27 Jan
2014
27 Jan
'14
2:57 p.m.
The thread on using two RL02 drives with OS8 made me think about this, but I didn't
want to confuse that thread with my tangential topic.
Is there any difference in RL02 drives and/or disk packs for PDP-8 systems vs. PDP-11
systems (other than the obviously different controller cards for OMNIBUS/UNIBUS/etc.)? If
so, how do I evaluate and identify the specialized bits and pieces?
I ask this because I have a few RL02 drives waiting for my PDP-11/44 project, as well as a
pile of RL02 disk packs. If there are differences for PDP-8 vs. PDP-11 applications, i.e.
due to different word sizes, then I'll need to keep my eyes open for mismatched parts
in my pile. Conversely, if and when I get a PDP-8 system with an RL02 controller card,
I'll wonder whether I can use any of the pieces I already have.
I seem to recall reading in recent months about some DEC drive and/or disk pack that would
have different hard sector notches or some such thing for PDP-8 vs. PDP-11 applications,
but I don't recall which type of drive it was.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
27 Jan
27 Jan
7:14 p.m.
On 1/27/14 2:57 PM, "Mark J. Blair" <nf6x at nf6x.net> wrote:
The thread on using two RL02 drives with OS8 made me
think about this,
but I didn't want to confuse that thread with my tangential topic.
Is there any difference in RL02 drives and/or disk packs for PDP-8
systems vs. PDP-11 systems (other than the obviously different controller
cards for OMNIBUS/UNIBUS/etc.)? If so, how do I evaluate and identify the
specialized bits and pieces?
I ask this because I have a few RL02 drives waiting for my PDP-11/44
project, as well as a pile of RL02 disk packs. If there are differences
for PDP-8 vs. PDP-11 applications, i.e. due to different word sizes, then
I'll need to keep my eyes open for mismatched parts in my pile.
Conversely, if and when I get a PDP-8 system with an RL02 controller
card, I'll wonder whether I can use any of the pieces I already have.
I seem to recall reading in recent months about some DEC drive and/or
disk pack that would have different hard sector notches or some such
thing for PDP-8 vs. PDP-11 applications, but I don't recall which type of
drive it was.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
RK05 drives are hard-sectored, as you mention. RL02s are not, and the
same packs will work on either. The only hard constraint is RL01 vs. RL02
- you can't use an RL02 pack in an RL01 or vice versa. -- Ian K7PDP
10:45 p.m.
On Mon, Jan 27, 2014 at 5:57 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
Is there any difference in RL02 drives and/or disk
packs for PDP-8 systems vs. PDP-11 systems (other than the obviously different controller
cards for OMNIBUS/UNIBUS/etc.)?
None.
If so, how do I evaluate and identify the specialized
bits and pieces?
Dump the pack and look for interesting bit sequences. If you see an
RT-11 or ODS-1 filesystem, it's for a PDP-11 (or perhaps a VAX). If
you see an OS-8 filesystem, it's for PDP-8.
I ask this because I have a few RL02 drives waiting
for my PDP-11/44 project,
as well as a pile of RL02 disk packs. If there are differences for PDP-8 vs. PDP-11
applications, i.e. due to different word sizes, then I'll need to keep my eyes open
for mismatched parts in my pile.
Unlike older media, the RL01/RL02 packs have embedded servo data, so
you don't/can't do a low-level format in the field. As such, the
track/sector formatting is fixed, so each controller just fits in the
sector containers provided by the factory low-level format.
I seem to recall reading in recent months about some
DEC drive and/or disk
pack that would have different hard sector notches or some such thing for
PDP-8 vs. PDP-11 applications, but I don't recall which type of drive it was.
RK drives do that - the most likely model you are to run across is the RK05.
The drives are identical from box to box, but the packs have slits cut in the
hub that result in 12 sectors for 16-bit hosts or 16-sectors for
12-bit hosts but
the same number of bits per track.
For those, you _must_ have the right packs, and you did occasionally
low-level format them (they use a "grated scale" optical positioner and
are hard-sectors and do not have any track or sector positioning
information written on the pack.
In contrast, the RL01 and RL02 rely on factory formatting and _do_
rely on pre-formatted packs.
Bulk-erased RK05 packs are still useful (after re-formatting). Bulk-
erased RL01/RL02 packs are not.
I myself have 1 or 2 RL01 packs with OS/8 data (and stickers on
them to tell me what they are). Every other pack I have is legible
in either a 16-bit or 32-bit system. If I was ever worried about the
contents of a specific RL01 or RL02 pack, I would back it up
($ BACKUP/PHYS in VMS) then wipe it and reuse it in any system.
OTOH, I have exactly one 16-sector 12-bit RK05 pack. All the rest
of my RK05 packs are 12-sector for 16-bit machines.
-ethan
-ethan
28 Jan
28 Jan
7:44 a.m.
Very interesting. Thanks! My single RK05 pack has 12 sector notches. That is a relief...
If it had 16, then I would feel an even stronger need to procure a PDP-8 to go with it.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
Web page: http://www.nf6x.net/
8:33 a.m.
On Jan 28, 2014, at 1:45 AM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
...
RK drives do that - the most likely model you are to run across is the RK05.
The drives are identical from box to box, but the packs have slits cut in the
hub that result in 12 sectors for 16-bit hosts or 16-sectors for
12-bit hosts but
the same number of bits per track.
For those, you _must_ have the right packs, and you did occasionally
low-level format them (they use a "grated scale" optical positioner and
are hard-sectors and do not have any track or sector positioning
information written on the pack.
I assume diagnostics have a formatter in them somewhere. Failing that, the RSTS
initialization subsystem can format disks that support it, so a sufficiently old version
of RSTS that still has RK05 support can do this if you need it.
Incidentally, the 16 sector pack was also used in the IBM 360 model 44, which had an RK05
lookalike drive in the side of the main CPU/console cabinet.
paul
3763
days inactive
3764
days old
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