On Mar 27, 19:57, Tony Duell wrote:
> There is some wonderful confusion in this thread :-)....
Yes :-)
> The first is the standard density 48tpi drive. This is what PC owners
> would call a '360K drive'.
[...]
> The second is the standard density 96tpi drive.
[...]
> The third is the high density drive, known to PC users as the 1.2Mbyte
> drive.
[...]
> From this, it seems to me that a 1.2Mbyte drive will _not_ reliably
> read/write a 360K format on HD disks. It will use the wrong (too low)
> write current. HD disks should be used for 1.2Mbyte formats only.
>
> Of course when a 1.2Mbyte drive is set to use 'standard' disks, it in
> fact behaves like the second type above -- a 98tpi (80 cylinder) drive
> and not a 360K (40 cylinder) one.
Tony has put this very well. It's exactly what I was getting at.
Furthermore, the media used in 96 tpi standard density disks is, in my
experience, the same as that used in 48 tpi standard density disks. It
even says so in my CDC drive manuals. However, as we all (ought to) know,
the media for HD disks is very different.
> According to all the data I can find (which is not much), the centre
lines
> of the 48tpi tracks and the centre lines of alternate 96tpi tracks
> coincide. This means (amongst other things) that you can use the same
> alignment disk for both types of drive. It also means that a 96tpi drive
> can reliably read a disk formatted and written on a 48tpi drive (only).
> When the 96 tpi drive's head is on a suitable track it is reading along
> the middle of the track. It's going to read good data. That's why there's
> no problem reading disks that have been formatted/written in 360K drives
> using 1.2Mbyte drives.
>
> Now lets consider going the other way.
Tony and I are in very close agreement here as well. The only point I'd
add, is this:
Disks which have been written in 48 tpi drives, and not subsequently been
bulk erased, may be read in a 96 tpi drive; and if then overwritten by a 96
tpi drive, they will still be readable perfectly reliably by the 96 tpi
drive, but often not by the 48 tpi drive. Just as Tony (and others) have
said (and as I've been telling people for nearly 20 years). However, there
is a good reason that the process is sometimes observed to work to some
extent, and that has to do with the way the tracks are written/erased.
When the track is written, data is only written into the centre portion
(about 50% of the nominal track width). Either side of that, the erase
coils in the head write a narrow guard band, which occupies most of the
remaining track width. It may happen that the guard bands written by a 96
tpi drive are wide enough to erase a large proportion of the signal written
by a 48 tpi drive, and a 48 tpi drive might just manage to separate the new
signal from the relatively low level of the residual old signal.
I'm *not* advocating this as an excuse to write 40-track (or 35-track)
disks in an 80-track drive without prior bulk erasure. But it explains why
some people have found it works for them (even before manufacturers
streamlined the range of heads they made), though probably only with
limited permutations of drives, and limited (at best) reliability.
I'm well aware of the problems in switching between 48 tpi and 96 tpi. In
the early '80s, I made and sold a little addon for micros that might need
to read 40-track disks in 80-track drives. Because I was well aware of the
problem, I arranged it so that it could not only switch on double-step for
one drive, but could separately switch one of the drive selects between the
normal connector and an extra one. The device was normally used on BBC
Micros with twin 80-track floppies, and the extra connector was to connect
a third, genuine 48 tpi, drive.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
>The cards are, from one end:
>M8192
OK, this is the CPU, a KDJ11-A.
>M7195
128 kbyte RAM
>M8067
Another 128 kbyte RAM
>M8045
Depending on the letters that follow M8045, it's between 8 kbytes
and 64 kbytes of RAM. I'm guessing it's a fully populated 64 kbytes.
>M8059
Another 128 kbytes or 256 kbytes of RAM, depending on the letters that
follow the M8059.
>I've also found out that it ran Venix in it's first life. It was connected
>to a PDP8/A that I also have but can't do anything with because of it's
>state.
>I'm unclear about the switches and lights, but I have the run light on, the
>DC light on, the fixed disk write protect switch out and it's red light out,
>and the fixed disk ready switch out with it's green light on.
>There seem to be some (slight) behavioural differences depending on which
>serial port I plug the terminal into.
It's also particularly confusing, because you evidently have no serial
line cards nor disk controllers in the backplane. I have no idea
how you even got the ODT prompt out of the machine.
Look at the serial ports on the back of the machine, and the ribbon
cables coming from the inside of the cab kits. Which cards in the
backplane do these connect to?
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
On Tue, 28 Mar 2000 05:13:11 -0600 Gary Hildebrand <ghldbrd(a)ccp.com>
writes:
> yeah, I've seen stuff for the Amiga go for more than you could buy
> it new .
> . .
>
> Typical auction, or should we call it a feeding frenzy?
>
> Gary Hildebrand
> Amigaphile and purveyor of vacuum tube technology
Ain't that bizarre? Even more bizarre was when I picked up
an extremely scarce WD-1009 ESDI controller for < $10!
Contrary to popluar belief, there are bargains there. . .
________________________________________________________________
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The cards are, from one end:
M8192
M7195
M8067
M8045
M8059
There is an RX50 double floppy drive and an RD50 hard drive.
It's difficult to work out what these are cabled to as they all plug into an
interface behind the backplane.
I've also found out that it ran Venix in it's first life. It was connected
to a PDP8/A that I also have but can't do anything with because of it's
state.
I'm unclear about the switches and lights, but I have the run light on, the
DC light on, the fixed disk write protect switch out and it's red light out,
and the fixed disk ready switch out with it's green light on.
There seem to be some (slight) behavioural differences depending on which
serial port I plug the terminal into.
Hans
-----Original Message-----
From: CLASSICCMP(a)trailing-edge.com <CLASSICCMP(a)trailing-edge.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Tuesday, 28 March 2000 0:49
Subject: RE: PDP11/23 More dumb questions
>>Anyway, I start the VT220 before the PDP and it gives a message VT220
Ready.
>>I power up the PDP and basically get nothing at all. The only sequence
that
>>gets any response is hitting the halt button. The terminal then says:
>>165262
>>@
>>When I hit the Restart button after that nothing happens for about 2
>>minutes.
>>Then an "&" prompt appears.
>>Nothing I type in gets any response after that. Typing "help" gets no
>>response.
>
>The "165262 @" prompting is from ODT. ODT is a very simplistic monitor
>that lets you modify memory and registers and start or single-step
>through instructions in memory.
>
>165000 is a common (but not the most common) address to put a ROM'ed
>bootstrap at. I'm guessing that when you halted it it was either doing
>the self-test or waiting for an external device to come ready.
>
>The "&" prompt I'm not so sure about. It's possible that this is a prompt
>from the bootstrap monitor (some Emulex bootstraps will say that) or
>maybe it's from the OS/embedded application.
>
>>The machine is in a BA23 case and was a PDP11/23 I think, but has a
PDP11/73
>>CPU upgrade. There is a full height ST506 hard drive reputed to be 30Mb in
>>size, which spins and makes all the right noises.
>>Any suggestions?
>
>What would help the most of all is an inventory of cards in the backplane.
>If they're DEC cards they'll have a "Mxxxx" number on the handle. Third
>party cards you'll probably have to pull to identify. Also tell us
>the exact position of each card in the backplane, and what cards are cabled
>to what drives.
>
>I suspect from the less-than-perfectly-standard bootstrap address of
>165000 that you've got a third-party controller in there with on-board
>bootstrap, though of course there an infinite number of permutations that
>things could have been set up for!
>
>--
> Tim Shoppa Email: shoppa(a)trailing-edge.com
> Trailing Edge Technology WWW: http://www.trailing-edge.com/
> 7328 Bradley Blvd Voice: 301-767-5917
> Bethesda, MD, USA 20817 Fax: 301-767-5927
>
Howdy;
I've got an IRIS 3130 I recently rescued, along with a shocking pile of
tapes. Among these are what appears to be complete OS install tapes for
GL2-3.6 (SGI's UNIX didn't come to be called until the first 4D-series
machines were released) and 3.5r1.
For various reasons I am interested in performing a new system
installation. Booting from tape is (obviously) in order, and a tape
identifying itself as the "boot system" is present.
If I 'boot sq0' the QIC spins briefly and complains that it can't find the
default boot file. Supposedly there is a stand-alone utility called
'sifex' which can be booted from tape to initialize disks and the like,
but if that's on this tape it's not letting on. 'boot sq0:sifex' returns
with an error to the effect that 'sifex' can't be found on the tape.
I'm missing something but I don't know what. Am I trying to boot the wrong
tape, or is something else going on? I suppose it would be worth trying
to read a few of the QIC tapes while the system is up, but if someone
knows in the meanwhile what my problem is likely to be, it'd be helpful.
ok
r.
In a message dated 3/27/2000 12:35:30 PM Pacific Standard Time,
at258(a)osfn.org writes:
> I checked out our Altos, and the old one is a 580-10A, #43948. Apparently
> they made a lot of these little devils.
>
I believe the 580 is a Z-80 machine, not an intel 8080 processor. Another PN
used for the Z-80 is the MK3880P-xx where xx=speed & P=plastic case.
The '-10' indicates a 10 Meg HD. They could come with several different
brands of drives. CPM or MPM was usually the operating system. there is a
separate supervisor terminal port to administer the system. I think there
were three user ports and two serial ports, one for a modem and one for a
printer.
I had about 10 of these at one time. Sold the last during my warehouse sales.
I have had several up and running. They are easy. Plug a terminal into
console. Wyse 100 or 50 terminal emulation. usually 9600/8/N (Hmm I can't
remember the stop bits) Put a current limiter on the power line when you
power it up for the first time. Make sure it is warm (room temp) and not cold
>from storage.
Paxton
>Did you start with a bulk-erased (i.e. with a degausser) disk? And >is it a
>real 360K disk (and not a 1.2Mbyte one)?
>
>-tony
Yes, it was a real 360K disk, I just reformatted it in Windows (it will let
you choose between 1.2Mb or 360 formats).
____________________________________________________________
David Vohs, Digital Archaeologist & Computer Historian.
Computer Collection:
"Triumph": Commodore 64C, 1802, 1541, FSD-1, GeoRAM 512, Okimate 20.
"Leela": Macintosh 128 (Plus upgrade), Nova SCSI HDD, Imagewriter II.
"Delorean": TI-99/4A.
"Monolith": Apple Macintosh Portable.
"Spectrum": Tandy Color Computer 3.
"Boombox": Sharp PC-7000.
____________________________________________________________
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Get Your Private, Free Email at http://www.hotmail.com
I had a 2086 and THAT was a cool machine
(also a way to find an RD-54--because
it was the same drive!).
>
> I checked out our Altos, and the old one is a 580-10A,
> #43948. Apparently
> they made a lot of these little devils.
>
> M. K. Peirce
> Rhode Island Computer Museum, Inc.
> 215 Shady Lea Road,
> North Kingstown, RI 02852
>
> "Casta est qui nemo rogavit."
>
> - Ovid
>
<> So, would any of our UK members like a VAX 11/750? Possibly one tha
<>has a SCSI adapter?
<>
<
<I gather that these are quite big, how does it compare for size with my
<MicroVAX II with 5 RA81 drives (ie 2 19" rack units)?
the basic 750 box is a 40" (memory test) wide by 40" high rack. So it's
smaller than your dual rack microvax. It can be powered off 110V at
reasonable current so in the 230v world it's not a huge problem there.
<I would like to ask for it but if it is a roomful then SWMBO might throw
<me _and_ the VAX out of the house ;-)
Depends on the disks alongside.
Performance wise the 750 is still slower than MVII, though IO perfomance
can be much better due to unibus vs qbus. Though reasonable cooling and
basic maintenance they tend to run a long time with little effort.
Allison
>I have a complete doc set for the VAX GKS software (whatever
>the heck it is)
Graphics Kernel System, maybe? Sounds dimly familiar from the Core
graphics library for the Pro, unless I'm confusing it with something else.
John Wilson
D Bit
