frobinso@cirm.northrop.com (Fletcher Robinson) (07/12/89)
Does anyone know if CPU main memory(RAM) in a 4D70GT is dual-ported ? i.e. is it accessible from the VMEBUS ?
jmb@patton.sgi.com (Jim Barton) (07/13/89)
In article <8907111747.aa25894@SMOKE.BRL.MIL>, frobinso@cirm.northrop.com (Fletcher Robinson) writes: > Does anyone know if CPU main memory(RAM) in a 4D70GT is dual-ported ? > i.e. is it accessible from the VMEBUS ? The answer is yes and no. Only the lower 8 megabytes of CPU memory are addressable from the VMEBus. For a description, see the 'system' file in /usr/sysgen. Better yet, buy a Power Series upgrade, and address everything in the world. -- Jim Barton Silicon Graphics Computer Systems "UNIX: Live Free Or Die!" jmb@sgi.sgi.com, sgi!jmb@decwrl.dec.com, ...{decwrl,sun}!sgi!jmb
ted@bangles.sgi.com (Ted Wilcox) (07/13/89)
In article <37817@sgi.SGI.COM>, jmb@patton.sgi.com (Jim Barton) writes: > > In article <8907111747.aa25894@SMOKE.BRL.MIL>, frobinso@cirm.northrop.com (Fletcher Robinson) writes: > > Does anyone know if CPU main memory(RAM) in a 4D70GT is dual-ported ? > > i.e. is it accessible from the VMEBUS ? > > The answer is yes and no. Only the lower 8 megabytes of CPU memory are > addressable from the VMEBus. For a description, see the 'system' file > in /usr/sysgen. Also, you need to note that the memory will answer ONLY to NON-PRIVILEGED data access requests (address modifiers 0x39 0x9). If you try to assert supervisory address modifiers, the memory will not answer. -- Ted. ted@sgi.com {sun|decwrl|pyramid|ucbvax}!sgi!ted