bqt at update.uu.se
Wed Jan 7 07:25:15 CST 2015
The standard RK8E do a select using just one pin, meaning you can have
at most 4 drives on the system.
The RK11 have a binary unit number encoding, meaning you can have 8 drives.
There was also a version of the RK8 controller which did a binary unit
selection. I don't remember the designation of that controller off my
head at the moment.
More fun is that the same pins were used for both binary and 1ofN
selection. I don't remember how on earth this was detected/handled by
the drives, as I don't remember anything beyond the unit setting rotary
switch on one of the boards of the RK05.
Ans in theory, you could have gone to 16 drives, since you had 4 pins.
But then again, I wonder if it wasn't some clever design using the 4th
pin as a way of indicating that the other 3 pins were a binary unit
number by making sure that you never had just one signal active...
On 2015-01-07 13:40, David Humphries wrote:
> Also the selection method is different between pdp8 and the 11, one used
> 1 of n and the other 3 binary digits, cant remember which is which but
> do remember I had a bit of a fiddle getting my ex 11 drive to correctly
> select on my 8.
> ----- Original Message ----- From: "Ian S. King" <isking at uw.edu>
> To: <marc.howard at ieee.org>; "General Discussion: On-Topic Posts"
> <cctech at classiccmp.org>
> Sent: Wednesday, January 07, 2015 12:58 AM
> Subject: Re: Resurrecting RK05
>> Keep in mind that the drive has an internal selector for drive number.
>> Something tells me that a competition between two drives would not be a
>> pretty thing.
>> On Tue, Jan 6, 2015 at 1:36 PM, Marc Howard <cramcram at gmail.com> wrote:
>>> I would definitely replace the foam around the squarish tube that
>>> air to the pack. That's the worst place for a foam particle to break
>>> On Tue, Jan 6, 2015 at 10:59 AM, tony duell <ard at p850ug1.demon.co.uk>
>>> > >
>>> > > I am also wondering, that since I have very few PDP8-sectored RK05
>>> > packs, and a ton of PDP-11 sectored
>>> > > packs, if , when I first power up the drive after it has been
>>> > up to the RK8E , I can put one of my PDP 11 > packs in there and
>>> spin > it
>>> > up, if the controller will be able to load the heads? I'd much >
>>> > sacrifice one of
>>> > > these packs if there are problems rather than risk one of my
>>> > PDP-8 sectored packs.
>>> > An RK05 will spin up and load the heads without a controller. It is a
>>> > good idea to have a terminator
>>> > fitted (otherwise noise on the interface lines can do interesting >
>>> > like cause write glitches, don't ask
>>> > how I found that out).
>>> > It does need a pack with the slotted hub so that the drive electronics
>>> > tell the drive is up to speed before
>>> > it tries to load the heads. But obviously a 12 sector (PDP11) pack
>>> > for that.
>>> > So yes, you can use a PDP11 type of pack to see if the heads will fly
>>> > though the drive is on an RK8/E
>>> > -tony
>> Ian S. King, MSIS, MSCS
>> Ph.D. Candidate
>> The Information School
>> University of Washington
>> An optimist sees a glass half full. A pessimist sees it half empty. An
>> engineer sees it twice as large as it needs to be.
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
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