[asterisk-users] [hylafax-users] asterisk, iaxmodem, hylafax quality problem

[Lee Howard]

Thomas Kenyon wrote:

>The weird thing is, looking at the motherboard manual for my test
>machine, The lower the Interrupt does not neccesarily mean the higher
>the priority. Eg. 8 to 15 have a higher priority than 3 to 7.
>  
>

Correct.  IRQ 2 bridges to IRQ 8.  Thus the priority order is:

0, 1, 2, 8, 9, 10, 11, 12, 13, 14, 15, 3, 4, 5, 6, 7

This is one reason why on modern Linux kernels where the ATA (IDE hard 
drive) driver is permitted to be very resource-greedy the serial ports 
on IRQs 3 and 4 can lose requisite attention for high-throughput serial 
devices (like Class 2.1 fax modems).  And just think of those poor, poor 
printers on the LPT port, IRQ 7...  The end-result is that the already 
slim pickings on IRQs gets reduced even further to a very narrow band 
for add-on PCI devices, usually just 9, 10, and 11 on many systems.  
This is one reason for APIC, although it's quite buggy in many kernels 
and motherboard BIOSes.

Lee.