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Table of Contents for this issue:
Eudora for 68000 Macs
Re: 32-Bit Clean and MODE32
Re: Performa 405
Re: 32-Bit Clean and MODE32

Subject: Eudora for 68000 Macs

In case you didn't receive it, the November 8 issue of MacUser Web Update included this information on Eudora Light 1.5.5 (fat), which can be downloaded from the address below:

Eudora is a POP3/UUCP application for use with Internet electronic mail accounts. It supports file attachments, MIME and automatic mail checking. This application is a fat binary.

Version 1.5.5 now runs on 68000 Macs, including the Mac Plus, SE, Classic, Portable, and PowerBook 100. 489K.

Subject: Re: 32-Bit Clean and MODE32

So although I've come across references to "Mode 32" in some threads from various items (other newsgroups, and occasionally in a description on shareware), I'm not too sure what it really means. I've also come across the phrase "32 bit clean" and I'm not exactly sure what that was referring to either.

No need to fret. The Classic II has a 68030 w/32 bit clean ROMs and a PMMU which gives you the ability to use Virtual Memory. It does not require (or benefit from in any way) Connectix's Mode 32 to access more RAM. To be safe, if you're using older software and have less than 8 Mbs of RAM installed, let it run in 24 bit.

To keep track of what's where in RAM, the Mac assigns each memory location a unique address. Originally, it used 24-bit addressing, which simply means the addresses could be no more than 24 bits long. In a binary system, that comes out to roughly 16.77 million addresses. But the Mac reserved half of those addresses for other purposes such as tracking information in ROM, et. al. That left only about 8 million addresses for RAM locations-hence, an 8 Mb limit on available memory.

When the Mac was first designed, in the early 1980's, that seemed like plenty, but soon it became clear that Mac developers and Mac users would eventually demand access to more memory. In the late '80's Apple began switching its own ROMs and system software over to 32-bit addressing, urging Mac developers to do likewise. With 32 bits of address information, the available address space jumps to 4 Gb, of which 1 Gb is now set aside for memory.

32-Bit Clean

But the transition raised some problems. The Mac always worked with information organized in blocks 32 bits long, but since only 24 bits were used in memory addresses, developers-including Apple's own software engineers-often used the remaining 8 bits for other kinds of information. If the Mac tried to read all 32 bits as an address, it would be steered in a very wrong direction, and crashes would result.

Software that properly used all 32 bits for addressing is known, in AppleSpeak, as '32-bit clean'. To work in 32-bit mode-to have access to more than 8 Mb of memory-your software (including the software stored in the ROMs of your Mac) must be 32-bit clean. Systems prior to System 7 and the ROMs in most Mac models developed in the 1980's were not 32-bit clean, which is why they couldn't normally handle more than 8 Mb; many applications and utilities from that era were also unclean, which is why they crash if you run them on a newer system using 32-bit addressing.

To preserve compatibility with old software, Apple left 24-bit addressing as the Mac's default mode for several years after it had cleaned up its own act, but it enabled System 7 users with clean ROMs to switch to 32-bit mode via the Memory control panel. By now, however, virtually all current software is 32-bit clean, so switching isn't ordinarily a big problem.

Cleaning Dirty ROMs

Even owners of the Mac II and the SE/30 now have access to more than 8 Mb of RAM, despite their 'dirty' ROMs. The problem was solved first with a free software patch called MODE 32, which was developed by the Connectix Corp. Under pressure from owners of these machines, Apple acquired rights to MODE 32 and began distributing it for free. The company has since released its own equivalent software, called the 32-bit Enabler, but users have reported numerous compatibility problems with it. If you've got an SE/30 or one of those Mac II models, and you need access to more than 8 Mb, MODE 32 remains your best bet. Both programs are widely available from user groups, online services, and savvy dealers.

IBM clone manufacturers and software developers have lately been pretending to have pioneered this technology, as usual. Most lemmings even believe it. Most will also quip: 'Plug & Play' thanks to Microsoft & Windoze 95-WRONG!

Note that 32-bit memory addressing has nothing to do with another kind of 32-bit mode you are likely to hear about and maybe use: 32-bit Color QuickDraw )the 'millions of colors' option available on some Macs), All they have in common are similar names and binary mathematics. (excerpts from The Macintosh Bible, 5th ed., 1994)

which is [now] running System 7.1v3

What is 7.1v3? Was there a 3rd update to 7.1?

Subject: Re: Performa 405
From: Thomas F. Mabry

I would never run anything beyond 7.1 with that small amount of memory. Per GURU you can upgrade with 12meg of memory but only a maximum of 10meg can be addressed by that machine. The cheapest upgrade that you could do to get more use out of that machine would be to add memory. At 10meg a stripped down version of 7.5 would be workable. The real trick to getting full use out of an old Mac is to not ask it to do more than it was really intended to do. Good Luck....

Thanks for the tip. I think that I can try to run 10 megs and a stripped down version of 7.5. How do you think Ram Doubler would assist in the memory situation?

Again, thanks . . . the machine presently has System 7.1 P2 on it and I have never heard of that system.

Take care . . .

Tom Mabry

Subject: Portables
From: E. Barnes

How nice to connect with others who love the old yet workable Macs.

If anyone else has a Portable (my steady b/u to my PowerMac) and needs the full 9Mb or RAM of which it's capable and/or a larger HD than the original 40Mb Connor, I've found a neat company in California to do the upgrade. They're called Dynamic Computing in Ben Lomond, CA (between San Jose and Santa Cruz), and Jackie may be reached at 408/336 8891.

Good service, great people.


Subject: Re: 32-Bit Clean and MODE32
From: System Administrator

So although I've come across references to "Mode 32" in some threads from various items (other newsgroups, and occasionally in a description on shareware), I'm not too sure what it really means. I've also come across the phrase "32 bit clean" and I'm not exactly sure what that was referring to either.

By a coincidence I had just explained this very question to someone else, in answer to a slightly different question. Here's an extract from my message (talking about the "Memory" control panel):

The "32-bit memory" option relates to an historical issue with 680x0 addressing... here's time for another history lesson 8-) All 680x0 chips have 32-bit internal registers. But the 68000 and 68010 have only 24 address pins (I think simply due to the fact that they wanted to get these chips into a 68-pin package). This means that the upper 8 bits of any address value are stored faithfully, but ignored by those chips. The 32-bit memory option simply specifies whether or not MacOS will allow applications to access memory which requires those extra 8 bits. Some insane applications (and even the ROMs on some early Macs, up to and including the SE/30) actually used those upper 8 bits to store additional information. No problem on the 68000 and 010 where those bits were ignored, but big problem on the 020+ where they are expected to contain valid address information.

"32-bit clean" means that the code does NOT make "illegal" use of the upper 8 bits of address registers.

MODE32 is an INIT (by Connectix I think) which patches around some of the non-32-bit-clean stuff in older Mac ROMs. It is not necessary for modern Macs (modern being any of the LC series, Color Classic etc).

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