asterisk users - Oct 2004 - Does use of riser cards in racks affects performance of PCI telephony cards ?

Hi,

I've read quite a lot about sensibility of Asterisk HW cards to interrupt
latency, ...

I don't know much about HW, but would like to know if I use riser card
(vertical adapter for 1-3 PCI cards that goes into one PCI slot) to put some
Asterisk HW cards on it in rack chassis - do I affect their performance in
regard of interrupt priority latency in comparison with normal placing of
each card in separate PCI slot?


Thanks in advace,

regards,

Robert.

On October 21, 2004 08:06 am, Robert Rozman wrote:
> I don't know much about HW, but would like to know if I use riser card
> (vertical adapter for 1-3 PCI cards that goes into one PCI slot) to put
> some Asterisk HW cards on it in rack chassis - do I affect their
> performance in regard of interrupt priority latency in comparison with
> normal placing of each card in separate PCI slot?
Each PCI slot has four interrupt pins.  Unless the riser card is shuffling 
these pins around like a normal PCI motherboard does, all the cards on the 
riser will share the same interrupt.

It's my understanding that part of the PCI spec is that any card should be 
able to use INTA-D as its primary interrupt source but I've never seen a
card
that actually lets you choose which interrupt line to use, in hardware or in 
the driver.  Pity, really.

-A.

On Thu, 2004-10-21 at 14:06 +0200, Robert Rozman wrote:
> Hi,
> 
> I've read quite a lot about sensibility of Asterisk HW cards to
interrupt
> latency, ...
> 
> I don't know much about HW, but would like to know if I use riser card
> (vertical adapter for 1-3 PCI cards that goes into one PCI slot) to put
some
> Asterisk HW cards on it in rack chassis - do I affect their performance in
> regard of interrupt priority latency in comparison with normal placing of
> each card in separate PCI slot?
If you are using server quality hardware, the riser will be more
advanced and will have a more complex slot than just a PCI slot. I can
tell you I have 2 server class machines running 4 port T1 cards on
risers in my colo rack.
-- 
Steven Critchfield <critch@basesys.com>