Maxim S. Shatskih wrote:
But the BIOS never sets the disks to native mode initially as far as
understand; the OS drivers will... (haven't seen anything in the
BIOS where I can select whether SATA works in compatibility mode or
not...)

This choice is made by BIOS setup. OS's drivers obey this choice.

Haven't found this (yet) in my A7V600's BIOS (VIA KT600 chipset)


Would the register mapping *change* once the OS drivers are
initialized?

No. This will require the driver restart, and, for a boot driver,
this is impossible.

- SATA disks 0 and 1 are accessed via the register task file used by
the disabled primary PATA channel, in compatibility mode (== perf
impact, cannot access both disks simultaneously)

Yes.

- the burner is accessed via the register task file used by the
non-disabled secondary PATA channel

Yes.

- SATA disk 0 is accessed in native mode via a specific register set
- SATA disk 1 is accessed in native mode via *another* specific
register set

Yes.

- the burner is accessed via the register task file used by the
non-disabled secondary PATA channel

Yes.

Does one *choose* among the two (BIOS setting)

For Intel 865PE chipset, this choice is in the BIOS setup only.

My A7V600 is VIA KT600-based...