>From: "Philip Pemberton" <philpem at dsl.pipex.com>
---snip---
>>
>> o Reading disks
>
>Easy - start when you get an index pulse, then stop when you get another
>pulse. I'd be tempted to make the stop pulse lag a bit though, just to make
>sure there's enough overlap to be reasonably sure that you've got all of the
>data.
You need a little flexability here. I have a machine that
is hard sectored and used 8 holes per sector.
>
>> o Writing back a disk image
>
>See above.
It does need retiming and pre-comp added back in.
Still, just a software issue. I like the DSP because
it can actually analyze the particular media used
and generate a more exacting pre-comp than even
the best controller can. This would be great for
archiving since the recreated disk can be better
than the original.
---snip---
Go for it Phil!!!!!
Dwight
Hi, gang,
I've come across a DEC THZ02 external/stand-alone tape drive in a nice enclosure with what is labeled as a SCSI interface. It resembles DLT in terms of its cartridge style, but it doesn't look like any "normal" DLT drive I've come across before in that it has no manual density selection that I can find.
Details? Also, if anyone wants it (I certainly don't need it), I would be happy to send it along for the stunning total of $10 plus shipping.
Let me know... Thanks much.
-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"
>From: "9000 VAX" <vax9000 at gmail.com>
>
>On Mon, 14 Mar 2005 20:51:10 +0000, Jules Richardson
>>
>> What about cost? (irrespective of how the device physically connects to
>> the host machine)
>>
>> I forsee four goals to make it useful:
>>
>> o Cheap
>> o Simple to build by anyone with a few electronics skills.
>> o Open 'source' (all schematics etc. available)
>> o Easy / quick connectivity
>>
>> Catweasel seems to lose out on 1, 3, and 4 - and 2 isn't relevant in its
>> case. Can't comment on how nice its software API is as I haven't looked
>> at it yet, but doubtless a bunch of us on this list could come up with
>> something that'd cater for all tastes (plus the really low-level
>> software would all be open source anyway!)
>>
>> Personally I'm not a fan of a USB version though; I'd rather have
>> parallel as pretty much any machine has a parallel port - USB limits me
>> to newer PCs and Macs (plus software interfacing *might* be harder).
>>
>> Priorities seem to me to be (highest first):
>>
>> o Reading disks
>> o Writing back a disk image
>> o Decoding disk data on host machine
>> o Modifying disk data on host machine, re-encoding back to floppy
>>
>> Happily, that's probably order of complexity too, easiest first :) (I am
>> coming at this from a preservation point of view, rather than being able
>> to create disk images for use with emulators, say)
>
>Luckly I have experience with both ADSP2181 and a CPLD/FPGA. I built
>my own little board to read out the internal memory from an ADSP2181,
>designed signal generation board with ADSP2181, and wrote thousands of
>lines of ADSP2181 code. On the other hand, I built a QBUS MSCP SCSI
>with Xilinx CPLD and now working on an Altera CPLD.
>
>I didn't read much of floppy controller but in my preliminary opinion,
>CPLD/FPGA is a better fit. If you use a 2181 here, you utilize only
>the (synchronous) serial port which can be easily built with a CPLD. A
>CPLD on parallel port has another advantage, that you might be able to
>eliminate a microcontroller which I guess is needed for a USB
>sollution. I don't have knowledge of USB so please correct me if I am
>wrong.
>
>vax, 9000
>
Hi Vax
What you say is true. I would suspect that it would be
possible to do all of the work in a CPLD, even for the
USB chip that I saw. Still, the ADI device has enough horse
power to do a lot of data reduction. It also has the
possibility to handle the writing back to a disk,
including pre-comp. Again, all this has the possibility
to be done in the CPLD as well but I think that incremental
development in a software environment is easier than
>from a Verilog/VHDL level.
I expected to use the processors ability to analyze the
data to help to do data reduction from an over sampled input.
This could be done on a PC with just the raw data as you
state( again, even with the CPLD ). USB might not be fast
enough to handle the over sampled data. By local data
reduction, one can minimize the buffering requirements.
In order to make a open source that all can use, you'd
need to provide a compiler. ADI gives one an assembler
that can be use for free.
Still, if you went ahead and did this on your own, that
would be great! I'm not sure if I could find the time
to fiddle with it for at least a few months. All efforts
here will be greatly appreciated. Having the code in
Verilog/VHDL would also help to avoid obsolescent.
Chips like the ADI2181 only have a few years before being
obsoleted. Both should have the advantage that one can
add enhancements as other types of disk media are added.
Dwight
Can anybody give me any information about this drive ?
Would I for example be able to connect it to any more or less modern machine ?
Thanks!
Stefan Mansier.
On Mar 13 2005, 22:45, Randy McLaughlin wrote:
> From: "Pete Turnbull" <pete at dunnington.u-net.com>
> > Michael is correct, the exact function varies from drive to drive,
and
> > it always involves changing the write current. Some drives have
> > several jumpers to affect this.
> I have tried to research the issue further but can I find no
authoritative
> references to pin 2 being anything but an RPM select line.
> If anyone has an authoritative reference stating it was not used to
select
> rotational speed I will be happy to change my website stating that it
does
> have multiple uses.
[ ... ]
> Please note I am not looking for what people remember it does but
actual
> documents from a manufacturer. I tested it with a TEAC FD-55GFR and
sure
> enough it slowed the RPM when grounded.
Well, how about document 5fd0050a.pdf from TEAC's website, which is the
spec sheet for the FD-55GFR-XXXX range. Page 1 lists the
customer-selectable jumpers for -3xxx, -4xxx and -5xxx as including
"LG" and "I". Page 7 shows where all the jumpers are. Page 8 lists
the jumpers for -7xxx.
Page 13 states (the CAPITALS are in the original document)
---------------------------- begin ---------------------------------
LG strap: to select the logical meaning of the Hi/Normal DENSITY input
signal at interface line #2
LG Strap OFF ON
-------------- -------------- -------------
Density mode HIGH LOW HIGH LOW
I/F #2 signal HIGH LOW LOW HIGH
For an AT compatible system LG should be set to the off state.
I Strap:
Strap to select the rotational speed mode of the FDD for the Hi and Low
density modes.
---------------------------- end ---------------------------------
In other words, Pin 2 is the Density Select signal, and can be jumpered
to work so that 0V (signal active) sets HD and inactive sets low
density (SD/DD, or FM/MFM). Normally it's not fitted, so active (low)
sets low density and inactive (or open-circuit) sets high density -- as
you woould want for an IBM AT or similar.
The "I" jumper controls whether the Density Select signal *also*
controls the speed -- a *secondary* function of the Density Select. If
fitted, speed changes when density does; if not fitted, speed is fixed
at 360 RPM.
Pages 16-21 of the same PDF file on TEAC's website are a scanned copy
of TEAC's "FD-55-GRF-XXXX Instalation Guide" for use with IBM AT, which
clearly shows the factory settings of the jumpers, with neither "LG"
nor "I" fitted, so Pin 2 selects density as usual, and the signal on
pin 2 does not affect the speed, which is fixed at 360 rpm.
If you want more, I have data for Mitsubishi MF504C-310MP, on which
jumper SS sets single speed (360 rpm) without affecting density
selection, same for Mitsubishi M4854-35, Panasonic JU-475-2.AGG (jumper
AX makes density select on pin 2 be latched when drive is selected,
BX/CX/JX determine if speed is determined by density select or is
fixed, and 1M forces it to ignore the density select signal on pin 2),
and Fuji FDD5883AOK (Toshiba) which has a jumper from pin 2 to ground
labelled "DD" for double density and described as disabling HD (jumpers
DE/DX are described as to set the speed according to the density, or
fixed).
Think about this: All HD-capable 5.25" drives need a way to set the
density (by changing the write current) for either 300 oersted media or
600 oersted media. The drive has no way to tell on its own. Therefore
there must be some signal defined to do this. AT controllers can write
both densities at 360 rpm (they just use a 300kbps clock instead of a
250kbps clock), so they don't actually need to change the speed.
Therefore the signal previously unused (or, rarely, used in
non-standard vendor-dependant ways) on pin 2 is the density signal;
using it to reduce the speed is an optional extra.
Your FD55 happens to have a jumper fitted to make the speed change when
you change the density, that's all.
--
Pete Peter Turnbull
Network Manager
University of York
>it's a museum!!! Emulate hardware for display?
I agree, I?m running two 2883s on Access under simulation. I run a single
7900 on the TSB E version, and a single 2883 on the F version.
The largest real Access system I ever owned/ran had 1 7920 and 3 7900s. What
is that, about 47MB. So two 2883s at about 25 MB each would just over the
largest real system I ever ran.
If you want real drives, the most rugged of them was the 7900, IMHO. The
7920 was fine, but not as tough as the 7900. The 7905 was the one that
seemed to me to crash for no reason at all. I always held my breath when I
spun up one of those. It seemed as though every time I got one for my
inventory I would have one fail on a customer?s site. So I cursed that drive
so much that I would never even try to run one on my systems.
BTW
Jay, Al,
I have a set of 2100 Access micro-code. My brother has offered to take a
shot at making copies of the ROMs. He did it once before for me in the early
to mid 80s. Perhaps if he can make 2 copy sets, we could send one set to Al
to be read and archived, and when he?s done have him forward them to Jay to
test the copies in real hardware.
On Mar 11 2005, 12:44, Randy McLaughlin wrote:
> From: "Michael Sokolov" <msokolov at ivan.harhan.org>
> > Changing the RPM is an option on SOME drives, and for PeeCees to
work it
> > must be OFF. It is very useful for Classic Computers, though.
> >
> > The high density select signal (pin 2) may or may not switch RPM,
but it
> > always switches the write current.
> No, I have refered to the TEAC site and to WDC:
>
> WDC referes to pin 2 as speed select, their controller can be used
with
> either single speed or dual speed 1.2mb drives:
> http://www.wdc.com/en/library/legacy/controllerboards/1006mm1.pdf
Michael is correct, the exact function varies from drive to drive, and
it always involves changing the write current. Some drives have
several jumpers to affect this. I could show you several from my
collection like that. Some controllers work at two speeds, some at two
data rates. Some of the WD controllers can be configured either way.
--
Pete Peter Turnbull
Network Manager
University of York
On Mar 14 2005, 14:30, Randy McLaughlin wrote:
> 2.88 mb controllers use it one way, some 1.44mb drives use it
another, some
> 5.25" drives use it for one thing other another.
1.44MB drives, ie 3.5" drives, do not need to be told what density to
use; they use the media sense to detect that from the holes in the
diskette. Therefore if they use pin 2 at all, they usually use it to
signal to the controller whether the media loaded is HD or DD.
--
Pete Peter Turnbull
Network Manager
University of York
>From: "Pete Turnbull" <pete at dunnington.u-net.com>
---snip---
>
>Bad contacts in sockets, accumulation of dust and airborne detritus,
>and problems resoldering or modifying boards when they get older. It's
>the lighter silicones that cause the problems, though, and if you
>can find a modern grease that has a smaller spread of molecular
>weights, the problem will be greatly reduced. The difficulty is in
>getting rid of the silicones, as they don't wash off, and flow into
>holes especially when you heat them up.
Hi
Silicon grease has a negative coefficient over much of the
normal temperature range. I actually gets thicker with heat not
the other way around.
>
>I used to do a lot of commercial repairs, especially on 1980s micros,
>and I used to hate the ones where people had put gobs of heatsink
>compund on socketed chips. The compound contains lots of light
>silicones, which used to get into the sockets and cause bad
>connections, and then it was a pain to remove the socket and solder in
>a new one. Of course, the worst were the ones drenched in "contact
>cleaner" and WD40.
Don't confuse with heat sink compound. I actually put silicon grease
into sockets to improve contact. It is used by manufactures in many
places that require improved contact. Heat sink compound is nasty
stuff. It is not what I'm talking about. I have sockets that have
10-20 years of trouble free function with silicon grease in them.
From experiments that I did years ago when working for Intel,
silicon grease not only works well on sockets and edge connectors,
it help switches as well. Especially those that have particularly
high or low current. In the high current ones it helps to prevent
arcing. The improved contact reduces contact heating. In the low
current ones it reduces the need for contact scrubbing.
About the only bad thing I can think of is that one might
get it on the surface of a floppy disk. Any grease on the surface
usually makes writing the disk problematic.
I've never seen DC#4 cause a bad contact. I've seen many cases
where it has improved it enough that problems of contact over
heating are no longer an issue ( Molex connectors in pinball
machines ).
WD40 contains all kinds of junk. I've never had troubles soldering
when the joint had silicon grease ( DC#4 ) on it. In fact, most
cases, it almost works as well a flux by keeping the oxidation
down ( Also done while at Intel ). The only reason Intel didn't
use it after the experiments I did was because they feared that
pre-labled parts would get this on them and the lables would not
stay on ( a valid reason ).
Dwight
On Mon, 14 Mar 2005 der Mouse <mouse at Rodents.Montreal.QC.CA> wrote:
> >> A byte is the smallest INDIVIDUALLY addressable unit of data on a
> >> system.
>
> Well, it sounds reasonable, but probably isn't the most useful, as it
> would mean that, for example, the PDP-8 had 12-bit bytes.
>
> > The PDP-10 is an excellent example of when this isn't true.
> > The smallest addressable unit is a word, which is 36 bits.
> > A byte is, as noted, anything between 0 and 36 bits. Bytes are
> > stored in a word, as many as can be fitted. To access bytes on a
> > PDP-10, you have a byte pointer, which consist of a word address, and
> > a bit pointer, and byte size.
>
> That sounds a whole lot like a hardware-supported way of addressing an
> object of an arbitrary size in bits. And that would mean that bytes of
> any size *are* individually addressible.
>
> Or have I misunderstood?
Well, yes and no.
Please note that there are special instructions to deal with bytes in the
PDP-10. These instructions can deal with objects of arbitrary size (well,
0 to 36 bits anyway). However, most instructions do not deal with bytes,
and thus will not play with the bit field stuff, and only deal with a
simple plain address, which address a 36 bit word. Among these
instructions are such things as a normal MOVE instruction. So these byte
pointers are only handled by a few special instructions, that deal with
bytes. For all other purposes, the PDP-10 only deal with words, which
always are 36 bits.
Johnny
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
