[HECnet] Can we hook this up to a VAX or something?

[Johnny Billquist]

On 2011-08-23 20:50, G  ran   hling wrote:
On the original question...

Please see
http://en.wikipedia.org/wiki/Table_of_8-inch_floppy_formats

I'd say that this drive "can" be hooked to for example a VAX, even
though it would be more easy to use a PDP-11.

Well, the format of the media have little to do with if the device can be hooked up to a machine or not.
(And DARN! I realize I think of capacities in words, not bytes, which made a comment I made in a previous mail wrong. :-/ )

It would be equally easy to hook it to a VAX and a PDP-11, since they use the same bus, and the same peripherials. So, if you design a controller for a PDP-11, it will work on a VAX as well, assuming you have a VAX with the same bus as the PDP-11, that is. ;-)

When the interface gets ready and a driver software is written, this
would enable reading of IBM-diskettes with their data/code ;-)

Right.

I'd doubt that DEC-diskettes (RX01 or RX02) could be used, but that
might be me being just a little to negative...

You might be. The DEC RX01 format is just the plain IBM 3740 format. Single Side, Single Density. I have used plenty of IBM floppies in my RX01 drive...

The RX02 format, however, is DECs own, incompatible thing.

Also, the interface between the floppy and the controller is very different between the DEC drives and whatever IBM used.

One important question might be if this type of drive uses soft or hard
sectors. (Soft means one index hole per revolution, hard means one per
sector, ie often like 16/rev. IBM often used the latter in their
consoles for 370 etc.

The RX drives, as well as at least the IBM 3740 is soft sectored.

But I can't really remember if this is actually taken care of by the
drive or by the controller - I'd guess controller actually. That means
this drive might be successfully interfaced using for example an RXV21.

No. The DEC interface is totally different than any other contemporary stuff. It's a pure digital interface which is fairly advanced. The RX01 and RX02 drives have a microcontroller, which performs the requested actions for you, so the controller on the computer can be really simple. So for the RX drives, all interpretation of analog signals from the drives are handled in the drive, as is all low level format stuff and god knows what more...

One issue might be that DEC is stated to use 77 tracks, the IBM says
"usable tracks 74" - question is how many tracks the stepper motor
actually has accessible by other mechanics - possibly, this might be
more of a media concern.

Possibly. But I've used IBM media in the RX01 just fine. The RX01 manuals claims that the media in the RX01 is compatible with IBM 3740 Family of equipment.

Myself, If access to an 8" floppy for DEC-equipment is wanted, I'd go
for either true RX02 (though the drive is quite bulky), or a true 3:d
party driver, like BASF, possibly Fujitsu etc. Myself, I've got a couple
of double drives 8" 1/2-height (about 1 1/2") neatly packed side by side
in an 19" 1he unit that used to be connected to a micro-vax.

In my opinion, IBM hardware is often "odd", big blue was big enough not
to care for industrial standards, and is therefore at the best my second
choice...

:-)

	Johnny


Happy computing, anyway!
/G  ran

On 2011-08-23 19:08, Sampsa Laine wrote:
http://www.ebay.co.uk/itm/Vintage-IBM-6360-8-Disk-Drive-Displaywriter-/110732734202?pt=UK_VintageComputing_RL&hash=item19c82f6efa#ht_861wt_1145



-- 
Johnny Billquist                                   || "I'm on a bus
                                                                  ||   on a psychedelic trip
email: bqt at softjar.se                         ||   Reading murder books
pdp is alive!                                         ||   tryin' to stay hip" - B. Idol