This is a long story...

My new computer got some problems when I've attached 4 IDE drives. It run very slowly during BIOS initialization. Then, when Linux is loaded all goes well...

3/4 weeks ago, it couldn't read HDD (PC could only boot from Live CDs)... I've tried to partition some harddisk, but changes didn't took changes...
Once, Linux was started, giving me a lot of I/O errors (afetr init was launched)... misterious...

I've tried to setup BIOS, but the only chance I had was "Load Failsafe Defaults"... I've tried!!! It works now!!!

But I've noticed that hdparm could only select udma2, telling me that udma3/4/5 are not available...

5 minute ago I've select from BIOS "Load Optimized Defaults"... now works perfectly... selecting udma5 for all IDE drives (except DVD-RW, of course).

Somebody knows if this is a correct behavior, a BIOS bug, or my motherboard is broken in some part?

I hate to know there's something wrong in my hardware, even if it work correctly now!