NEVILLE@UMASS-CS ("Neville D. Newman") (01/26/86)
> The uVAX-II has 8192 map regs to map the entire 4 meg (22 bit) QBUS > address space. Each map reg is a longword (32 bits) and has the generic What? If physical memory is limited to 4 meg, why is DEC selling 8 meg boards for these machines? -neville
info-vax@ucbvax.UUCP (01/28/86)
In article <8601271021.AA11074@ucbvax.berkeley.edu> you write: > >> The uVAX-II has 8192 map regs to map the entire 4 meg (22 bit) QBUS >> address space. Each map reg is a longword (32 bits) and has the generic > >What? If physical memory is limited to 4 meg, why is DEC selling >8 meg boards for these machines? > Physical memory is not attached to the QBUS. Peripherals are. So the 22-bit QBUS address space has to be mapped into the potentially larger memory space for the DMA data transfer. -- carl lowenstein marine physical lab u.c. san diego {ihnp4|decvax|akgua|dcdwest|ucbvax} !sdcsvax!mplvax!cdl