In general, software written for a Mac will run on virtually any Mac,
provided you have enough hard disk space and enough RAM (and a CD-ROM
drive, if the software comes on a CD!).
Here are some exceptions that you may want to be aware of.
Don't be fooled by the length of the list;
it isn't really very restrictive.
- The two earliest models, the 128K Mac and the 512K "fat" Mac, have
too little RAM for anything but dawn-of-time software, and you cannot add more;
they have no SCSI port, therefore virtually no upgrade is possible.
- Some programs, especially state-of-the-art games on CD-ROM, require a
640x480 (or larger) color monitor, and very old Macs don't support such
- With the release of System 7.5.5 (October 1996), Apple stated
that this would be the last system software release for the
Macintosh Plus, SE, Classic, Portable, PowerBook 100, SE FDHD,
SE/30, LC, II, IIx, and IIcx. These are very old computers that
do not support 32-bit addressing.
- Most modern programs expect to be installed onto your hard disk.
(Even programs on CD frequently expect to put a few things on your hard disk.)
You need to have a hard disk with a reasonable amount of space available.
- Every program needs a certain minimum amount of RAM to run, and every
Macintosh model has a limit on the amount of RAM that can be installed.
While many programs continue to work fine (even with only 4 MB of RAM),
very large programs may require more RAM than it is possible to put on a
particular Mac. Microsoft and Netscape are the worst offenders in this area.
- Some number-crunching programs require an FPU (floating-point unit) to run, and some Macs don't have an FPU. However, there is a shareware program
(Software FPU) that will allow most of these programs to run, albeit slowly.
- Apple began switching over from 680x0 Macs to PowerPC Macs in 1994. While it is generally easy to make "fat" applications that run on both 680x0 and PowerPC Macs, some new software is PowerPC only (mostly because it depends on the speed of the newer Macs). This situation will slowly get worse.
- From the very beginning, Apple has published guidelines on how to write
software that will continue to work on newer machines. While most companies
have followed these guidelines (Apple itself and Microsoft being notorious
exceptions), some shareware authors have not done so. If there is a
particular piece of software that you need to be able to run, you
should if at all possible test it on the machine that you intend to buy.
Note that the Mac Plus (only the third Mac ever made) can go up to 4 MB of RAM and has a SCSI port. This will run even the current System, 7.5.5 (but you probably want to drop back to System 6 to make more RAM available). Since the current market value of a Mac Plus is approximately zero, boosting one to 4 MB of RAM and putting WriteNow on it is probably the cheapest way to get a machine that will let you do serious work.
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