Re: Triton DMA
mlord (mlord@pobox.com)
Fri, 28 Nov 1997 18:25:44 -0500
Gerard Roudier wrote:
>
> On Thu, 27 Nov 1997, mlord wrote:
>
> > DMA transactions are *exactly* the same speed/timing as PIO transactions
> > (thanks to the same cycle time of 120ns, plus pipelining/prefetch in the
> > chipsets for the PIO transfers). Except for Ultra33 DMA, which *does*
> > include 32-bit CRC checking (far superior to parity).
>
> Could the Linux IDE guy explain to a Linux SCSI guy who does
> not want to die in ignorance, in which this 32-bit CRC is so
> superior to parity ? ;-)
A single parity bit will only detect odd numbers of bit errors
(1-bit errors, 3-bit errors, ...), not even numbers.
A 32-bit CRC will detect both even and odd numbers of bit errors.
-ml