> Has anyone built a floppy drive from scratch? Without salvaging
> any mechanical parts or heads from an existing floppy? I'm
> assuming that electronic processing is not a problem (in
> principle) for either floppy disks or CDROMs/DVDROMs.
Yes, in the early days at of floppies, CDC reversed engineered by using
"brassboards" and hand made heads on a lead screw. Primitive but very
stable and we were able to read and write. Whole assembly weighed about
100 pounds so it wasn't anything you could sell. But it did the job.
And was pretty easy to build using off the shelf components.
Floppy media being contact recording saves most of the grief you get
when trying to recover hard drive data.
Tony Duell wrote:
Another possibiliy is to assume that some (non-working) drives are still
around, how hard would it be to get them working again.
For both the CD-ROM and the floppy, I think all parts other than the
head/laser pickup could be made in a good home workshop (Note, I am not
claiming _I_ could do it, at least not yet). Now the winding on a floppy
drive head could corrode and go open-circuit (this is a problem on some
types of recording head, I am told it was due to acid from the fingers of
the people who handled the wire when they were being wound). But I would
think the semiconductor laser and photodiodes in a CD pickup was much
more likely to fail with time.
GIven the head, I think the electronics would be doable. The floppy drive
would probably be easier, if only because all floppy heads used much the
same read chain, so if you could find data on any floppy drive you could
probably make something that would work. And if you get it wrong, you are
not likely to damage the head. Whereas the CD pickup is a more
complicated device to drive, if you get the laser current wrong it'll
either not work (current too low) or not work ever again (current too
high). And every manufacturer did his own thing, so you are not likely to
be able to find a published circuit that will work.
-tony
Another possibility to consider is that technology might offer new tools.
Some of the magnetic field imaging tools we use in the hard drive industry
could easily give a visual image of every bit on a floppy. (Those old bits
are so big that we could write several sectors into them now.) It would be
extremely tedious to go from an image to data, but it is possible. One of
the big problems would be understanding and translating all the different
formats. The early 8 inch single sided drives used a variety of recording
formats: FM, MFM, missing clock, etc.
On this new technology to recover old - has anyone on this list been
following the work being done on recovering sound from very old wax
recordings using a laser? I saw a fascinating description of it in one of
the IEEE pubs. They used the laser to track the path a needle would have to
travel. Then converted the laser position to an analog signal to audio.
Then a little DSP work to eliminate the clicks, hiss, etc. The original wax
recordings were too delicate or damaged to use conventional means. The
results were outstanding - one of the recordings was put up on the net for a
while.
I understand they are also using this laser technique to recover some of the
sound tracks on the early talkies. I've also read recently about recovering
very faded movie film by using short wave length laser scans, then digitise
the results, and restore the original grey scale by converting the relative
amplitudes. I haven't seen any of the results of this yet. Has anyone on
the list seen these restorations?
Billy
Any of the CDC machines that were multiples of 6 bits also used tapes like
this. The 8th bit was start of a file or page of memory. The 7th bit
indicated the start of the word - 12, 18, 24, 36 or 60 bits.
Billy
Our very own Chris Garcia has an interesting article on movie computers at:
http://efanzines.com/DrinkTank/DrinkTank29.pdf
For those who don't know what fanzines are, I will leave that up to Chris to
explain in some future issue.
Billy
>From: "Randy McLaughlin" <cctalk at randy482.com>
>
---snip---
>Intel changed the specifications of the 2708 a couple of times, later docs
>state it does not require programming from address 0.
>
>I have changed individual bits (only from a high to low, to go from low to
>high the entire chip must be erased).
>
>The later docs still state sequential writing but no longer require starting
>at 0 but I have written non sequentially and can swear by that. I wrote a
>program that verified before writing to speed up programming, this skipped
>many bytes and I used it to modify previously written EPROM's. The buffer
>in RAM was sequentially read but the writing was NOT sequential it would
>skip bytes when a write was not needed.
>
>Any byte can have high bits changed to low even if they were previously
>programmed.
>
Hi Randy
I recall the primary reason they wanted one to go through
the entire cycle was that it gave the particular spot
that was programmed a chance to cool down. I'm not sure if this
was actually a real problem or just a suspected problem.
I may have been an electrical issue with space charge as well.
Technically, you could skip locations that didn't need
programming but you should insert a delay equal to the
normal total time before programming the same location
again.
Anyway, that is what I remember.
Dwight
Dwight:
Actually what I'm going to do is build a few adapters for different
24-pin densities such as the 2716, 2732 and the 2532. I have a few tubes of
2532s so I'm going to try those by mounting a socket on a DIP header and
making the wiring changes between the two layers.
Rich
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Dwight K. Elvey
Sent: Monday, June 27, 2005 2:25 PM
To: cctalk at classiccmp.org
Subject: Re: Programming 2708's
Hi Richard
I have both a Byte Saver and a data I/O. If you'll send
me the EPROMs and the data, I can program them for you.
As was mentioned, It wouldn't take much to make an
adapter out of two machine pin sockets that could take
2716's to use in place of a 2708. Most of the pins are
the same. Just make sure to pull the pins that provide
the extra nasty voltages.
Dwight
>From: "Richard A. Cini" <rcini at optonline.net>
>
>All:
>
> OK, I'm ready to burn a modified copy of the Altair Turnkey Monitor
>into a 2708 to use in my 8800b as a test program. Lo and behold, my
>programmer won't do a 2708 -- it'll only go down to 2716. Naturally I don't
>have any 2716s around and the VG ROM board accepts only the 2704 or 2708
>(without modification).
>
> So I browsed around eBay and elsewhere to see if any other
>programmers support the 2708 and it seems that none do. They all start at
>the 2716.
>
> What programmer can I look for that has the ability to program a
>2708?
>
> Thanks.
>
>Rich
>
>Rich Cini
>Collector of classic computers
>Build Master for the Altair32 Emulation Project
>Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/
>/************************************************************/
>
>
>> What programmer can I look for that has the ability to program a
>> 2708?
I have a Softy 2 that can do it if you're really stuck.
> Not just that, the programming algorithm is different to most
> other EPROMs. IIRC you have to program all locations in sequence,
> giving each one a 1ms (IIRC) programming pulse, and repeat that
> 50 times.
Any bit in any byte can be individually programmed from 1 to 0.
There are no sequence requirements, the programming pulse is one
pulse of 50ms per location programmed.
> You can't program odd locations like you can in later EPROMs.
You can, it's EPROM microcontrollers like the 68705 that need to
be programmed in sequence.
Lee.
___________________________________________________________
How much free photo storage do you get? Store your holiday
snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com
I could still use a couple more NS MM5740AAE/N keyboard encoders. These
are in a 40-pin dip package. They can probably be found in old 1970s
keyboards.
I'd be interested in buying either just the chip or the whole keyboard if
you happen to find one surplus in your parts bin.
If you've got one, please contact me for sale/trade info.
Thanks!
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
'Computer Collector Newsletter' wrote:
> I wouldn't expect that New Yorker readers know what Fortran is.
> Surprised they didn't just make it Windows.
Well, clearly John Allain was reading the New Yorker -- after
all, he saw the cartoon. I'm also a reader.
I'm pretty sure both John and I know what Fortran is.
Any particular reason for your comment, or do you simply insult
large groups of people without thinking about it?
Glen
0/0
Hello,
I need a DSD interface card to fit the PDP-8. AFIK it should look like
this <http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5177260665>. I
have several other DSD cards including quad width and double width cards
for the PDP-11 and LSI-11 and I will swap any of them for the PDP-8 card
and I will toss in an original DSD 440 manual and DSD binder.
Joe
I've been promising it forever, and I've finally
posted the SVD source code up at www.theSVD.com.
If I'm not mistaken, you could now (theoretically)
create your own SVD from scratch based upon the
web site.
And for you SVD users out there that I missed with
my bulk e-mail, the latest version of the software
v2.2 is posted, too. BTW, contact me if you want
to get ahold of the latest firmware v2.3.
Regarding the source code, there are three different
pieces:
- GUI - the gui is programmed in TCL/TK so the
tcl source is up there. The SVD CP
distribution is actually a windows/linux
executable that is wrapped up with a
licensed distribution package, so that
isn't included. But the code should run
as is.
- Firmware - the v2.3 firmware is posted, and
includes a complete MicroChip PIC
implementation of the SVD. Let me know
if you have problems compiling. I'm the
only one who has compiled it to date.
The firmware implements the "virtual
drive" functionality including generating
the floppy data signals.
- PC Apps - the GUI makes use of 2 PC-based
applications to get the tough work done.
The source for these tools are posted too.
There are some neat things there, including
implementations of file systems for the
TRS-80, Heathkit, and Apple. Again, I'm
the only one who has compiled this code,
so let me know if you have problems.
DISCLAIMER - You use the software posted at www.theSVD.com
at your own risk. Do with it as you will. Change it.
Distribute it. Create derivative works of it. Make
money off of it (yeah right). Whatever. Please, however,
don't b*tch about bugs. By all means report them, though,
and I'll fix them. And PLEASE, don't b*tch about my
programming. I'm just happy/shocked that it all works.
Fortunately, I don't rely on my programming skills these
days. :-)
Eric
