Re: ADA, Windows NT and Real-Time (was GNAT R/T Annex and Win95)

[steved@pacifier.com@199.2.117.163 (Steve Doiel)]

In <317916B0.A5C@ccmail.orl.mmc.com>, "Brian K. Catlin" <tpcatlib@ccmail.orl.mmc.com> writes:
>processor clock rate !). NOTE: The granularity of the timer service on PC (Intel) 
>platforms is 10 milliseconds (ancient PC architecture standard).

Details, details but:  According to the OS/2 Control Programming Guide (regarding timers on
PC hardware) "On most hardware, clock ticks occur approximately 32 times a second, so each
tick interval lasts approximately 31.25 milliseconds."

The 10 msec number didn't sound right, since most of the real time OS's I've usd have had
a 10 msec timer.  But then again on the systems I've done they're mostly event driven
so the resolution of the system timer isn't that significant.

> To build a real-time system with a small latency window (less than 1 millisecond) 
>would require that you write your system as an NT device driver (you may also want 
>to get a programmable timer board for fine granularity timers).  But if your 
>latency window is larger, then writing it in user-mode is fine.
>
> -Brian
>-- 
>
>Brian Catlin, Sannas Consulting (310) 798-8930
>Contracting to Lockheed Martin Real-3D (407) 356-0637
>Windows NT Internals and Device Driver Consulting