nessus@athena.MIT.EDU (Douglas Alan) (11/16/88)
I know that it is possible to connect two VCB02's (GPX QDSS video
display controllers) to a VAXstation II, but I have never seen anyone
connect two VCB01's (normal QVSS video display controllers). Does
anyone know if this is possible, and if so, do you know how to
determine the CSR address of the 2nd VCB01?
|>oug /\lan
(or nessus@athena.mit.edu
nessus@mit-eddie.uucp)cdl@mplvax.nosc.MIL (Carl Lowenstein) (11/17/88)
In article <10461@eddie.MIT.EDU> nessus@athena.MIT.EDU (Doug Alan) writes: >I know that it is possible to connect two VCB02's (GPX QDSS video >display controllers) to a VAXstation II, but I have never seen anyone >connect two VCB01's (normal QVSS video display controllers). Does >anyone know if this is possible, and if so, do you know how to >determine the CSR address of the 2nd VCB01? VCB01's have two sets of addresses to worry about: the display memory and the control registers. The standard setup puts the 1/4 megabyte display memory starting at Q-bus address 017000000, which is the top of the 22-bit Q-bus space. This gets mapped to microVax address space starting at 0x3ffc0000. The (64-byte) register space is normally based at Q-bus I/O page address 017777200, which is mapped to microVax address space 0x20001e80. There are switches on the board which select different addresses. Address bits <21:18> of the display memory start can be changed, thus moving it about in 1/4 megabyte address steps. Address bits <12:06> of the control register base can be changed, in 64-byte steps. Caveat: "To take advantage of certain MicroVax architectural features when programming bit-map operations, the video memory always resides in the topmost 256 Kbytes of the I/O physical address space." Information from VAXstation II Technical Manual AZ-GLFB-MN (1985). -- carl lowenstein marine physical lab u.c. san diego {decvax|ucbvax} !ucsd!mplvax!cdl cdl@mplvax.ucsd.edu cdl@mplvax.nosc.mil