[Asterisk-Users] Re: Generic X100P's

[Stephen R. Besch]

>>The facts about Zapata hardware is that there is no buffering. If you
>>miss an interupt, you miss data. Interupts are fired 1000 times a second
>>or as soon as 8 bits are collected on the 8000hz phone lines. 
> 
There must be at least a 1-byte buffer. There is no way you could ever 
get any reliability out of a card that only provided 125 us of latency 
overhead.

> That is pretty much what I said. The lack of buffering is a feature - 
> latency is the enemy in telecomunications. That is why I said 100-200us 
> should be acceptable. This should be redily aceivable, even with shared 
> interrupts.
> 
200us probably would be. And, you could probably get average interrupt 
latency that low. The problem is that in any real machine, even when 
operating in real time mode, maximum interrupt latency is much longer - 
sometimes in the ms range - and the standard deviation isn't that great 
either. If you don't believe it, hook a scope up to one of the active 
interrupt request lines on the bus. It's very revealing.

Stephen R. Besch