For a number of reasons, it's worth the effort to modify the board to accept,
say, a 2716, which is a single-voltage part 8x as large in capacity, though the
same physical size. First of all, it makes it easier to write meaningful code,
as 256 bytes is a pretty cramped space in which to store a control program.
Second, as you've already discovered, it's difficult to get the 1702's
programmed, and, third, you've probably checked the prices of these parts. I'd
not expend the effort in favor of 2708's or other multi-supply parts, since
these are more difficult to program than the single-voltage parts.
If there exist more than one 24-pin socket, it would be worth the effort to
modify the board to accept a 6116 SRAM as well. The extra RAM will not hurt
either.
If you're into saving the authentic configuration, however, you have a
completely different set of problems. Not only do you have to deal with the
cost of the devices, but you have to figure out how to program them. I'm not at
all sure, but I may have an old (1976 or so) Intel databook that describes how
to program the parts. It may take a few days to find it, though.
Dick
----- Original Message -----
From: "Glenn Roberts" <groberts_at_mitre.org>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, April 13, 2001 5:13 AM
Subject: 1702A EPROM Programming
> I've been working with someone who has an old 8080-based single board
> computer he's trying to get to work. We're investigating several
> possible problems but it's starting to look like there's a problem with
> the EPROM. I have the ROM code he needs and will be checking out the
> EPROMS, but we may be faced with a need to reprogram one or both of
> these. They're the old 256 byte 1702A Intel chips (ceramic). I've only
> programmed the 27xx series but have read that the 1702's are "really
> difficult" to program. Was wondering if folks in this group could
> comment on how to proceed if/when we decide we need to reprogram one of
> these. Are there more modern plug compatible alternatives? We may also
> need to replace one or both - any sources known other than eBay?
> thanks.
>
> p.s. FYI, the computer here is the "MMD-1", an old 8080
> trainer/breadboarding box. here's a picture i found on the web:
>
> http://online.sfsu.edu/~hl/c.E&L-MMD1.html
>
>
> - glenn
Received on Fri Apr 13 2001 - 10:11:07 BST