Classic Mac OS Memory Maximising Tricks

When retro Macintosh computers such as the IIci, Performa 475 and even early (beige era) Power Macintoshes were current, RAM was extremely expensive. As a kid trying to push the capabilities of what I had, I sometimes would be in a situation where I just didn’t quite have enough RAM to run a program, for example because the software requires a specific, newer, version of the OS (with a larger footprint).

Today, RAM for these machines is effectively cheaper, but still expensive for some types, hard to find for others (such as the IIx) and lastly, some computers such as the SE or LC have fairly low hard limits.

Choose Your OS Carefully

The most obvious solution is to use an older OS as the further back you go, the less memory the Finder and System tend to use. System 7.1 tends to use around 1 to 1.5MB, while if you’re able to run System 6, requirements plumit into the low hundreds of kylobytes especially if you avoid using the MultiFinder.

If you’re short of memory on a PowerPC, try running a version of Mac OS 7 – the only beige PowerPC that won’t run Mac OS 7 in some form that I know of is the Beige G3. Some machines will even run slightly older versions than the official documentation suggests – for example the 9600 will boot 7.5.3. Note you might need a “System Enabler” for some combinations of computer and OS. These can be found on Macintosh Garden.

Setting up multiple disk partitions or disks, with older and newer supported systems, can be a great way of switching between more feature rich / compatible systems that consume more resources, and smaller, older, more lightweight systems to maximise available RAM.

Optimise

Sometimes you can gain some memory by uninstalling certain software installed in the System Folder. You might consider removing your screensaver, for example.

Suggested things to remove…

• Always remove QuickDraw GX – it isn’t needed and uses a lot of RAM.
• AfterDark or other ScreenSavers.
• Printer Drivers you don’t need (and desktop printing).
• Modem drivers.

Ensuring the hard disk cache size is sensible – if you’re short of memory on a sub 10MB machine, ensure the hard disk cache in the Memory Control Panel is set to 128k or 96k.

If you are using a Power Macintosh, you will often find that enabling 1MB of Virtual Memory in the Memory Control Panel will actually free significant amounts of RAM, especially in Mac OS 8.* and 9.*. Some software refuses to run if Virtual Memory is enabled, other software won’t run without it. Generally, avoid using greater amounts of Virtual Memory – if you really need more RAM, buy more RAM. Real RAM is many times faster than Virtual Memory.

So You Have a II or IIx, or Perhaps a IIfx?

Getting RAM for these machines can be a nightmare, because they need special RAM. “PAL” RAM in the case of the II and IIx (plus complications with respect to ROM versions and memory controllers on the II), and unique form factor RAM for the IIfx.

This is the one and only situation where I would recommend using virtual memory (perhaps also the LC II, Classic II and ColourClassic), but I would specifically recommend the software “RAMDoubler”. Ignore the jeering PC enthusiasts who dismiss this sort of software as snake oil – their platform has a history of scams in this area. The RAMDoubler product is an impressive piece of engineering that attempts to Ballance available RAM, CPU and hard disk. Default settings will give you 100% extra RAM, by compressing the contents of a portion of your RAM. This increases your CPU load, but means the most likely to be reused parts of memory are normal speed while the remaining is still faster than hard disk based virtual RAM. I’m writing from memory, but I believe that the software also performs more agressive memory tidying and may move less frequently used items to disk… But I suggest reading the manual.

At Boot-Time

Another simple solution would could be to boot with shift held down to disable Extensions, but this wouldn’t always work if your program or game required certain extensions to function. Starting up with Extensions disabled reduces the RAM your OS uses to the minimum.

When your software mandates some extensions, you can create and save a minimum extension set using the Extensions Manager. This can be easily accessed by holding space during boot on System 7.5 and later (when it is installed), but it can also be added to earlier versions of System 7, and older versions exists even for System 6.

Extensions Manager allows you to add and remove Extensions and Control Panels and then save “sets”. You can create several, for each of your favourite RAM hungry applications or games. It is also useful for troubleshooting crashes during boot, as it loads early (before most Extensions), loads the interface by holding spacebar, and allows you to remove everything to confirm the OS boots with a minimum config (otherwise the issue is likely the core OS, hard disk or other hardware) add then things back few at a time until you identify what is causing the issue.

Who Needs the Finder Anyway?

The last trick I used to use as a child was to write AppleScripts to quit the Finder and then launch the Application you want. This only works in marginal cases, but has got me out of a hole a few times, including when an Installer application would not launch any other way on a particular machine. Only minimal AppleScript support is required because all applications understand the “open” apple event, but best AppleScript compatibility is with Finder 7.1.2 (so a copy of System 7.1 with Finder 7.1.2 or 7.1.3 installed is a good configuration) or later as this will enable you to do more extensive scripts if you want. A basic script might be as follows :

tell application “Finder”
quit
end tell

tell application “MemoryHog Pro 3.0”
activate
end tell

Save the script as an Application.

To produce a more extensive “Launcher” type AppleScript, you might consider using FaceSpan, which allows you to produce AppleScript based Applets with fancy GUIs using a nice IDE.

Summary

Hope this page is useful to someone. I remember having difficulty getting Escape Velocity to run due to memory restrictions, as well as trying to maximise RAM available for Director 4 (to increase the available Cast size) and for recording sound to RAM.

If anyone has suggestions for what Extensions and Control Panels are memory hogs, or for any other memory saving tips, send me a message via my contact form (under the About drop-down).