----- Original Message ----- From: <[EMAIL PROTECTED]>
To: "Asterisk Users Mailing List - Non-Commercial Discussion" <asterisk-users@lists.digium.com>
Sent: Tuesday, April 12, 2005 2:20 PM
Subject: Re: [Asterisk-Users] DS3000P - 20 E1 capacity on single card
[EMAIL PROTECTED] wrote on 04/12/2005 10:51:49 AM:
Andrew Kohlsmith wrote:
> secondary card for DSP functions is very inefficient of the PCI bus. I'd be > curious to know if the Digium cards can even do PCI-PCI DMA.
The Digium TDM cards can DMA into any RAM accessible over the PCI bus, regardless of whether it is located on the motherboard or on a PCI card.
That's not the point. The point is that you have to transfer voice data twice: once from the DS3 card to the co-processor, and once from there to the eventual destination (probably system RAM). If the co-processor is integrated into the DS3 card that first transfer is handled and echo-cancelling is performed *before* the data hits the PCI bus.
In other words, a PCI-based co-processor would double the PCI bus bandwidth necessary. And with a latency-sensitive product like voice, bus contention is not something you want to add to! :)
Tim Massey
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