wack@UDEL.EDU.UUCP (10/02/87)
>Is there an EPROM that will directly replace the ROM's >in the Apple II+? I mean really, just program and plug in? >I tried 2516/2716, but the chip select logic is not the same. >Anyone know? How about the IIe? Do they use the same >ROM chip? > > Doug Plate The easy question first: You can use a 2764 to make a replacement for the //e's roms. (These are the program roms marked CD and EF on the motherboard not the character generator or keyboard roms, they can be replaced by 2732 and 2716 eproms respectively). One cavaet to this is that I believe (all though I'm not 100% sure) that the newer //e with the numeric keypad has only a single rom chip which would be a 27128 in that case. (IIgs fans you need a 271024 to replace your rom chip!!) For the II+ things get more difficult. There are two choices. The first is to find a company that makes a special socket to adapt a 2716 to the II+. One such device that I have is called a "Promette" from Computer Micro Works in Dayton OH. I don't know if they are still in buisness. The second choice will make all the EEs reading this cringe, but it works. Burn the 2716 as usual, then being very careful, bend up pins 18 and 21 so that they won't touch the socket when inserted. Then solder a wire connecting pins 21 and 24 and a second wire between pins 18 and 20. This should allow the 2716 to work properly in the II+. The only problem with this mod is that it keeps the chip enabled at all times. So if you have a 16K expansion card and it is activated and you get a request for an address in the rom space, both the ram card and the rom will try to supply data. This is what EEs call buss contention. Fortunately the ram card wins out with most eproms I have tried (AMD seem to be best) so everything works as it should. It worked for my II+ for 6 years until I retired it in favor of a gs, and the II+ still runs fine so it doesn't seem to hurt anything. (All EEs please hold your hate mail) If you don't like the idea of altering the chip, you can do the same procedure to a socket, then plug the chip into the socket, and then plug the whole thing into your motherboard rom socket. (Machine pin sockets work best although they tend to ruin the motherboard sockets when you force them in) Andrew Wack --- ARPA: wack@udel.edu short .sig!