Linus Torvalds wrote:
>
> Although it porbably does mean that the problem tends to be more in the 
> really bad mode0 case (600ns -> 150us/sector -> milliseconds for 
> multi-sector transfers).
..

Heh.. it's worse that that: even with commonplace mode4 (120ns) transfers,
each PCI bus transaction from start to finish often takes about 1us,
so for a 16-sector multi-sector read, that means 4ms+ with interrupts off.

> I forget what our multi-sector limit is, I think it tends to be 16. So 
> you'll never get _really_ long irq-off times, but "several ms" is still 
> pretty damn bad. 
..

It's a device limit, usually 8 or 16 sectors for nearly all drives now.

Cheers