[asterisk-users] 8-span TE820 card and interrupts

Shaun Ruffell sruffell at digium.com
Wed Mar 21 10:18:44 CDT 2012

On Wed, Mar 21, 2012 at 12:45:37PM +0000, Tony Mountifield wrote:
> Over the years I have experienced a few interrupt issues when using some
> of the Digium E1/T1 cards with Zaptel drivers, and usually resolved them
> by disabling USB devices in the motherboard BIOS settings.
> Now more and more systems are coming without PS/2 connections, so USB is
> needed for the keyboard or KVM.
> I never knew whether these conflict issues were down to the design of the
> card, the motherboard, the Zaptel drivers or the kernel.

My personal experience is these issues were a result of the BIOS
using the system management interrupt to emulate a legacy keyboard.
I.e., so you could plug in a USB keyboard and boot DOS on the system
and have DOS think it was a PS/2 keyboard.

> I need soon to build an 8-span E1 system using the Digium TE820 PCIe card,
> and want to know whether I am likely to have to solve similar issues, or
> if they are now history with newer kernels and DAHDI instead of Zaptel.

The TE820, like the 5th generation dual/quad span digital cards,
have an ability to grow latency in the audio path to acommodate
systems that can't guarantee < 1ms interrupt service times. So I
would be surprised if you still have issues.

> I would be interested in any comments from anyone with experience in this
> area. Also, can anyone easily tell me in which version of DAHDI support
> for the TE820 was introduced? (If not, I'm happy to go and search SVN)

2.6.0 was the first release that supports the TE820. (or
2.6.1) will be tagged here very shortly.

> Finally, does anyone have a feel for how much CPU power would be required
> to run Meetme with DAHDI mixing if all 240 channels were active in various
> conferences? (Yes, I know about ConfBridge, but my application currently
> needs to use MeetMe).

240 channels in meetme comming from an 8-span digital card? I would
have to measure it...but my guess is a pretty beefy system. In this
configuration, more speed on less cores would serve you better than
more cores.


Shaun Ruffell
Digium, Inc. | Linux Kernel Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: www.digium.com & www.asterisk.org

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