Physical memory access with SystemV/AT

[Jeff Bowles]

In article <1019 at sdcc12.ucsd.EDU> mp1 at sdcc12.ucsd.EDU (Leroy Dorman) writes:
>In article <185 at focsys.UUCP>, larry at focsys.UUCP (Larry Williamson) writes:
>> I would like to do something like:
>> 	shmcreate 0x800000 800000 1048560
>> to create a 1Meg shared memory segment at the 8meg address location.
>
>Unless Microport put in a peek/poke-style function in to V/AT,
>(the Rel 1.0 from At&t didn't have one)
>there's no way to access physical memory from u-space...

If you mean dereference a pointer and you're changing a character on the
video screen, no, there's no portable way to do it. I am running Bell Tech
SVR3, and the only choice *I* have is to open "/dev/mem" and lseek(2) to
the location of the video buffer and write(2) out the places I want to change.

But it DOES work, folks, albeit slowly (1-2 milliseconds to update the screen
via one write(2) system call).

More info, send me mail. It's not that hard, but certainly clumsy.

	Jeff Bowles