17 Dec
2025
17 Dec
'25
10:19 a.m.
On Wed, Dec 17, 2025 at 6:09 PM Paul Koning via cctalk
<cctalk(a)classiccmp.org> wrote:
The RK05F is very similar to a normal RK05. It has one platter,
actually in the plastic housing of a normal catridge, and no
user-removeable platter.
The front panel has no door, but has the normal switches and lights of an RK05.
There is no loading mechanism, or cartridge door opening thing.
Instead, the cartridge door is opened by hand when the drive is
assembled, and a plastic wedge fitted to keep it open. 2 tension
springs are fitted under 2 of the screws that hold the cartridge
together These are hooked onto the chassis to hold the pack down. The
hub is locked to the spindle with the normal magnetic ring.
There are electronic modifications to give twice as many cylinders and
allow the unit to appear to the controller as a pair of normal RK05s.
Needless to say when you switch from one 'drive' to the 'other'
(actually halves of the same platter) it has to do a seek.
I am told that if you remove the platter/cartridge from an RK05F and
put it back, it may not centre accurately enough to read the old data
reliably (this is why the removeable RK05s don't have 400-odd
cylinders). So you can field-repair them, replace heads, etc, but you
should do a backup first, then do a full format and restore the data
afterwards.
FWIW the HP7900 uses a similar pack (24 sector notches?) with a fixed
platter in the same unit.
On Dec 17, 2025, at 4:29 AM, Jim Davis via cctalk
<cctalk(a)classiccmp.org> wrote:
Yep, I had a few. The other platter sits under the cart, fixed, but using
the same spindle air handling and actuator. I don't remember if the RK05
had the extra fixed platter. I think not.
No. The only DEC drive that had removable plus fixed on the same spindle was the RC25.
I remember when RSTS added support for one of those to be your system disk. Having to
spin down the system disk in order to swap out the removable cartridge required some
interesting OS magic. (Basically, it had to freeze things while you did the drive spin
down/up sequence.) Supposedly we did that work because we had a big customer who wanted
to put one of those systems on each of their submarines. :-)
There was an RK05F, I think, but that was just an RK05 with the cartridge permanently
installed as far as I remember; not the schizoid drive like the RC25.
By the way, on the possibility of using those packs on other drives: RK05 has 12 sector
tracks, so 12 sector slots not counting the index slot. I thought I saw 12 but someone
said 8, if so those packs would be incompatible with the RK05.
Some vague memory says that the IBM 360/44 had a 16 sector pack, but I may be confused
with the RK08.
The RK05 used with the RK08 controller does indeed use 16 sector packs.
I've never seen an RK05F with anything other than 12 sectors though,.
-tony