Datanumerics DL8A is here! Have a peek _at_ ...

From: Joe <rigdonj_at_intellistar.net>
Date: Fri Mar 6 22:12:48 1998

At 12:11 AM 3/7/98 +0000, you wrote:
>> Trouble is, he's in Australia not in the US. The ROMs are going to have
>> to be shipped unless someone in Au has a 1702 reader.
>
>I supose the solution is for him to build a 1702 reader (which is a lot
>simpler than the programmer!) and to read the EPROMs himself. The problem
>is that the 1702 uses at least one strange voltage (a -9V supply, I
>think), and if you make a mistake when building the reader you could ruin
>the very chips that you're trying to save.
>
>The ultimate solution would be for somebody to program a 'spare' 1702
>with a known byte sequence, and use that to test the homebrew reader. A
>lot of work, though.
>
>I am still a bit worried about sending irreplaceable chips by mail. I've
>had a number of old computer bits sent to me, and AFAIK there have been
>no problems - in fact the Customs haven't even opened the packages. But
>murphy's law states that the package that contains those EPROMs will be
>the one that's suspected of being a bomb and blown up, or the one that's
>X-rayed with a sufficient dose to damage the chips, or the one that's
>lost, or whatever.
>
>
>>
>>
>> >You probably don't need to make a copy _now_. Just make sure the EPROM
>> >images are backed up onto something permanent (paper tape ? :-)). Then
>> >somebody can burn you a copy in the future if you need one.
>>
>> He had ALSO better back it up to something newer than a paper tape, paper
>> tape readers are getting hard to find. In fact, since 1702s and
>
>I thought most members of this list had a pair of optical paper tape readers
>fixed in their faces :-)

  Yes, but my optical readers never were that good to begin with and they
certainly haven't improved with age :-( And the memory that it's connected
to acts like a buffer, FIFO, if you know what I mean.

>
>Seriously, good paper tape reading machines are going to last almost for
>ever - there's not a lot to go wrong with them. And I'm quite sure
>there'll be _somebody_ with one in the future.

   Perhaps in a museum.

>
>I didn't mean that paper tape should be the only backup - keep a copy on
>disk, on CD, on DAT tape, on whatever. Hopefully it will remain useable.
>Use it as an image to disassemble, and to make replacement EPROMs. But
>having a copy on a known-almost-permantent storage medium can also be useful
>
>> programmers for them are getting rare, I think someone should engineer a
>> 1702 replacement out of modern ICs that can be programmed on a modern
>> equipement. Then match the storage media to that equipment. Given the
>
>It's called a larger EPROM with the higher address lines tied to ground :-)

   Except that -9 V is still sitting there.
>
>2764's are so cheap now that it's worth using one as a 256 byte (or 1K,
>or whatever) EPROM and wasting most of the chip.

   That's what I mean, just a piggy back board to change the pin out of a
2764 (or something similar) to mathc the 1702 socket. 2764s are definitely
easier to find and cheaper than 1702s!
>
>Making up an adapter board shouldn't be hard apart from the fact that the
>1702 doesn't have a ground connection. The simplest way to deal with that
>is to have a flying lead on the adapter board that you solder to a 0V pin
>in the computer. Hardly original, but then nor is using the 2764 in the
>first place.
>
>I suppose you _could_ put a 9V1 zener diode in series with the -9V
>supply to drop the 9V. I'd also connect a 1k resistor between the power
>and ground pins at the EPROM if I did this, to ensure that there's enough
>current flowing for the zener to work correctly. Maybe I'll try it sometime.
>
>> rapidly dropping cost of recordable CDs, I think it whould be worthwhile to
>> record the code on that. They should last nearly forever.
>
>Hmm... I'd rather trust paper tape than a CD. And a paper tape reader is
>going to be a lot easier to repair than a CDROM drive - getting spares
>for those is, in general, non-trivial as I found out. And when was the
>last time you saw a CD-ROM drive service manual?

  Good point but I can BUY a CD drive for less than it would cost me to
move my KSR-33! Actually if you're dealing with a 1702, it's small enough
that you can just write the code down! And paper is paper!

  BTW went to a surplus auction at a nearby air force base yesterday. They
had some of the old familar yellow teletype paper for sale! (Hell no, I
didn't buy it! I would just as soon never see another teletype!)

  Joe
Received on Fri Mar 06 1998 - 22:12:48 GMT