Article 179870 of comp.sys.apple2: Newsgroups: comp.sys.apple2 Subject: Re: ROMs for IIgs References: <3B705C45.A02A1249@intergate.bc.ca> X-Newsreader: NN version 6.5.6 (NOV) From: david@uow.edu.au (David Wilson) NNTP-Posting-Host: wraith.cs.uow.edu.au Message-ID: <3b70a762$1@news.uow.edu.au> Date: 8 Aug 2001 12:43:46 +1000 X-Trace: news.uow.edu.au 997238626 wraith.cs.uow.edu.au (8 Aug 2001 12:43:46 +1000) Organization: University of Wollongong Lines: 97 Path: news1.icaen!avalon.net!norand.com!newsfeed.media.kyoto-u.ac.jp!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!news1.optus.net.au!optus!news.usyd.edu.au!news.newcastle.edu.au!news.uow.edu.au!david Xref: news1.icaen comp.sys.apple2:179870 Wayne Stewart writes: >Andrew Trotman wrote: >> I've searched the web and it appears that no-one sells ROM 03 for the IIgs >> and it isn't possible to burn it into an EPROM either as 28pin EPROMs don't >> exist >> >> It this right? >> >> Andrew. The reason no one sells the ROM03 is that it only works in the 1MB IIgs motherboard (it is two chips) and they all came with one installed. The 256KB IIgs motherboard came with either a single ROM00 or ROM01 chip and can not be upgraded. The only ROM03 chips not in motherboards would be spare parts from Apple but we may have passed the period Apple keeps spares for discontinued IIgs computers. >If you look at the front of those 28 pin sockets you'll see that the >motherboard was >designed to take either 28 or 32 pin sockets. The 32 was in case Apple decided >to >use EPROMS , which they did sometimes. While changing the socket'd be a pain, >adding a couple of pins to the end wouldn't be difficult. The number on the >EPROMs >I have are M5M27C100K-15. I don't have the means to get individual ROM images >but I can send you a collective ROM image of the two if you can work with >that. If not >I can likely scare you up a set of ROMs but it'd have to wait till I next dig >into my >storage which may be a while. > Wayne The only problem with using 32 pin EPROMs in a //gs, even if it has 32pin sockets is that the pinouts of the ROMs are not quite the same as those of EPROMs. 1Mb/128KB EPROM 1Mb/128KB ROM ---------------- ------------- 1 Vpp -- 2 A16 -- 3 A15 1 A15 4 A12 2 A12 5 A7 3 A7 6 A6 4 A6 7 A5 5 A5 8 A4 6 A4 9 A3 7 A3 10 A2 8 A2 11 A1 9 A1 12 A0 10 A0 13 D0 11 D0 14 D1 12 D1 15 D2 13 D2 16 GND 14 GND 17 D3 15 D3 18 D4 16 D4 19 D5 17 D5 20 D6 18 D6 21 D7 19 D7 22 /CE 20 /CE 23 A10 21 A10 24 /OE 22 A16 25 A11 23 A11 26 A9 24 A9 27 A8 25 A8 28 A13 26 A13 29 A14 27 A14 30 --- 28 VCC 31 /PGM -- 32 VCC -- As you can see, all the pins match up EXCEPT pin 24/22. On the Apple ROM it is A16 while on the EPROM it is /OE and A16 has moved to pin 2. If you look at the circuit diagrams in the back of the IIgs hardware reference manual (1st edition) the signal is even called ROMOE/A16 or something similar. Does the ROM03 have a jumper to relocate the A16 signal? There may be a 28 pin 128KB EPROM (the same problem occured at the transition from 24 pin 2732 (4KB) to 28 pin 2764 (8KB) - Motorola had a 24 pin 68764 (8KB) which managed to make the /CE pin do double duty as an enable and as the VPP pin when programming) but I do not know its part number or manufacturer. An adapter can be constructed out of a 28 pin plug and a 32 pin socket: plug socket 1..21 3..23 22 2 A16 23..27 25..29 28 32 VCC 22+24 common /OE with /CE 1+31+32 common VPP and /PGM with VCC (I think - check this with EPROM data sheet (271001). 30 leave open or connect to VCC -- David Wilson School of IT & CS, Uni of Wollongong, Australia