Most of these older fused PROMs are of comparable speed in newer EPROMs or E2PROMs. Open collector is a hassle but not too much. One can create the needed circuits using surface mount parts for size reduction. A hassle but not out of the question. You usually have to go to a larger ROM size so it can be used for additional storage with a switch or jumper select. Dwight
________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Brian Marstella via cctalk <cctalk@classiccmp.org> Sent: Monday, September 27, 2021 9:16 AM To: Jay West <jw...@classiccmp.org>; General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> Subject: Re: Programming Bipolar PROMs I recently picked up an EPROM+ programming unit ( https://www.arlabs.com/eprom_plus.html) from eBay used in order to program a couple of PROMs. Unfortunately, I haven't actually tried it yet but the 82S23 and others are supported. The owner of the company seems to be extremely responsive to any and all questions and has a lot of documentation on the web site. On Mon, Sep 27, 2021 at 11:48 AM jwest--- via cctalk <cctalk@classiccmp.org> wrote: > Jon wrote... > I can do them with the Data I/O 29B and UniPak 2B. Some of the other > UniPaks can handle them too. They are one of those devices that most of the > newer commercial programmers can't do. I wouldn't call the Data I/O really > affordable, though. > ------ > Same, I use a data i/o 29B for these. Jon is right, the 29B seems to have > held significant value $-wise still on ebay. But you can find a reasonable > deal once in a while. > > And.... > Watch out buying blanks on eBay, they're often pulls and are actually > already programmed. Also the yield was not 100% even back in the day, > apparently, so buy several to ensure you do get a good one. > ------ > I gave up trying to find any quantities of the 3 or 4 different bipolar > proms used for the HP 2100/21MX line on ebay. I had significant luck > contacting arcade game repair houses, and got a reasonable quantity of most > all the flavors I needed. I checked back a couple years ago and all the > usual arcade places no longer had them ☹ > > I do believe I saw a writeup on the web somewhere where someone took a > different chip and programmed it to act like a (now) rare bipolar prom. I > don't recall how successful it was - I'd imagine the speed of the bipolars > would be an issue, plus ISTR height was an issue too (new chip was on a > carrier of sorts, creating headroom issues on some systems). > > J > > >