Unique Japanese Mac Plus ROM?

[Daxeria]

From Tech Note #138:


The Japanese Macintosh Plus has the Kanji 12 and 18 point fonts in ROM [...] Note that the Japanese Macintosh is unique; Apple has not produced other foreign versions of the Macintosh for different scripts. The introduction of the Arabic Interface System, for example, did not include an Arabic ROM version.



Has this ROM variant ever been dumped?

 

[Paralel]

Good question. From a quick look around, not that I can tell.

 

[Dog Cow]

 From a quick look around, not that I can tell.

Did you check the Japanese Mac sites too in your quick look? The Japanese are big classic Mac fans, and they will certainly have access to a JP Plus ROM.

 

[Paralel]

Nope. My Japanese isn't strong enough to parse out the proper search phrasing, and I wouldn't trust an auto-translator.

 

[trag]

That's interesting because one of the early HW tech notes from Apple claims that there are only 3 revisions of the Mac Plus ROMs, Lonely Hearts, Lonely Heifers, and Loud Harmonica.   And the latter two revisions only changed 2 and 32 bytes of code to fix SCSI edge cases. 

I wonder if the documenters were not well hooked into what was going on with international models.

View attachment hw_11.pdf

 

[Dog Cow]

That's interesting because one of the early HW tech notes from Apple claims that there are only 3 revisions of the Mac Plus ROMs,

A tech note that is most likely intended to apply only to the standard, canonical Mac Plus ROM.

I wonder if the documenters were not well hooked into what was going on with international models.

That's probably not the case. More likely is that they were documenting the standard, canonical ROM in the earlier tech note. Look at Tech Note #138, the genesis of this thread. Obviously that was documentation.

 

[trag]

Ah.  Thank you for pointing that out.   I was looking at "new content", but somehow, I never saw the first posting.

 

[Dandu]

Hi. I have dumped the japanese ROM and the 12 pts fonts was in there https://www.journaldulapin.com/2025...f-the-macintosh-plus-which-isnt-lost-anymore/

 

[Frobozz]

That’s great. Thanks for write up. I used kanjitalk a lot back in the day but that what’s for system 7 and then 7.5.5 (or so). I still have my KT disk installers somewhere. 27ish disks. Weee!

Its interest to me that the kanji don’t in this early version looks a lot more like the typical JA fonts you would find on Japanese computers of the day and less like what JA fonts looked like on the later kanjitalk OSes. I think Japanese computer designers maximized the use of available space whereas Apple used up less of it. It might have looked better (to a Western viewer) but one complaint Japanese people always gave me about the Mac was that the fonts were too small and hard to read.

 

[Andy]

Wow that's really cool! Thanks for making those videos, it really shows what a difference the extra ROM makes. What a painful amount of disk swapping without.

With the custom chip pin out, will they work in a standard Plus logic board? Or is it a custom version?

 

[David Cook]

Hi. I have dumped the japanese ROM and the 12 pts fonts was in there https://www.journaldulapin.com/2025...f-the-macintosh-plus-which-isnt-lost-anymore/

That is amazing! Great write up. I never would have believed this was going to get found. @JDW would very much like to know about it.

 

[Dandu]

Wow that's really cool! Thanks for making those videos, it really shows what a difference the extra ROM makes. What a painful amount of disk swapping without.

With the custom chip pin out, will they work in a standard Plus logic board? Or is it a custom version?

Yep, it works on a classic Macintosh Plus board

 

[dougg3]

Excellent write-up! The disk swapping that was required at startup without the Japanese ROM was crazy and really shows why they did this. Thanks for dumping this ROM and sharing it with the community! It's funny how people have dumped it in the past and claimed it was the same as the v2 -- they were right, it's just the full chip didn't get dumped.

I find it interesting that Apple's tech note claimed the 18pt font was also in the Japanese Plus's ROM, but unless I'm missing something, it seems pretty clear that it wasn't. It still asks for the 18pt disk, and additionally, the 18pt font file on the disk is 244 KB. The ROM would have to be doubled in size again (to 512 KB) in order to hold the 18pt font. I guess if somehow those chips are actually double the size we think they are, the 18pt font could be hiding in the second half, but based on bbraun's pinout you linked, I don't see any additional address lines that would make it possible. Plus, like you pointed out in the article, the chip markings seem to indicate that the chips are 1024-kilobit each, for a total of 128 KB + 128 KB = 256 KB.

 

[adespoton]

Awesome; I'll get https://docs.google.com/spreadsheets/d/1wB2HnysPp63fezUzfgpk0JX_b7bXvmAg6-Dk7QDyKPY/ updated and get the ROM details added to https://github.com/sentient06/MacROMan/ as soon as I can (not quite sure when that'll be).

 

[Dandu]

There is a mini vMac fork with support : a modified version on GitHub

And i have added the ROM "combined" to the archive (it's interleaved)