On Wed, Dec 17, 2025 at 6:09 PM Paul Koning via cctalk <[email protected]> wrote: > > > > > On Dec 17, 2025, at 4:29 AM, Jim Davis via cctalk <[email protected]> > > 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.
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. > > 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
