## MMPM/2 Device Driver Reference

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### Anomalies

The following anomalies currently exist in the use of the high-resolution timer:

Having multiple device driver's attached to the high-resolution timer has not been tested.

The high-resolution timer sets interrupts at 1 millisecond even if a slower rate would suffice. If one driver wants callbacks every 2 milliseconds and another wants them at 4 milliseconds, the driver could program IRQ 0 for 2-millisecond ticks, but it does not.

HRT_FREE_POINTER does not currently do anything.

While the high-resolution timer is taking interrupts, DOS sessions (VDMs) will not receive INT 8 or INT 1Ch calls. Only one device driver can receive interrupts on a given IRQ in OS/2; and VTIMER.SYS-the VDD that provides INT 8 and INT 1Ch services to VDMs-expects CLOCK0x.SYS to deliver IRQ 0 interrupts. Because the high-resolution timer gets IRQ 0 interrupts, CLOCK0x.SYS-and therefore VTIMER.SYS-cannot get them.