Interesting find

From: Jerome Fine <>
Date: Sat Jun 2 09:24:25 2001

>Chuck McManis wrote:

> In packing up my stuff to move it from the office building to a temporary
> holding facility in my garage, I discovered I had the other half of the MDB
> Unibus to QBus bus "interpreter" which the docs claim will allow me to
> either use Unibus peripherals on a Q-bus machine or vice versa. Way cool.
> This means I can set up my 11/34a to use the RQ11D talking to a ESDI drive
> in a BA23 box as its hard drive (plus an RL01) but this gives me much more
> capacity. I hope it works!

Jerome Fine replies:

Since even V5.03 of RT-11 allows for up to 8 * 32 MByte partitions for
the MSCP/DU(X).SYS device driver (the first version of RT-11 that did
provide for partitioned MSCP devices, you should really enjoy an ESDI
hard disk drive. If you do find a drive that is more than 256 MBytes or
eight partitions, you can still use the extra "devices" as data volumes
under V5.03, but just not at the same time since the limit in V5.03 is
eight drives at one time (DU0: => DU7:) out of the 256 possible partitions
on an 8 GByte hard drive (I guess that would be SCSI - not ESDI).

Of course, if you have V5.05 of RT-11 or later, that allows up to 64
partitions at one time after you do a SYSGEN. The PDP-11/83 that
I have available has 3 * 600 MByte ESDI hard drives. Eventually I
hope to add a 4th drive for scratch use - the RQD11-EC quad controller
allows only the first three drives to be WRITE PROTECTED with a
passive front panel - I use an alligator clip connected to the correct wire
on the 10-pin connector tied to ground at all times except when I decide
to write something to be saved on the hard drive - if you are using the
drive as the system device and you don't like the error messages about
the SWAP.SYS file, then "SET EXIT NOSWAP".

One minor problem is that until after V5.04G of RT-11, there was no
possibility of booting (even a software boot using DUP) since the boot
code had ONE missing instruction to set up the partition number. I have
fixed that in my version of DU(X).SYS for V5.04G and could easily
do so for V5.03 as well. In V5.06 of DU(X).SYS, the ONE instruction
has been added to the boot block code, but you can still boot only the
first eight devices via DUP (DU0: => DU7:) since there are only eight
entries in the boot block for the required map. I have also fixed that in
my version of DU(X).SYS for V5.06 of RT-11 and can now boot
D00: => D77: via DUP. The reason I found this aspect important is
that with the 3 * ESDI 600 MByte hard drives, is use:
D00: => D23: for the first 20 partitions on physical unit 0
D30: => D53: for the next 20 partitions on physical unit 1
D60: => D83: for the next 20 partitions on physical unit 2 with
ASSIGN D54: D80:
ASSIGN D55: D81:
ASSIGN D56: D82:
ASSIGN D57: D83:
and when I add a small ESDI scratch drive as unit 3 which can't
be WRITE PROTECTED, I will use:
D90: => D93: for the remaining 4 available partitions on unit 3 with
ASSIGN D24: D90:
ASSIGN D25: D91:
ASSIGN D26: D92:
ASSIGN D27: D93:
so that everything is easy to see and understand and all the drive
numbers have a bit of sense and order.

If you don't understand any portion of the above, ask some questions.
I hope the hardware works for you.

Sincerely yours,

Jerome Fine
Received on Sat Jun 02 2001 - 09:24:25 BST

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