jvb7u@astsun1.acc.virginia.edu (brinkmann jonathan v) (02/18/89)
In article <358@sky.COM> hamill@sky.UUCP (John Hamill) writes: > > Does anyone out there know how to play with memory beyond 64k >in a PDP-11 running RT-11SJ? I know there is a RT-11XM that can use the >extended memory, but I don't have a copy. I'm running PDP-11/23's on Q-bus >and need to address devices beyond the 16 bit boundary. The PDP-11/23 uses >18 bit addressing on the bus but can't be talked to as far as I can tell. >Specifically, I need to talk to 0x20000 (hex) using a Whitesmith C compiler. >Any suggestion would be appreciated to the maximum. Please reply through >E-mail. The easiest way to use the extra memory with RT-11SJ is to use the VM device driver to access it as RAM disk. Then you can use the standard file I/O routines. Otherwise, you have to manipulate the MMU registers yourself. I have done this in MACRO with partial success. I was able to access memory just fine, but had to disable all interrupts to do it so that the monitor wouldn't crash by having the I/O page mapped out when it needed it (thats where I put my 'window' into the extended memory. -------------------------------------------------------------------------------- Bradley's Bromide: If computers get too powerful, we can organize them into a committee -- that will do them in. ================================================================================ __ / / ) / / _ __ /--< __ o ____ /_ ______ __. ____ ____ (__/ (_)_/ <_ /___/ / (_<_/ / <_/\_/ / / <_(_/|_/ / <_/ / <_ ================================================================================ Dr. Jon Brinkmann Internet: jvb7u@Virginia.EDU Astronomy Department UUCP: ...!uunet!virginia!jvb7u University of Virginia SPAN/HEPnet: 6654::jvb7u P.O. Box 3818 Charlottesvile, VA 22903-0818 ================================================================================