Re: 2.1.111: IDE DMA disabled?

Gerard Roudier (
Thu, 30 Jul 1998 23:42:03 +0200 (MET DST)

On Thu, 30 Jul 1998, Doug Ledford wrote:

> Older Fireballs don't support tagged queueing. Newer Fireballs support it,
> but have fixed tagged queue depths (8 for the Stratus and 15 for the
> Tempest). However, the Tempest firmware will corrupt itself and become
> totally useless if you keep 15 commands open for the majority of the time on
> an extended basis. The drive will require a complete power cycle before it
> will come back to life.

Are these tagged queue depths so documentated by QUANTUM?

> The Atlas drives also have a fixed maximum queue
> depth of 32 commands, but will return QUEUE_FULL for conditions other than

Hmmm ...
I remember having read that the recommended queue depth for the Atlas II
on AIX is 38.
I did get a try with an Atlas II using 64 tags and I remember it was
capable to accept so many commands sometimes.
The Viking II is documented as accepting a fixed maximum of 64 commands.
Donnot know how it is supposed to behave in multi-initiator environment,
but my guess is that this is also the maximum for the total amount of
commands at any time and certainly not the maximum per initiator.

> QUEUE_FULL if it simply isn't capable of taking another command at the

A device can return QUEUE FULL status at any time when it receives a
tagged command. The initiator has no handle on the thing which is stated
to be full by the device. The SCSI specs are so about this status and are
not going to change AFAIK.


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