Hardware:
-Gigabyte GA-6BXC rev 2.0 i440BX Mainboard (ATA33)
-Transcend 4GB IDE Disk on module (DOM) (ATA up to 133)

First I had the mainboard running the latest gigabyte BIOS and a 1GB DOM. The DOM was running on LBA mode IIRC, no problems. The normal BIOS is Award 4.51PG.

Then I wanted to upgrade to a 4GB size DOM. But the BIOS detected it wrong when in Auto, LBA or Large mode, as it identified it as just 1GB. So I set it to "Normal" mode and it ran fine with full capacity then. But it was not easy to get things set up, and some Disk managers and scanners give strange warnings. Scandisk for example: "last cluster inaccessible". Just a few warnings though, nothing noticeably slow or unreliable.

Now I flashed an unnofficial "Powerleap BIOS", which looks quite different as it is Award 6.00PG. It boots up much faster, no "plug and play BIOS extension" message. ACPI can now be disabled. Also it recognizes 4GB in LBA and Large mode. A keeper so far. But I still cannot use LBA or Large with the 4GB DOM because it will hang after the "Verifying DMI..." startup message. Only CHS mode will make things run.

Any Advise? Is Normal/CHS mode bad? How can one convert a disk between one format to another? without losing data?

Here is the Powerleap 6.00PG BIOS thanks to RG100: Link
There is also an unnofficial upgradeware tualatin BIOS, 4.51PG: Link

Edit: the 6.00PG BIOS has a downside... SoftFSB always fails when accessing the PLL-IC the first time after boot, only on the second try it works. And PC Player PCBench goes down from 23.3 to 22.3 FPS.