- IRQ sharing issues. Assign separate IRQs to each digium card.

- IDE drives have DMA mode set to on and that IDE drives are preferred
instead of SATA / SCSI, specifically because IDE drives can be set to
use UDMA2.

- IRQ misses are bad and should be minimised for the digium cards. This
can be checked using zttest application. Minimum acceptable value is
99.98%

- Avoid running X-windows on the box and disable frame-buffer by using
vga=normal on boot.

- If you still see irq misses, try using acpi=off and/or noapic

- Try disabling hyperthreading if it is enabled

See also

• Digium
• Asterisk Hardware
• Digium Analog Telephony Cards