Fantastic advice. I'm glad you brought up the latter.
What do you know about the Portable's Max. RAM capability?
This came up with Paul Pratt's Mini vMac as he informs me the 100's ROM is located at 0x900000, suggesting 9MB is the top limit for the 100 anyway, which is supposed to be identical to the Portable according to Apple.
I've also seen reference to the Portable being able to use 10MB RAM. If it is truly identical to the 100 ROM, theoretically the 100 could use 10MB as well, though Paul's revelation on the ROM memory address would indicate 9MB as the top configuration.
Apple may clear it up with this TIL: http://docs.info.apple.com/article.html?artnum=14870
It indicates the original Portable with 1MB and an 8MB card could reach 9MB. The backlight Portable and 100 though can only accommodate up to 8MB. Which is odd because the Backlit Portable still only has 1MB base RAM meaning it would need an odd 7MB RAM card to reach 8MB. Given that the ROM can support up to 9MB RAM based on address, I would think at a minimum adding an 8MB RAM card to either (the lack of one might be the reason the 100 never exceeded the 8MB limit), would push it to 9MB & 10MB respectively, though only the first 9MB would be accessible.
This may shed some info on the Portable differences:
http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-68K_Portable/Portable_BackLit.pdf
This article seems to indicate the 9MB is achieved in the Portable via the PDS slot which the 100 does not have. However, that does not explain why the backlit Portable would be limited to only 8MB.
http://docs.info.apple.com/article.html?artnum=10199
I see what you mean about prices!
http://www.edgetechcorp.com/memory/upgrade.asp?cid=15553
Also, is it possible to upgrade the 100's screen to an active matrix one? Or is that specific to the LB video driver,not the LCD?
Tom, is the 180 compatible? If it has 14MB, does that mean It has a 10MB module? Is that RAM card compatible with the 100 and can the extra RAM be removed and re-soldered to fit? How about the 190, or is that closer related to the 520?
Also, I read somewhere that the 100 uses Duo-type RAM and as such is that compatible or does it require a custom card for the 100?