Steve Q wrote: > I've got a ROM 00 "Woz Limited Edition" boat anchor that I picked up cheaply > some time ago. I got on the horn with AllTech a few days ago and asked > about the ROM 01 upgrade that they've been known to carry, and I was lucky > enough to hear "We have one left." OK, it's on its way to me, and at least > I'll be able to boot GS/OS on this thing. > > My question is this: > > I'm not much of an electronics person, but a good friend -is.- Let's say > that I'd like to copy these ROM 01 upgrade chips, so that if I'm ever in > this predicament again, I can simply roll my own (and for personal use...I'm > certainly not looking to pee on anybody's lawyers or anything like that). > Is this doable? It is difficult, because the IIgs uses a type of mask programmed ROM which holds 128 KB in a 28 pin chip. Standard 128 KB EPROMs are 32 pin chips, so they don't fit on the IIgs motherboard unless you build a socket adaptor. The ROM 3 motherboard has provision for installing 32 pin EPROMs, and this was used in prototypes and some early production machines. There may be a rare type of 28 pin 128 KB EPROM, but I haven't heard of any such chip. The problem is that the 28 pins are completely occupied by the address bus, data bus, power, ground and a single chip select signal. An EPROM also needs a programming voltage input, so a 28 pin 128 KB EPROM would need to supply the programming voltage through the Vcc input (normally +5V). Most modern EPROMs use +6V or +6.25V on this pin during programming, and need +12V or thereabouts on a separate Vpp pin. > PS: Is there any way to identify a ROM 00 versus a ROM 01 versus a ROM 03 > simply by looking at the case (assuming motherboards haven't been > transplanted)? The only visible external difference would be the serial number, and I don't know what ranges apply to each machine (there may be some overlap). The cases are identical, apart from the "Woz limited edition" which is printed on early machines (all of which were originally ROM 00, but might have been upgraded to ROM 1). The motherboards are interchangeable. The best solution is to pop the lid and look at the motherboard. The ROM 3 has several obvious differences from ROM 00/01, the main one being that it has two ROM chips instead of one. One other point mentioned by other people in this thread is the video chip which was typically upgraded as part of the ROM 00 to ROM 01. This is the VGC (Video Graphics Controller), which is a socketed PLCC (square pack), so assuming you can get the replacement, you will need a PLCC extractor tool to replace it. Early versions of this chip had an error which caused them to display flickering pixels (usually pink) when displaying monochrome double hi-res graphics mode, and some also displayed them in 80-column text mode. The replacement VGC fixes the problem. This problem is purely cosmetic - if you can't get an upgraded, the machine will work fine, but will look strange when displaying the affected video modes. If I remember right, the VGC version affected by this fault has a part number which ends in either -A or -1. Later revisions (-2, -3, -B and -C) are OK. -- David Empson dempson@actrix.gen.nz "Steve Q" wrote: >I'm not much of an electronics person, but a good friend -is.- Let's say >that I'd like to copy these ROM 01 upgrade chips, so that if I'm ever in >this predicament again, I can simply roll my own (and for personal use...I'm From what I recall of past discussions, it wouldn't be possible due to the lack of existence of an EPROM being available in the needed pin package/memory size (128K, but in a 28-pin DIP). You'd need to rig up a socket adapter, and to this day, I've never heard of it being done. Your best bet is just keeping a ROM 0 as-is (some people seek these just as an obscure collection piece) and simply pick up a base ROM 01 box or motherboard. They're generally $5 or less these days--I even saw some sell on eBay for 1 cent recently! >certainly not looking to pee on anybody's lawyers or anything like that). Incidentally, Apple stopped offering the free ROM upgrade as of March 31, 1995 and it's undoubtedly not available any longer even as a special part order (Apple released a press release several years back saying they were no longer obligated to carry parts or do repairs to products less recent than the mid/late 90's). For that reason I doubt even Apple would object to you burning your own ROMs for upgrade purposes (obviously to systems you already own). Assuming you found a way to do it... >PS: Is there any way to identify a ROM 00 versus a ROM 01 versus a ROM 03 >simply by looking at the case (assuming motherboards haven't been >transplanted)? If the case is closed (and sealed with that screw in the back-middle) you could look at the serial number on the bottom of the case. It's not an infallible method however, the oldest IIgs motherboard fits perfectly in the newest IIgs case (and visa-versa). If a dealer or user ever did a ROM or motherboard swap, case markings are meaningless. Assuming you do come across an unaltered system from the day it was bought, you can use this serial range to help guide you: - earliest <------------------- ROM 00 + faulty VGC - ....etc - 703xxxxxx - 704xxxxxx --------------------------------------------------------- - 705xxxxxx <--------------------ROM 00 - 706xxxxxx - ....etc - 723xxxxxx - 724xxxxxx ---------------------------------------------------------- - 725xxxxxx <------------------- ROM 01 - 726xxxxxx -.....etc Off hand I don't know the serial number range for the ROM 3, and all IIgs cases had the same model number regardless of which motherboard was in the case (A2S6000). My ROM 3, from early 1990, starts with this number if it helps: "013xxxxx". The IIgs I bought in late 1987 started with "815xxxx". >The classic method is to boot the system, but once in >awhile, I find systems that are sold by organizations that won't let you >fire them up inside the place (even though they allow returns). I'd guess >that the answer is "No," other than maybe looking for "1989" on the ROM 03, >but in case someone knows a trick I don't know, I'd love to hear it. Thanks >again. The best way to tell is opening the case and looking inside. I can instantly spot a ROM 00, 01 or 3 motherboard, even glancing at a fuzzy photo image. ROM 00 motherboard: - White sticker on ROM chip - ROM part number suffix is "-A" , and "86" is last copyrighted year ROM 01 motherboard: - Part number silked-screened on ROM chip (no sticker) - ROM part number suffix is "-B", and "87" is last copyrighted year ROM 3 motherboard: - Two ROM chips side by side (instead of one) - Eight RAM chips (instead of four) - Battery in snap-case, next to slot-1 (visible with powersupply installed) - 'Sound RAM' and 'Standard RAM' arranged in a straight line - "Apple IIGS" printed vertically on right (instead of "//GS" horizontally) - Ensoniq and VGC chip soldered directly to motherboard (no socket) - Slots labeled "J1", "J2", etc in small print (not large plain numbers) - Board color a darker green (in some cases, with gold colored pathways) I could go on (i.e. CYA, newer ADB microcontroller, 'S1' jumper pins, manufacturing date codes and so on) but once you spot the first two or three visual signs above, you'll already know it's a ROM 3 board (well, technically "The Apple IIGS with 1 Megabyte of RAM" board as Apple officially named it). As a side note to the above, there really is no such thing as a ROM '00' and '01' motherboard. Only one board was produced (with 256K RAM installed) and you could plug either ROM chip into it. Also, all three firmware revisions came as masked ROMs (the only exception was an early leaked beta copy of the ROM 3 which came on a pair of EPROMs). Hmm,, speaking of that, did anyone ever confirm whether there had been a second leaked version of the ROM 3 firmware? Several months back someone mentioned having EPROMs with 341-xxxx part numbers never before heard of. Mitchell Spector a_specto@alcor.concordia.ca