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128K floppy drives and Version A ROMS


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This topic came up in a thread that started as a conquest two years ago (I was crowing about finding a 128K mac in good shape that I was having trouble starting from the floppy drive) and turned into a longish thread on floppy drive compatibility. As I just posted in an update to that thread, I think I finally tracked down the problem, with the help of advice from @BadGoldEagle that I should have paid closer attention to in the first place. I wanted to provide a few links for anyone who might be struggling with this problem and searching for an answer.

 

tl;dr version: I finally worked out that the floppy drive which came to me installed inside the otherwise untouched 128K with Version A ROMs is an incompatible type that only works with Version B ROMs or later. (This thread has more extensive discussion of this type of problem and links - the whole thread is relevant but scroll down a bit for the incompatible floppy drive discussion.) The symptom of the incompatibility is that the drive seems to work occasionally but throws all manner of mysterious errors and sad mac codes. Mysteriously, the drive chassis has a February 1984 sticker. All I can think is that someone tried to replace the stepper motor at some point and didn't realize that they type they were using was incompatible. I didn't think the new stepper motor was used until at least summer 1984.

 

Here is the start of the 128K saga in my longer hoard thread. (I need to make some additions to the hoard, I have a Wallstreet now...)

 

I guess I could fix my own problem by upgrading to a later version of 64K ROM but I kind of like my original ROMs. I'll have to quest for an early compatible 400K drive with the round sticker.

 

Hope this helps someone!

 

 

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Nice. Keep the rev A ROMs, obviously. Thanks for pointing to that 2016 thread. I knew about the three different Macintosh Plus 128k ROMs, but not about the revision of the 64k ROMs in the 128K/512K -- which makes perfect sense. I gather the switch from rev A to rev B occurred in August 1984 about the same time as the 512K went into production and they started using the dual-use motherboard. I think I should provide those part numbers on my site, as well as those for the Macintosh Plus ROMs.

 

Is there actual evidence of a rev C for the 64k ROMs, or is that an assumption based on the wording of that Apple Support article on the floppy drives: "One of them is compatible with any rev of ROM on the Macintosh. The other is not compatible with revision A. It is only compatible with revisions B or later." I think that "or later" could have been future-proofing, and not necessarily indicative of the existence of a third revision.

 

Here's what I have so far:

 

64k rev A: 342-0220-A and 342-0221-A ©APPLE 83

64k rev B: 342-0220-B and 342-0221-B ©APPLE 84 (still in production as of late March 1985 at least)

 

128k rev A:

128k rev B:

128k rev C:

Edited by Rasmus
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It's amazing. All of this was discussed and discovered on these very forums over a decade ago. But it appears the search function for the archive of posts from that time has been disabled? I guess I've been gone too long. Sad that so much useful information has to be rediscovered. But then, that's half the fun, no?

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On 6/10/2018 at 2:11 PM, Mac128 said:

It's amazing. All of this was discussed and discovered on these very forums over a decade ago. But it appears the search function for the archive of posts from that time has been disabled? I guess I've been gone too long. Sad that so much useful information has to be rediscovered. But then, that's half the fun, no?

Ha ha, yes! The sorry part is I may well have been involved in those threads! Technical details like this tend to flee the memory. I'm about to post a whole series of questions/mysteries/theories about the early Mac Software disks, and I keep getting this sense of deja vu as I pull it together...

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  • 1 year later...

Hi to all, I'm new to this forum. I bought a broken M0001 128K 120V USA and my challenge is to get it working again.

After repairing the Analog Board and changing a bad RAM (it was exciting for me to see again an happy mac) my next obstacle was the missing floppy drive. I've found one on ebay, but despite of the model (OA-D34V), it has a rectangular label on stepper motor so I have no chance to get working with my couple of (A) ROMs. Finding a couple of (B) ROMS was not so easy or expensive. I have a couple of new 27C256 OTP in my box and I would try to burn them with the 42-0220-B and 342-0221-B binary but I was not able to find the correct files. Can someone tell me if is there a link where to download them? Thank you in advance 

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23 hours ago, zemagi said:

Hi to all, I'm new to this forum. I bought a broken M0001 128K 120V USA and my challenge is to get it working again.

After repairing the Analog Board and changing a bad RAM (it was exciting for me to see again an happy mac) my next obstacle was the missing floppy drive. I've found one on ebay, but despite of the model (OA-D34V), it has a rectangular label on stepper motor so I have no chance to get working with my couple of (A) ROMs. Finding a couple of (B) ROMS was not so easy or expensive. I have a couple of new 27C256 OTP in my box and I would try to burn them with the 42-0220-B and 342-0221-B binary but I was not able to find the correct files. Can someone tell me if is there a link where to download them? Thank you in advance 

OK, I've found the full rom image at https://www.macintoshrepository.org/7038-all-macintosh-roms-68k-ppc- . Now, there is a very useful tool https://github.com/freem/romwak written in ansi C, so  it can be compiled in OS X too.  With it have split the 64k rom image file "1984-10 - 28BA4E50 - Macintosh 512K.ROM" to two 32k Hi and low files with the command "romwak /b file_orig file_hi file_low" next week I'll burn the EEPROMs and I hope it works. Then I'll post the ROM images for you. 

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