RQDX3 on an 11/23?
Jerome H. Fine
jhfinexgs2 at compsys.to
Tue Mar 15 20:28:06 CST 2005
>Fred N. van Kempen wrote:
>>I have a PDP-11/23 and would like to add a hard disk. Would the RQDX3
>>be the way to go? What do I need besides the board itself and an MFM
>>drive? Obviously, I need some sort of cable to connect the two. Is
>>there anything else I need? Will RT-11 V5 support an MFM drive on an
>The RQDX3 is a great controller. Assuming you can get drives (not
>always easy!) you need the usual two cables, plus an RDRX distribution
>board, which splits out the signals. Many people just made a custom
>cable going from the RQDX3's 50-pin header to the drives, with some
>pullup R's added in.
Jerome Fine replies:
While I agree that the RQDX3 is a great controller, unless the
user has substantial hardware ability to connect a 50 pin cable
to the hard drive(s) with 34 pin and 20 pin edge connectors,
I suggest the use of a BA23 box which usually contains the
panel for the distribution of the RX50 dual floppy drive and
2 MFM hard drives - although the front panel normally has
buttons (READY / WRITE PROTECT) for just one hard
drive. The BA123 box usually comes with the distribution
board to handle the same RX50 floppy and 2 hard drives
or up to 4 hard drives with no RX50 floppy - although you
also require a SEPARATE assembly for the READY / WRITE
PROTECT buttons for EACH hard drive.
Being a person without hardware ability, I always choose
the BA23 or BA123.
>Failing that, I'd strongly suggest a SCSI controller if you can find
>(and afford) one, or, quite nice as well, an ESDI controller that
>does MSCP- it then basically presents the ESDI drive(s) as
>RAxx drives to the system.
These days, the hard drives might actually cost more than
the SCSI host adapter (controller). The "nice" part about
a SCSI host adapter is the capacity of the hard drives which
can be 4 GBytes for very low cost - a few dollars.
ESDI controllers are also now very inexpensive, but at least
ESDI hard drives are also very large (600 MBytes were standard),
but might also be hard to find.
>Personally, I use all of the above. ESDI is a very good middle
>way solution.. drives are available, cheap and fast.
I also use all of the above - when I use a real
PDP-11. 99% of the time, I now use an emulator
under Windows 98 SE since I require 132 character
text lines under KED on RT-11.
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