DEC (Minc 11?) RX01 disks and PUTR

From: Don Maslin <donm_at_cts.com>
Date: Fri Apr 20 19:01:42 2001

On Sat, 21 Apr 2001, Tony Duell wrote:

________O/_______
        O\
> The RX02 'drive' is a lot more that what is normally meant by a disk
> drive. It's a rackmount chassis containing 2 floppy drive mechanisms
> (these are standard, 77 track units, but without the normal circuit
> boards on them), a power supply, and 2 DEC-designed PCBs. The lower PCB
> contains the electronics you'd normally expect to find on a floppy drive
> (stepper motor drivers, read amplifier, write driver, etc). The upper PCB
> is the disk controller -- it's an embedded computer using 2 2901 ALU
> chips, 3 2911 sequencers (or are they 2909s -- I don't have the prints to
> hand), 1K of control store ROM, RAM, TTL, and so on. This communicates
> with the interface card in the Qbus slot (or Unibus, or Omnibus, or..)
> via a special TTL level serial link.
>
> There is some buffer RAM on the controller board in the drive box. The
> interface can send commands to transfer the contents of the RAM to/from
> the host computer, or to read/write a given sector on the disk to/from
> the RAM. Reading a sector is thus a 2-stage operation. First you send the
> command to read the sector into the buffer RAM on the controller board.
> Then you send the command to transfer the RAM contents to the host.
> Writing is much the same in reverse.
>
> Point is, the RX02 data format is determined by the microcode on the
> controller board in the RX02 chassis itself. It can basically do 2
> formats -- the special RX02 one, and an RX01 one, which is compatible
> with other manufacturer's single-density disks (IBM 3740, etc). That's
> why an RX02 can read (and write) RX01 disks. The reverse is not true, and
> nor is it true that other machines that can read/write RX01s can read RX02s.
>
>
> > reasonable since the RX02s can reputedly read RX01 diskettes.
>
> It can. In much the same way that many double-density systems can read
> single-density disks.
 
Thanks Tony! I am a lot more knowledgeable now than when I started this
exercise. And thanks to all the others for their helpful input also.

                                                 - don
Received on Fri Apr 20 2001 - 19:01:42 BST