Jerome Fine <jhfinexgs2(a)compsys.to> wrote:
I agree there needs to be a SYSGEN to be able to use
all 3 * RL02 drives with the DL(X).SYS device drivers
and the hardware handles ONLY 18 bit addresses for
both the DYX.SYS and DLX.SYS device drivers.
BUT the RLV11 and the RXV12 from DEC also
managed to handle only 18-bit addresses. So the
DSD box was completely compatible with the stock
(distributed) V4.00 of RT-11.
However, V4.00 code in DY.MAC contained the
extra instructions to use a double-sided media which
would probably have been called an RX03. And
although those extra instructions had bugs (after all
they had never been tested) and were removed by
V5.00 of RT-11, I did fix the bugs and ran a DYX.SYS
device driver under V5.03 of RT-11 using the DSD
8" floppy as a double-sided drive. In addition,
I also added a bounce buffer in DYX.SYS so that
a user buffer above 256 KBytes could be used
with the 18-bit hardware addresses in the floppy.
Actually, for device I/O, it doesn't matter whether
one is using 16, 18, or 22 bit addressing. The PDP-11
I/O page is defined as from 28KW-32KW, which is entirely
within the range of 16bit addressing.
Dale Rogers
DEC/Compaq/HP