On Mon, Jan 12, 2004 at 09:03:06PM +0100, Camille Constans wrote:
On my IBM 80 Go, 7200 trs/mn
Before : IO_support = 0 (default 16-bit)
Timing buffered disk reads: 82 MB in 3.05 seconds = 26.89 MB/sec
After : IO_support = 1 (32-bit)
Timing buffered disk reads: 74 MB in 3.03 seconds = 24.42 MB/sec
No changes seen....
Yes, I/O mode is odd. Sometimes it makes a significant difference, other times not. I suspect the deal is that, at the hardware level, it shouldn't matter, since it is a 16 bit connection to the drive in either case. So the cases where it makes a difference are instances where the 16-bit mode of the controller is flawed, but the 32-bit mode isn't.
DMA and interrupt masking almost always have pretty big impacts, though.