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Well, today marks the first of my blog entries on RSTS.org. Many of you know me from the #classiccmp channel, and in the past from the ClassicCmp list. The hardware I'm working with here is a real PDP-11, on which I'd like to have running as old a copy of RSTS as possible.

Here's the machine specs:
Serial No: AG43576
Model 11/34-DH (Originally...this just tells the original build spec)

11/34a (M8265/8266)
128KW memory (MS11-L)
Serial Line Unit (M7856)
SCSI controller (CMD CDU-720)...thanks Jason!
Ethernet controller (DELUA)

Media devices:
RX26 floppy drive
2GB Seagate SCSI hard drive

So recently I've been trying to get an OS on this thing. Good part: this controller will recognize just about anything that I can plug into it, and that includes using a SCSI-to-IDE adapter...yes, it really will use IDE devices without a problem, meaning I COULD, if I wanted to, use a CF card.

Well, the problem with RSTS releases is, that they didn't plan ahead for larger disk sizes, meaning I have to find a small medium to make it work. This used to not be a problem on the SCSIfied 11/23+ I had, because the UC07 can truncate and partition disks with no problem - no such luck on the CMD-720U.

What happens if you set up too large a disk, you ask?

"RSTS/E fatal initialization error."
by julian@twinax.org
Friday, August 21, 2009, 09:26 AM
3 comments 3 comments ( 28579 views )  |  
( 1.9 / 7 )

Tim Thompson

If your SCSI controller supports partitioning of a larger drive,
then, depending on the size of your drive, it may not be a problem.

If you're using a real SCSI disk device, it doesn't matter;
you can edit the MODE PAGE to downsize the drive.

I have a few IBM 2.1Gb drives that I did this to,
as well as some 18Gb Cheetahs. IIRC, I made the
max byte count 4194301 or there-abouts.

Monday, April 8, 2013, 03:36 AM

Julian Wolfe
v8.0. What "large disk mods" are you referring to? Are there patches available somewhere I'm not aware of?
Tuesday, September 15, 2009, 06:59 PM

Paul Koning
Which version? RSTS V9.5 adds support for drives up to 2 GB. It also attempts to handle oversized drives, but that isn't done quite right.

The issue is the file system: the earlier version tops out at 0.5 GB, while the "large disk support" mods allow it to go up to 2 GB. And since no one was building anything near that size in those days, there isn't any partitioning support.

Tuesday, August 25, 2009, 10:43 AM