem who might not have the luxury of having another manufacturers drive.
Here is the solution to the problem for my Hitachi drive. (win 7 x64) (use at own risk)
1) take a system backup (including system image) of your boot O.S. with windows backup
2) create a system repair disk (DVD) with windows backup
3) delete the partitions on your boot drive (not sure if this is necessary)
4) boot to the repair dvd, follow instructions to restore latest system image
5) reboot, change BIOS settings to AHCI, reboot and all should be just fine.
For some reason the 1.20E AHCI BIOS just does not like to go past a disk that has a win 7 x64 IDE operating system on it, and restoring the image to the same drive seems to fix the problem.