Why System 6 for Compact Macs?
Manuel Mejia Jr - 1999.11.26
Q: What is System 6, and why is it the preferred system for compact Macs?
A: System 6 was the operating system used by all front line Macs from 1989-1991. It came out in a variety of versions from 6.0 to 6.08L. It is considered the optimal system for the compact Macs like the Mac Plus because it can run in as little as 500K of memory. System 6 can also be loaded onto an 800K floppy with enough room to hold an application program and allied files.
Back in the late 1980s, the standard Mac Plus had only 1 MB of memory, no hard disk, and a single 800k floppy. Just about all that was needed in terms of software had to be packed into that one floppy disk. As a consequence, System 6 had to be compact. While one could get a hard drive, that would drive the price of Mac up significantly ($500-1,000). The big advantage to having the hard drive is that one could store System 6, applications, and allied files without having to use floppy disks. It was also faster.
System 6 is very modular. The System and Finder are the two main items needed to operate the Mac. To increase the variety of features, such as additional fonts and Desk Accessories (DAs), one used a program called Font/DA Mover. This piece of software installed fonts like San Francisco, London, and New York, as well as DAs like Key Caps, Calculator, Scrapbook, and SuperClock. When the Mac user was finished configuring the System with the fonts and DAs, Font/DA mover could be deleted without impacting the Mac's operation.
By designing System 6 in this modular manner, Apple was able to create a functioning operating system that could run in as little as 450K of memory. The remaining 550 K of memory on a 1 MB machine could be used for programs like MacPaint, MacWrite, or PowerPoint 1.0. All of these programs could be run using 375-500k of memory. The end result - a fully functional computer running with only 1 MB of memory!
If one chose to upgrade the standard Mac Plus or SE to 2, 2.5, or even 4 MB of memory, larger programs like Microsoft Works 2.0 (728K) could run.
Later OS versions, like System 7, need much more memory to operate, about 1.2 MB minimum. System 7 needs 2 MB as a minimum for the operating system and a small program. It was also not practical to run System 7 off a floppy because of the size of the OS and limited size of the floppy disk.
For the simple Macs like the Plus, SE, or Classic, a memory upgrade was needed for System 7, as well as a hard disk. Another issue is computer speed. System 7 slowed down the Mac Plus significantly, because it always ran in "MultiFinder" mode. (System 6 normally ran as a single application operating system, but MultiFinder allowed the user to have more than one program open at a time.)
Because of all this, System 6 is still popular among classic Mac users, even though other software that was meant to replace it has come and gone.
Manuel Mejia Jr is familiar with Mac IIs, LCs, and older PowerBooks. He uses his Mac LC, PowerBook 145B, and PB 100 with System 7.1 on a regular basis and recently added a Mac Plus running System 6 to his collection. He's quite familiar with both System 6 and System 7. He also owns the Pina books on repairing compact Macs from 128k through the SE. You can read more about Manuel's computers in Manuel Mejia Jr's Four Old Macs.
Not sure if you should upgrade your old Mac or replace it? Check the Mac Daniel index to see if we've already addressed your problem.
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