Due to my recent decision to heed The Call of The Valley, I need to move
my collection (about 6000 pounds of equipment) from Chicago to San Jose by
the end of next month.
I need to thin the herd some before the trip, so I will be posting a
message listing available equipment in the near future. Other than the
obvious suggestion of moving less gear, does anyone have advice for
undertaking such a move? We're thinking of using a professional mover or
a "you fill the container, we transport it" type of service if possible,
since driving 2200 miles (and over the continental divide) with a 10-month
old in a rented truck of questionable mechanical condition seems like a
bad idea.
The moving companies that I have contacted to obtain estimates have said
that the computer equipment is no problem - "just box it up". It sounds
easy enough, but I don't know what the reaction will be to 150-pound boxes
(or crates) that contain a single item. I'm planning to remove the front
panels from the lights-and-switches equipped minis for transport and may
remove boards and/or PSUs to lighten individual machines if necessary.
Does anyone have other suggestions for dealing with unwieldy items such as
rack-mountable equipment and workstation monitors in a long-distance move?
--
Scott Ware ware(a)xtal.pharm.nwu.edu
It would be well to remember that, back when hard-sectoring was common, it
was considered more efficient than soft-sectoring. Shugart 801 drives were
certainly available with hard-sector support as an option. Hard-sectoring
did cost more, hence died off quickly enough.
SInce this stuff is source code, if you have the ability to read it with one
or another ancient system, it might be well to look at the source files to
see what kind of FDC was supposed to be used.
Dick
-----Original Message-----
From: Don Maslin <donm(a)cts.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Thursday, July 29, 1999 9:44 PM
Subject: Re: 32 sector 8" floppies
<snip>
>>
>> Well... I suspect some of the early Tektronix development and perhaps
Unix
>> based systems, but the MITS Floppy Disk sub-system for the Altair
computers
>> used them.
>>
>> -jim
>
>And various versions of Wang equipment, IIRC.
> - don
>
>> ---
>> jimw(a)computergarage.org
>> The Computer Garage - http://www.computergarage.org
>> Computer Garage Fax - (503) 646-0174
>>
>>
>
>
<> work. The 5.25" floppy single density rate of 125kBITS/sec clearly would
<> fall below the spec. There are limits to the write pulse width as well
<
<You are still missing the point, totally...
<
<125kbps FM is _NOT_ 125kpulses/sec at the disk interface, as you seem to
<be implying.
I'm not missing anything. For FM that means the two frequencies are
125/250KHz. For MFM that is very not true. Different bandwidth, but still
not in the range of the accepted 250kbits/sec of the sony.
<Double Density, MFM, 250kbps.
<-----------------------------
<A bit cell is 4us long, so 250000 of them per second. There is a (data)
<pulse in the middle of a bit cell written as a '1', no (data) pulse in
<the middle of a '0'. There is a (clock) pulse written at the start of a
<bit cell if there is no (data) pulse in both this bit cell and the
<preceeding one.
Your missing bis/time vs frequency domains/bandwith.
<For MFM you need to be able to record/reproduce pulses with separations
<of 4us, 6us, 8us.
true and for the data I gave the 125kbits/sec rate is too low. As it's
minima was 250kbits/s is twice that! Part of the recording scheme is that
there are rules for continous strings of 1s and 0s, they arent permitted
to exist for clocking and bandwidth reasons.
<Oh, absolutely. But the FM at half the data rate meets that spec. It has
<to. I am not suggesting you could feed 300 baud data into a disk drive
<and expect it to work - it almost certainly won't.
FM at half the data rate is the 8" SD rate of 250kbits/sec... not 125k!
The 125kbits/sec is the 5.25" floppy single denity rate. The problem is
that the 2f domain is in the right range but the base rate is clearly not.
It's an off by 1/2 problem. The 3.5" drive was designed to reproduce
pulses that fall in the 250khz (minima) to 1.0mhz rate(maxima) so theres the
bell curve that your skirting using the 5.25" single density data rate.
The 8" rate 250kbits/S lands right in the range but rotation time being
different you need a different sectoring arrangement.
Allison
Well this week was not too bad just mostly books and parts. One the books I
got at the thrift was Digital Deli written in 1984 and full tips, insights
(for the time), and over 115 photos. It's a great read, another I got was a
little newer called Computers: Today and Tomorrow and came with a CD, the
disk is great. Got a complete set of manuals for the Rainbow 100. Some nice
commodore items also like modems and some devices I had never seem before.
Will get a list out later. John
There's probably an easier way to look at the issue of data rate versus
density on magnetic media. First of all, you must realize that every
head/media/rotation-rate combination has a maximal flux reversal density
with respect to time. Once you know that, you need merely understand how
many flux-reversals the heads must induce on the media in order to record
what will be recovered as a single bit.
When you look at the manuals which come with various drives and controllers,
etc, you get the whole shmear in timing diagrams. Unfortunately, these are
marginally misleading. The drive takes the data stream it receives, in most
cases, and divides it by two, using the complementary outputs of a flip-flop
to drive the circuitry which drives the read/write head. Each time it
toggles, it produces, effectively, a single flux reversal on the medium.
When the data is read back, it produces a waveform more closely resembling
what's in the "books" in that the flux change is "seen" as a pulse by the
read/write head. This feeds filters and timing circuits and conditioning
circuits which make it into precisely what's expected.
However, not all modulation schemes cause the same effect at the head. The
FM technique, with a clock always written "on schedule" (except for address
marks) and transitions written only for "ones" one can clearly see that FM
is an F/2F code, wherein modulation is at one of two rates, either the clock
rate, or twice that rate. MFM improves on that by encoding the clock into
its data by reversing the flux at more or less the same rate all the time,
except that it shifts phase, always positively, in order to avoid exceeding
the flux-reversal-density limitations of the head/media combination.
(That's the reason the first zero of each string of zeroes is omitted, and
that a zero between two ones is not written.)
For the reasons above it's not resonable to try to compare FM and MFM. The
data rate which has been used with 8" floppy drives has always been (AFAIK)
250 Kbps. The 125 Kbps rate was used with 5.25" floppies, but they came on
after the adoption of MFM as the "smart" modulation scheme, so they were
normally (except with RADIO SHACK computers) used with MFM. The way in
which this modulation technique was applied was not the smartest way in
which it could be done, but it did work well, fell well within the limits of
the the-available technology, and provided a substantial improvement over
what was previously done. The high cost of MFM hardware was what motivated
WOZ, at APPLE, to figure out a way to process the data himself into a scheme
which used both cheaper hardware and gave, effectively, density equivalent
to "double" density, thereby defeating the critics.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, July 30, 1999 4:42 PM
Subject: Re: Cromemco 4FDC, How do you format a disk?
>>
>> <
>> <But from my measurements, I think that it's very unlikely that a drive
>> <can tell FM from MFM. I will try it sometime to confirm this.
>>
>> True, but the timing is still important.
>>
>> The SPEC I have for a Sony MP-F17W-70D (11/1988) makes it pretty clear
>> that the acceptable rates are 250/500kBITS/Sec MFM with no discussion
>> of plain FM. So it's probable the 8" SD rate of 250kbits/sec would
>> work. The 5.25" floppy single density rate of 125kBITS/sec clearly would
>> fall below the spec. There are limits to the write pulse width as well
>
>You are still missing the point, totally...
>
>125kbps FM is _NOT_ 125kpulses/sec at the disk interface, as you seem to
>be implying.
>
>Let's consider what's actually written on the disk, using standard 5.25"
>data rates.
>
>Single Density, FM, 125 kbps.
>-----------------------------
>A 'bit cell' is 8us long, so 125000 of them per second. Each bit cell
>starts with a (clock) pulse. There will be a (data) pulse in the middle
>of the bit cell if the bit is a '1'.
>
>So, allowable pulse separation times are 4us (between the 2 pulses in the
>same bit cell, and between the data pulse in one bit cell and the clock
>pulse at the start of the next one) and 8us (between clock pulses if '0's
>are written to the disk).
>
>Double Density, MFM, 250kbps.
>-----------------------------
>A bit cell is 4us long, so 250000 of them per second. There is a (data)
>pulse in the middle of a bit cell written as a '1', no (data) pulse in
>the middle of a '0'. There is a (clock) pulse written at the start of a
>bit cell if there is no (data) pulse in both this bit cell and the
>preceeding one.
>
>OK, consider some data patterns. Here a ';' singals the start of a new
>bit cell, a ',' separates parts of the same bit cell :
>
>11 -> data pulse, 1/2 bit cell gap; 1/2 bit cell gap, data pulse. Space
> between pulses = 4us
>
>101 -> data pulse, 1/2 bit cell gap; 1 bit cell gap ; 1/2 bit cell gap,
>data pulse. Space between pulses = 8us
>
>1001 -> data pulse, 1/2 bit cell gap; 1 bit cell gap ; clock pulse, 1 bit
>cell gap; 1/2 bit cell gap, data pulse. Space between pulses = 6us
>
>So,
>
>For FM, you need to be able to record/reproduce pulses with separations
>of 4us and 8us.
>
>For MFM you need to be able to record/reproduce pulses with separations
>of 4us, 6us, 8us.
>
>Since the drive can't tell data pulses from clock pulses, there's no way
>it can distinguish continual '1's at FM from the same at MFM, or
>continual 0's at FM from 1010... at MFM. Therefore, if it can do MFM
>correctly, it can also do FM _at half the user data rate_.
>
>> Keep in mond most all of the floppies I know of do have a minimum due
>> to the read amps bandwidth (there is a banpass filter!) and the
>
>Oh, absolutely. But the FM at half the data rate meets that spec. It has
>to. I am not suggesting you could feed 300 baud data into a disk drive
>and expect it to work - it almost certainly won't.
>
>-tony
>
Hi All:
Does anyone have any information on the Tektronix 4041? I've got a
hankering to play with the IEEE-488 bus but can't see paying the
current prices that most people seem to want for a IEEE-488
controller for a P.C. I've acquired an Tek 4041 with 512-K and the
rom Basic development firmware and even the manuals. But I don't
have the (optional) keyboard OR the diagnostics tape. If I could
find this tape then I could simple use a RS-232 terminal for program
input. I've even got a nice HP 150 that could serve as a terminal,
but I need that tape!! Speaking of which, this thing uses a DC100
tape. Know where a soul can find any of these tapes for less that
$25.00 each?
I know that GP-IB controllers are considered kind of low life - but
for some reason I'm hooked on this one (could be the 68008?). Hell,
you know what? I'm afraid that old computers are going to be as
addicting as old analog synthesizers and Tektronix mainframe
o'scopes.
Thanks all.
Roger Goswick
ccfsm(a)ipa.net
Pete:
You want some advice, eh? Okay. These beasties support CGA
or EGA (you set this up from the setup screen-- No, I don't
remember the key sequence, maybe it was CTRL-ALT-ESC, I dunno),
and AFAIK, I'm pretty sure they support 1mb simms. (the later
models had VGA, and supported more memory).
It's a '286 CPU (in case you haven't looked), and while it can't
run '386 based stuff, worked fin for most MS-DOS appz.
How do you make it boot? Ha. You have to have either: 3Com
3+Start server software, or 3+Open Start (for OS/2 LanMan).
3+Start is a component of 3Com's 3+Share Network OS, and was
in direct compettiton with Novell Netware 1.x and 2.x.
MS-DOS based networking at it's best, yesindeedy. ;^)
Basically, you built a file that was just a bit image of
a standard DOS boot disk, with the necessary drivers therein.
The START service would then respond to the boot request from
the 3Station, effect a network connection, and proceed to
serve up the boot volume (volume name setttable via setup,
I'm pretty sure).
After booting, you would log on to the 3COm network. Pretty
slick for 1986, actually.
I think I still have all of this stuff somewhere, ifn you
want it. The only problem is, you'll need to dedicate a PeeCee
just to run the boot services (and whatever other network services
you want). An awful lot of work for just a '286, but still
fairly cool. You'll also have to dig up a pretty old ethernet
adaptor to put in the server.
Jeff
On Fri, 30 Jul 1999 16:59:52 +0100 "Peter Pachla"
<peter.pachla(a)vectrex.freeserve.co.uk> writes:
> Hi all, I've had these two "3Com 3Stations" (model 3C1100) lying
> around here
> for the past 5 years or so and I'd like to actually get them
> running.
>
> Does anyone have any technical details about them; in particular
> what sort of
> graphics adapter is built in (it looks like either CGA, EGA or
> MDA/Herc), what
> sizes of 30-pin SIMMs do they take (and how do you set the memory
> jumpers) and
> how the heck do you get them to boot via the network?
>
> Anyone able to offer ANY advice?
>
>
> TTFN - Pete.
>
> --
> Hardware & Software Engineer. Sound Engineer.
> Collector of Arcade Machines, Games Consoles & Obsolete Computers
> (esp DEC)
>
> peter.pachla(a)virgin.net |
> peter.pachla(a)vectrex.freeserve.co.uk |
> peter.pachla(a)wintermute.free-online.co.uk |
> www.wintermute.free-online.co.uk
> --
>
>
___________________________________________________________________
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<
<But from my measurements, I think that it's very unlikely that a drive
<can tell FM from MFM. I will try it sometime to confirm this.
True, but the timing is still important.
The SPEC I have for a Sony MP-F17W-70D (11/1988) makes it pretty clear
that the acceptable rates are 250/500kBITS/Sec MFM with no discussion
of plain FM. So it's probable the 8" SD rate of 250kbits/sec would
work. The 5.25" floppy single density rate of 125kBITS/sec clearly would
fall below the spec. There are limits to the write pulse width as well
but I'd bet the 1771 meets them as they are fairly narrow range for all
data rates and formats.
Keep in mond most all of the floppies I know of do have a minimum due
to the read amps bandwidth (there is a banpass filter!) and the
differentiators used to recover the read data. the head gap width also
sets the minimum data rate as well though to a lesser extent.
The easiest was to see this is record a track at different rates from
50khz through 1mhz and look at what comes out (or not).
Allison
Well... having sysgenned my 11/44 RSTS/E V9.7 system some time ago
to add RL02s (among other things), I have been unable to read/write
files to the RL02s, which otherwise appeared normal on the system.
(INITable, ERASEable, MOUNTable, etc.) Any and all file operations
aborted with a "?Device not available" message.
Using the recently acquired RSTS Orange Wall (from Bruce Lane), I
have discovered the answer to the problem: one must *create an
account* on the device after INITing, etc! [D'Oh!!] Once I did so,
the drive assumed it's rightful place in the System and seems to work
fine; I copied and erased and re-copied a diskfull of Stuff several
times.
>>WooHoo!!<<
NOW: at one time someone offered me a Bootrom for the RL02s so I
can boot the 11/44 from them instead of the (DB0:) Fuji SMD. I need
to go back into the mail archives and find that message again, but
in the meantime.. I am looking for a 23-751A9 ROM to fit in the
M7098 UBI. I will glady pay cloning/shipping/etc for it.
Until then I am going to try booting from the RL02 by toggling in
the loader code on the Console.
But not Tonite!
Cheers and thanks to all who offered help/advice!!
John
please see embedded remarks below.
Dick
-----Original Message-----
From: Marvin <marvin(a)rain.org>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, July 30, 1999 9:14 AM
Subject: Re: 32 sector 8" floppies
>
>Richard Erlacher wrote:
>>
>> It would be well to remember that, back when hard-sectoring was common,
it
>> was considered more efficient than soft-sectoring. Shugart 801 drives
were
>> certainly available with hard-sector support as an option.
Hard-sectoring
>> did cost more, hence died off quickly enough.
>
>Why was hard-sectoring considered more efficient? IIRC, the soft sectored
>disks had more capacity than a comparable hard-sectored disk.
The overhead for soft-sectoring reduced the number of sectors per track from
32 to 26. This meant that you had (32 * 128 . . . 5 bits + 7 bits . . . 12
bits . . . must be 4K) 4K bytes per track. Anyway, 32 has most often been
more than 26 in my book. In some cases not much more, but more, anyway.
Drives could be jumpered to increase the sector capacity by skipping sector
holes. I was looking at the circuitry just yesterday (in the course of
troubleshooting an 8-inch drive) and recall that they allowd for 8 and 16
sectors per track as well, simply by dividing the sector pulses down.
This was probably less efficient, due to the decisions made along the way,
though it didn't have to be that way. The additional capacity didn't have
to be simply doubled just because the number of sectors was halved. I
recall something about 8 sectors yielding a capacity of somewhat more than
4K bytes. This does add up, since there are 83,333 nominal bit times per
revolution, half of which were used for clock, of course, if FM was the
modulation scheme. Since MFM was lurking on the horizon, I guess the LSI
makers just decided to forget about hard sectoring. Nobody believed anyone
would ever want a floppy diskette format which yielded more than what MFM
would offer. It's just like nobody once believed that more than 64Kbytes of
memory were desirable in a home computer, right?
The difficulty arises from the general discontinuance of the manufacture of
the FDC's capable of dealing with hard sectored media. Both NEC and Intel
made a version which handled hard sectored media back in '76. It
disappeared from their repertoire by '78, though. NEC also made a digital
tape cassette controller which went the same way.
