[Asterisk-Users] Multiple TDM400P's in a single machine

[Alexander Burke]

Hello, Marc!

At 06:24 PM 02/20/2006, you wrote:
>Can someone give me a definite answer as to wether or not you can 
>reliably run multiple TDM400P's in the same machine?
>I need 4 x FXO and 4 x FXS to connect to both the PSTN and existing 
>key system, but I have seen several threads suggesting that this is 
>not a supported configuration

According to "Asterisk: The Future Of Telephony":

IRQ latency
Interrupt request (IRQ) latency is basically the delay between the moment a
peripheral card (such as a telephone interface card) requests that the CPU stop
what it's doing and the moment when the CPU actually responds and is ready to
handle the task. Asterisk's peripherals (especially the Zaptel cards) 
are extremely
intolerant of IRQ latency.

Linux has historically had problems with its ability to service IRQs
quickly; this problem has caused enough trouble for audio developers
that several patches have been created to address this shortcoming. So
far, there has been some mild controversy over how to incorporate
these patches into the Linux kernel.

Because the Digium cards require so much, it is generally recommended that
only one Digium card be run in a system. If you require more 
connectivity than a
single card can provide, either replace your existing card with one 
of higher density,
or add another server to your environment.*

* Many people report that Sangoma cards are more robust when it comes 
to dealing with unpredictable motherboard
chipsets, and thus can handle sharing motherboard IRQ resources. 
Regardless, it is still worth considering
using multiple servers, as the redundancy that can be gained from 
this strategy can quickly offset the cost.

--
Alexander Burke, A+, CCNA
Kingston, Ontario, Canada