In January of 1994, Connectix introduced RAM Doubler, an innovative utility that transparently appeared to double the amount of memory in most Macs (it requires a 68030 processor or higher). I was impressed with it back then (see TidBITS-208 for a review and more information on how it works), and now that Connectix has released a major update, RAM Doubler 2, I remain impressed.
Over the years, Connectix has released a number of free updates to RAM Doubler 1.x, mostly to fix bugs or ensure compatibility with new Macs and new releases of the system software. Since RAM Doubler works at a very low level, hardware or system software changes can break it more easily than other programs. But, as I said, these updates were all free and available on the Internet, so downloading updates wasn't a problem for most people.
New and Cool -- In August of 1996, Connectix released RAM Doubler 2, which provided several major changes.
Though there were some hacks that could change this capability, RAM Doubler 1.x could only double your memory. RAM Doubler 2, in contrast, has a control panel interface that enables you to set how much memory you want to end up with, ranging from nothing extra (more on why you might want to do that in a minute) to three times the amount of real RAM that you have installed. You can multiply your existing real RAM by 1, 1.5, 2, 2.5, or 3 times, and by intermediate values if you press Option while moving the slider bar.
The first version of RAM Doubler had no interface: you simply installed it and rebooted. RAM Doubler 2's control panel enables you to change the amount of memory you end up with and shows how much memory each active program has allocated to it, in a manner similar to the About This Macintosh window, but with far more information. RAM Doubler 2's interface can also break out the different things that chew up system memory (disk cache, MacsBug, invisible background applications, and the Finder, for instance). What's more, it tells you how much memory is in use and (more important) how much memory RAM Doubler 2 has reclaimed.
If you use a Power Mac and have ever opened an application's Get Info window, you know that thanks to a technique called "file mapping," Power Mac-native applications require less RAM (an average of almost 2 MB less, according to Apple) if you use either Apple's Virtual Memory (VM) or RAM Doubler. Applications also load faster if you use VM or RAM Doubler. You can read more about why in Apple's Tech Info Library.
So, it's clear Power Macs should generally have VM or RAM Doubler on, even if they have plenty of real RAM. But here's the kicker: when you turn on VM in the Memory control panel, the minimum setting is for 1 MB larger than the amount of real RAM you have. VM creates an invisible VM Storage file on your hard disk that is the same size as the total amount of memory available after turning on VM. Assume that you have 80 MB of real RAM. Turn on VM and set it to the minimum of 81 MB. Poof, there's 81 MB of disk space gone.
If you set RAM Doubler 2 so that it doesn't provide any more memory at all, it offers the advantages of VM or the previous version of RAM Doubler, but without the speed problems that normally accompany any scheme for faking more memory. This works because RAM Doubler 2 relies on disk swapping only as its final strategy to provide more memory (first it reclaims unused memory in application partitions, then compresses memory it can't reclaim). On my 660AV with 20 MB of real RAM, set to 60 MB, RAM Doubler 2's invisible VM Storage file is currently 390K. I can live with that.
Reasons Against -- Although I'm a definite proponent of RAM Doubler, there are a number of real reasons not to use RAM Doubler 2.
The main one is that RAM is cheap right now (although prices are rising again). There's no question that real RAM is better than RAM Doubler.
Speed: Although RAM Doubler 2 is faster than its predecessor, as you use more of the memory it has conjured up, you will start to see speed hits. I can't offer any testing specifics, other than to say that I haven't noticed speed problems caused by RAM Doubler 2 under normal usage. If you need the utmost in speed, avoid both RAM Doubler and VM.
Lots of RAM and disk space: My argument above for why RAM Doubler 2 is more attractive than VM for Power Mac users with lots of RAM only applies if you are short on disk space too. If you have lots of both, VM is free and works fine. Moreover, the performance of Apple's VM has improved considerably in System 7.5.5 (see TidBITS-346).
Single application users: RAM Doubler has never worked well for providing a single application more memory than the amount of real RAM available. Adobe Photoshop is among the worst in this regard, since it has its own internal memory-mapping scheme. RAM Doubler works best for running multiple applications simultaneously.
Programmers: Although programmers should test their programs with RAM Doubler, the word from my programmer friends is that you can't much use RAM Doubler on a programming machine because of incompatibilities with debuggers and other development tools.
- Anyone without $50: RAM Doubler 2 isn't free, and for the cost of RAM Doubler 2, you can buy about 8 MB of real RAM. If you're a previous owner of RAM Doubler, there's a $25 rebate coupon in the box for you to mail in.
Reasons For -- Despite these important reasons to avoid RAM Doubler 2, I think there are plenty of reasons to investigate it more seriously.
Minimal money: RAM Doubler 2 may cost about the same as 8 MB, but if you have say, 20 MB now, RAM Doubler 2 can double or triple that amount, which is a lot more than 8 MB.
Older Macs: Frankly, I don't think it's worth buying RAM for older Macs that use SIMMs, like my 660AV. SIMMs won't be useful in any new Mac (which use DIMMs), so if you plan to upgrade soon, RAM Doubler 2 is a better investment. It will work on your new Mac (though you may have to download a minor update), but SIMMs definitely won't.
Power Macs without much disk space: Whether or not you have much RAM, a Power Mac runs better with either VM or RAM Doubler on. If you lack disk space (and yes, I know hard disks are cheap too - but lots of people have little money to devote to computer purchases), RAM Doubler 2 uses fewer total resources than VM and provides more RAM, since Apple recommends you only set VM for 50 percent more memory than you have real RAM.
- PowerBooks: Because RAM Doubler doesn't go to disk immediately to swap memory, RAM Doubler can be less draining for PowerBooks than VM, which can keep the hard disk spinning. In addition, most PowerBooks (and some desktop Macs) have only a single slot for adding more memory, and using RAM Doubler can be a lot easier than ordering and installing new RAM.
In the End -- Some utilities are easy to recommend because they offer features unavailable elsewhere. That's not true of RAM Doubler, since Apple's VM is free. However, the fact that RAM Doubler sold over a million copies and RAM Doubler 2 sold 50,000 copies in its first month indicates its overall utility to the Mac community. I couldn't use my aging 660AV without RAM Doubler (I actually launch more applications at startup than I have real RAM for), and RAM Doubler 2 has been a pleasant upgrade, in part for the RAM-tripling and new interface, and in part for the file mapping capability for my PowerBook 5300, which has enough real RAM at 24 MB and prefers to keeps it hard disk spun down.
A Deal -- We've worked out a special deal for TidBITS readers with Cyberian Outpost. If you use the specific URL below, you can order RAM Doubler 2 online and receive a $4 discount (think of it as free shipping).