[Asterisk-Dev] Hardware details for the Digium TDM400P

[Steve Underwood]

For any PC made in the last few years, processing four lines of 
telephony on the host will barely load that host. Remember that if you 
buy a card like the Dialogic ones, you get very little processing power 
on the card. If can only do simple things like DTMF detection and 
elementary ADPCM compression/decompression. Any serious computing - 
like, say, a G,729 codec - still needs to be performed by the host.

When you look at larger scale work - T1/E1 scale and up - there are 
valid arguments for and against putting serious processing power on the 
card. For a four line card there has been no real technical argument in 
favour of on board processing for several years. There are some valid 
arguments related to product approvals in some countries, but those 
issues are also much less of a problem than they used to be.

Regards,
Steve


list at asd-group.com wrote:

>Thanks for the feedback - it sounds like the TDM400P is generally a well
>thought of card with a couple of minor problems (probably in the drivers)
>that aren't show stopping given the occasional power cycle.
>
>I think I'll use it, but I am a bit concerned about the level of PC
>horsepower needed.
>
>It has to go in a Via EPIA system with their C3 (Nehemiah core) processor at
>1.2ghz (with full speed FPU). That's supposed to be equivalent to a
>similarly clocked P3 or Celeron. 
>
>Will than be enough grunt for the TDM400P to power a SOHO system with one
>telco line and three internal extensions (ie one FXO and three FXS modules)?
>
>I wish that Digium would make just a one or two page "how it works" doc
>about the card and card-driver interaction. What registers does it have, and
>what do they do? When are interrupts generated, what for, and how frequently
>per call? Does it use DMA, and how? What does it do well? What does it do
>poorly? What could be improved on in the driver? How does the driver do
>things? You know, just basic stuff.
>
>It's not nice having to guess from driver code, which is hard to understand
>(esp the DSP code), possibly bug ridden (no offence) and not guaranteed to
>fully utilise the card's hardware facilities. A little bit of info would
>make understanding the lower levels of the software much easier.
>  
>