On Mar 26, 16:16, Richard Erlacher wrote:
> I'm not sure I am the one who should wake up here. I would repeat "It
> doesn't matter whether the diskette is a 1.2 MB one or a 360K type" but
it
> does depend what sort of drive it is.
No, Fred is right. There are plenty of drives designed to use single
density or double density disks at 96 tpi, and disks cerified for such use,
and they work perfectly reliably for 80 tracks, SD or DD. Historically,
such drives predate 1.2M (HD) drives. Provided you use SD/DD media in a
drive using the correct write current, and providing there isn't any other
leftover rubbish for the wider heads in a 48 tpi drive, any reasonably
well-aligned 48 tpi will handle those disks just fine. However, no 48 tpi
drive I have ever heard of is designed to use HD 1.2M media, and if you try
it, it will give trouble sooner or later. All the evidence indicates that
the major factor is the magnetic coercivity of the media.
> [...] the fact that the heads designed for 48tpi will write a
> significantly wider swath on
> the diskette than the 96tpi drive can erase. Consequently, and I'll bet
> you've had this experience, you can format a bulk erased diskette to
48tpi
> with a 96 TPI drive and have it work for a while.
>
> The more the diskette is written, by the 48tpi drive, the harder it
becomes
> for the 96tpi drive to erase its writing,
Again, no. Providing you're only reading back the part overwritten by the
96 tpi drive, this is not true. It only matters if you both write with 48
tpi, overwrite with 96 tpi, and then try to read back with a 48 tpi drive
-- which is not what was being discussed. And it doesn't make any
difference whether the 48 tpi drive writes once or one thousand times, the
magnetic field strength is the same!
> and, of course, the 48TPI drive
> will have the most trouble because the signal not erased in the 96tpi
drive
> is perceived by the 48tpi drive as noise, while the signal written by the
> 96tpi is written at a lower level to begin with, since the drive relies
on
> the higher coercivity of the medium to generate a larger signal amplitude
if
> that factor is to come into play at all.
No, it doesn't rely on the higher coercivity, not when it's writing single
or double density. It only does that for High Density.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
At 20:39 12-03-2000 -0800, John Lawson dared me to...
> So... where's the detailed Swap Meet Report????
>
> We're waiting...
>PS: Post to The List if you dare... :)
Ok, I dare. ;-)
The Puyallup swap this year was quite crowded compared with last year. I
managed to sell a bunch of stuff that I didn't think I would, and some
stuff that I thought would sell (almost) didn't.
For the record, I sold all the Exabyte drives (the 8500's are holding here
for checks from the purchasers -- thanks, guys!) and the small UPS I had. I
don't think any of the buyers (with three exceptions) were classiccmp'ers,
but all business was appreciated.
There were equal amounts of joy and irritation with this year's event. On
the 'joy' side was, certainly, good sales. Add to that my finding of not
one, but TWO Amp 'Butterfly' tools (if you don't know what one is, you'll
have trouble appreciating it), plus some spare batteries for the pair of
radios I use for SwapComm and a nice mid-80's vintage Amprobe clamp-on AC
meter, and I think I did pretty well.
On the irritation side. One fellow showed up with a beautiful mil-spec HF
receiver. Those of you familiar with the radio side of things will likely
recognize the designation of R-2174(P)/URR, a.k.a. the Racal 6790. It was
in great shape, came with its manual and power cord, and had a sticker
price of $1,275.
Those of you who know this receiver will know immediately that this is a
bit exorbitant. In prime shape, they're worth about a grand, and that's
what I offered the fellow for it (knowing full well that I'd be going into
debt for six months to pay it off!).
He insisted on waiting until the end of the day. However, at day's end, I
came back to find him wrapping it up. Upon asking what was up, he told me
(rather brusquely) that someone had paid him $2,000 in CASH for it.
Initially, I was stunned. Not only was that over twice what the unit was
worth, but it astounded me that ANYone would be (a) walking around with two
grand in cash in their pocket, and (b) would use it to buy a mid-80's HF
receiver, however nice.
I walked away from that one fuming. In retrospect, and after talking to a
friend of mine, it is now my firm belief that the owner was lying through
his teeth in an effort to cover the fact that no one had been willing to
pay his outrageous sticker price. Here's why I think this.
1). He was wrapping the receiver up as if to ship it. If someone was crazy
enough to pay $2K for that unit, said buyer would have taken it with them
ON THE SPOT.
2). The seller's attitude throughout the day was loud, obnoxious, and
forceful on trying to sell things. Too forceful, in fact. He wouldn't
dicker beyond a certain point, and he seemed borderline arrogant in every
dealing he had with those around him. From what I could tell, he sold very
little that day.
3). His body language, as he was wrapping up the receiver, was most
definitely NOT that of someone who'd just closed a two-grand sale. It was
more along the lines of "I'm taking my ball and going HOME! To blazes with
this whole mess!!"
Anyway, that's about it. I deposited more back into the bank than I took
out to cover my purchases, so I think I did pretty well. Eric Smith came by
on Sunday to pick up the DSD-880's I had for him, plus some other goodies,
and it was he who bought my last Exabyte drive. Eric, if you're reading
this, thanks again and enjoy!
Guess I'll just have to do it again next year. Heck, I might rent a table
just to get in early. Let's hope that, if someone has a similar receiver
next year, they'll be more serious about selling it at a reasonable price.
Caveat (burp) Emperor!
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner and head honcho, Blue Feather Technologies
http://www.bluefeathertech.com // E-mail: kyrrin(a)bluefeathertech.com
Amateur Radio: WD6EOS since Dec. '77
"Our science can only describe an object, event, or living thing in our
own human terms. It cannot, in any way, define any of them..."
>> IIRC at least one of the RML winchester systems was a box about the size
>> of a 380Z with a PSU, ST506-interfaced drive and a SASI-ST506 interface
>> card. I assume the 380Z interface was a SASI host adapter or something.
that sounds like what I maybe have.... never seen a 380Z so I don't
know. I've got five or six 480Z machines though, three or four of them
with network interfaces, and then two big black metal cabinets - one
houses the hard drive, and from memory the other contains either
controller logic or floppy drives (these things have been sitting in
sotrage for the last 4 years, so it's been a while since I've seen
them!)
pretty nifty stuff though, I must dig them all out again some day...
(they were given to me along with my Diamond wordprocessor, which was
the main find, so I only ever powered up the 480's to check that they
could talk to the disk unit before they got stored...)
someday I will have the time and space to fire these things up again and
have a serious play around with them...
cheers
Jules
>
On Mar 28, 11:51, CLASSICCMP(a)trailing-edge.com wrote:
> On Mar 28, 20:15, Olminkhof wrote:
> >The cards are, from one end:
> >M7195
>
> 128 kbyte RAM
It's actually a MXV11-B Multifunction card, with 128KB RAM, and ...
> >M8067
>
> Another 128 kbyte RAM
Or maybe 256K
> 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.
... the MXV11-B has two SLUs, of the same type as a DLV11. It also has a
bootstrap (usually) which is vaguely similar to some of the 11/23+ ad early
11/73 bootstraps, and an LTC. And a million jumper posts. I have a
document listing their names/functions somewhere online, if you need it.
> There seem to be some (slight) behavioural differences depending on which
> serial port I plug the terminal into.
Well, the one on the left of the card, looking into it from the back, is
the console line, if that helps.
> 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.
Well, that should be running. As Tim noted, there isn't a disk controller
in your list, though. I'd expect an RQDX1 or maybe RQDX2 in that machine
-- more likely an RQDX1 if the drive is an RD50. If there isn't, it won't
do much. It might be worth trying to connect a terminal to the console SLU
and seein what happens when you start it. You can break into the bootstrap
routine using ctrl-C if necessary.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Picked up a next turbocolor station early this week and it powers up but is password protected, anyone know a quick way around this ? Thanks in advance John
On Mar 27, 18:44, Richard Erlacher wrote:
> ----- Original Message -----
> From: Pete Turnbull <pete(a)dunnington.u-net.com>
> > On Mar 27, 19:57, Tony Duell wrote:
> > > fact behaves like the second type above -- a 98tpi (80 cylinder)
drive
> Surely you mean 96 tpi . . . right?
I'm sure that was just a typo on Tony's part :-)
> I'm curious ... How do you "set" a
> 1.2MB drive to behave as a 720-K drive, i.e. use that type of medium? It
> seems to me that, at a minimum, the controller would have to be seriously
> involved as well.
Assuming the HD drive is correctly jumpered, you simply get the controller
to put a low signal on pin 2 (density) of the interface. On most drives,
that will also change the speed from 360 rpm to 300; on others, not.
> > 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.
> >
> The fact remains that there are diskettes specifically designated as
being
> 96TPI-certified, "QD" presumably for quad density, since you get twice as
> many tracks as with a double density diskette, which were, originally
sold
> at a higher price than the "360K"
Indeed, and I have lots like that, ie either "certified for 96 tpi" or in
a few cases, "QD". However, the differential is partly marketing, and
partly because manufacturers often tested 96 tpi disks more carefully for
microscopic blemishes -- a tiny defect might cause a disk to be rejected
for 96 tpi, but pass a test for 48 tpi. Many (most?) manufacturers used
exactly the same media/emulsion for both types -- I know for a fact that
Dysan and Verbatim did, although I also know that Dysan at one time made
disks that looked slightly different, and presumably those did use a
slighlty different coating.
> > > 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.
> >
> This would follow but for the technique used for writing radial alignment
> tracks.
I don't follow -- the instructions for my Shugart and Dysan alignment disks
clearly state that the disk is suitable for both 96 tpi and 48 tpi drives,
and lists the apropriate track numbers for the various tests, such as the
cats-eyes alignment test (and, yes, the track number for 96 tpi is simply
double the number for 48 tpi in each case).
> results I had and observed in others' lack of success certainly support
the
> belief that the media were not the same.
Perhaps you've been unlucky. I too have found some old 48 tpi media are
just not good enough, giving one or two errors, but most post 1980 are fine
-- and I suspect that's just the result of better quality control.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
>I have a copy of the Sharp PC 7000 boot disk if you would like a >disk
>image of it. Let me know and I can email a copy of it to you.
>
>Ernest
I already have a boot disk for this thing, but thanks anyhow.
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
On Mar 28, 1:26, Technoid(a)cheta.net wrote:
> In <38E04821.4B8943AE(a)mainecoon.com>, on 03/28/00
> at 01:26 AM, Chris Kennedy <chris(a)mainecoon.com> said:
> >Is this a Sun cdrom drive? Random SCSI cdrom drives are prone to not
> >working unless they have a sun-specific hack to make the ID string they
> >return something identifiable to the boot prom. Differing Suns have
> >differing ways of refering to CDROM drives, and some insist that the
> >CDROM drive show up as ID 6. Have you tried using the prom diagnostics
> >to probe the bus to see who is home?
>
> I figured the id6 thing out by inferring from other info I hit on the web
> which was pretty slim on specifics. The drive is 6 and is a Toshiba
> XM-3701b.
> Maybe I need a single-speed cdrom?
Some older Sun boot PROMs won't recogise a CDROM unless set for 512-byte
blocks. Although the 3601 and later Toshibas recognise the SCSI
mode-select command to switch from normal CDROM 2048-byte operation to
Sun/SGI 512-byte operation, older PROMs don't issue that command. I'm not
sure about a Sparcstation 330, but you may need a drive that can be
explicitly set (such as a Toshiba 3301 or 3401; some Sony and Hitachi
drives also have a switch or jumper.
You might also want to switch from the "old" boot mode (prompt ">") to the
"new" one (prompt "ok ") by typing "n". PROBE-SCSI, HELP, and most other
commands are only available from the "new" prompt.
> BTW there are issues with this machine
> I have not yet resolved such as a parity error on a simm and what I think
> might be a power problem.
I'd fix that first :-)
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
>> >M7195
>>
>> 128 kbyte RAM
>It's actually a MXV11-B Multifunction card, with 128KB RAM, and ...
>> 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.
>... the MXV11-B has two SLUs, of the same type as a DLV11.
Yeah, that makes more sense. I still don't know how his machine is
supposed to boot from disk without a disk controller, though!
--
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
