HI,
I found one of these today. I also found the keyboard, external floppy
drive and monitor for. The "monitor" looks like it started life as a 8"
security monitor. But I have to say that this is the first monitor that
I've ever seen that was connected with a coaxial cable with N-connectors!
It looks like this computer was designed to control an audio visual system.
Can anyone tell me about the computer? I'm wondering if it's usefull for
a general purpose S-100 computer. All the cards in it including the back
plane are marked "AV". There are warranty stickers in it dated 1978 and it
has an 8080 CPU. Does anyone have docs and software for it?
Joe
A 1781? !!GAWD!! I've not seen even an oblique reference to that number
since back in the '70's. Wasn't that the one that died with MMFM? I don't
believe I ever saw one in the "flesh." Nevertheless, the difference between
it and any other member of the WD 8"-drive-capable controller line is
probably pretty minor.
Dick
-----Original Message-----
From: Dwight Elvey <elvey(a)hal.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Friday, February 04, 2000 3:09 PM
Subject: Re[2]: What's a WD2793A chip?
>"Richard Erlacher" <edick(a)idcomm.com> wrote:
>> That's correct, Eric, it's a direct replacement, functionally, for the
1793,
>> with an analog clock extraction circuit. It has the limitation that the
>> analog clock processing circuit requires a different lowpass filter for
8"
>> and 5-1/4" drives, and, IIRC for FM or MFM.
>
>Hi
> I have a iSBX card that I wrote a driver for that uses a
>2793. It is software compatable with the 1793. It does
>1.44M disk with the right clock. What I'd like to
>know is what are the software requirements for a 1781?
>Dwight
>
That's correct, Eric, it's a direct replacement, functionally, for the 1793,
with an analog clock extraction circuit. It has the limitation that the
analog clock processing circuit requires a different lowpass filter for 8"
and 5-1/4" drives, and, IIRC for FM or MFM.
The 9216 and 9229 are external clock recovery circuits tailored for the 179x
series, but can be replaced with a PAL. The 8-pin 9216 is pretty handy, but
doesn't handle the write-precompensation which the 20-pin (?) 9229 does.
Dick
-----Original Message-----
From: Eric Smith <eric(a)brouhaha.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Friday, February 04, 2000 1:46 PM
Subject: Re: What's a WD2793A chip?
>> In going through and sorting my piles of classic ICs, I ran across this
>> Western Digital WD2793A chip. What is it?
>
>It's a later replacement for the 1793 FDC. But not a drop-in replacement.
>It has an on-board analog data separator, while the 1793 required an
external
>data separator.
>
>Some of the other 179x replacements had better digital data separators.
>I've personally always had good luck using the 179x with external
>SMC 9216 or 9229 data separators, which are probably hard to get by now.
Hokay...
In my own opinion, most of the comments on the list about the reply-to
function preferred the "old" method. A fair number of the people who
preferred the "new" method have since publicly changed their mind. As a
result, the list now has the reply address set to the list which is how it
used to be before the move. I'd be happy to take any criticism for my
handling of the situation: send those emails to dev-null(a)tseinc.com
For the non-unix non-sendmail oriented on the list, that's a joke, don't
bother sending.
Now that the major issue appears to be resolved, I'm taking requests on any
other list behaviour that people don't like. I don't promise to implement
all of them, but I'll gladly take a look at it. Quite a few people sent
me... er.... "suggestions", but because of all the flurry of activity
related to the "reply-to" dilemma I didn't do a good job of tracking those
other requests. Here's what I can remember:
1) verify that digests are being built
2) check if the digests are sent automagically or does the list owner have
to "goose" them out
3) if they can be done automagically, get input from the digest users as to
how often they want them sent
4) Verify that digest people are on the digest list, not the non-digest list
5) See if users can be allowed to send to the list without getting daily
traffic
If you have anything to add to the above, please DO send in the request to
west(a)tseinc.com
Regards,
Jay West
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
> This is not really an OS issue. The PC disk controller can do MFM (and
> some versions can do FM) recording. In other words, if the 1581 uses MFM
> recording then most likely a PC controller can read its disks. If it uses
> GCR, then it can't _no matter what OS is in use_.
I meant that ISTR there is a utility that understands the 1581 filesystem
for Linux, as well as the hardware being able to read the raw format. Sorry
for the ambiguity.
-ethan
=====
Infinet has been sold. The domain is going away in February.
Please send all replies to
erd(a)iname.com
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--- Pete Turnbull <pete(a)dunnington.u-net.com> wrote:
> On Feb 4, 11:43, Ethan Dicks wrote:
>
> > The standard 5.25" drives _do_ use GCR for all native formats...
>
> I didn't know that. Did Commodore machines use a standard controller to
> write the MFM, or did they use the same techniques as for the GCR?
WD177x, AFAIK, in the 1570 (single-sided) and 1571 (double-sided) 5.25" disks
and the 1581 (3.5") drive.
> I know Amigas can read/write DOS disks, but they don't have any sort of
> standard controller.
Right. They can do MFM, GCR or whatever because the diskette interface
is distributed amongst several custom chips including a 4096-bit shift
register in the sound chip. The Amiga reads and writes an entire track
at once and parses it in memory. The MFM stuff is efficient because it
uses the masking logic of the graphic chip to convert MFM to binary and
back. With a simple adapter, you can attach Macintosh drives to the
Amiga and read/write _those_ as well (800K with a Mac drive, and 1.44Mb if
your Amiga has a C= half-speed floppy drive). There is a read-only demo
version of the Mac driver available, read-write is commercial software.
There's even a floppy-based network for the Amiga, but it's around $100
per node. I was just at the web page for it this week. RG-58 cable, bus
topology, and you can still have three floppy drives on the computer as well.
It's great for those bitty-boxes that have no slots.
-ethan
=====
Infinet has been sold. The domain is going away in February.
Please send all replies to
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If you love your old drives, you'll operate the stepper at it's optimum
rate, which should be essentially noise-free. If you can hear your drives,
you need to tweak the step rate, usually upward. One alternative is to ad a
mux or whatever to change the speed to the FDC when the step pulses are
being transmitted, as nothing else is happening then. Many drives need
rates somewhat faster than what the standard controller issues, hence, it's
a good idea to consider a fix, involving clock selection via the to match
the drive select.
In the case of the 1771 and 179x series it's possible to build a really neat
circuit I've seen but never tried to match, which uses the /TEST pin on the
FDC to cause the device to put out its pulses much faster, allowing them to
be accumulated externally in a counter, which, drives a DAC which drives a
VCO, which drives the counter as it downcounts the number of steps, thereby
slewing the head assembly. This could lead to an interesting but lengthy
discussion.
The point is that if you want your drives to suffer the least possible wear
>from off-rate stepping, you'll do SOMETHING to reduce vibration due to an
incorrect step rate. The vibration is on the same axis as the eventual
misalignment that will result.
None of this applies to the 1770/1772, which have reasonbly fast but not
fast enough step rates.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Friday, February 04, 2000 1:41 PM
Subject: WD1770 help needed
>> Hello all
>>
>> Sadly, the WD1770 fcd IC in my home-brew fd i/o board finally gave up the
>> ghost. Fourteen years of service is admirable -- when it finally
croaked, I
>> felt like weeping.
>>
>> Additionally, in violation of my policy of *always* keeping spares of
>> discontinued components which I use -- I have no spare.
>>
>> Does anyone know of a source for these? Or the 1772 (I believe Tony
Duell
>> once mentioned that the 1772 could replace the 1770 in most cases -- but
I
>> could be wrong).
>
>The 1772 appears to be identical to the 1770 apart from the step rates it
>uses. If your drives can take said higher rates, then the 1772 will work
>in your controller.
>
>The 1772 (although not the 1770) was, I believe, second-sourced by VLSI
>(the company that made most of the ARM chips), as it was used in Acorn
>Archimedes machines. The 1770 was used in later version of the BBC micro.
>
>The 1772 (I think) was used in Atari STs.
>
>I am not suggesting you raid a working example of any of these machines
>for the chip, but maybe somebody has a dead ST with a working 1772 or
>something.
>
>>
>> Also, I understand that the C64 floppy drives (1581?) used the 1770 but
I'm
>> not a commie and can't immediately verify this. Anyone out there with
junk
>> C64 drives who wants to liberate this IC -- to a good home??
>>
>
>The 1570 and 1571 (5.25" CBM drives that could read GDR and MFM disks)
>have a 1770 in them. Older CBM drives (1541, PET 5.25" drives) do not. I
>don't know about the 1581.
>
>Again, I'd not want to raid a working unit for the chip. But if you have
>a broken drive, it's a possible source.
>
>-tony
>
Thank you Jay and Derek... it's my opinion that the List is
better served by having the replies redirected back to itself.
Now, about that HTML filter...
Cheers
John
Hi,
I don't work for them or get any money for telling the list about it or
anything like that, but I found http://www.icmaster.com and it works most of
the time. It's best used to look up chips made by companies that are still
in business, though.
Will J
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