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Space Doubler is an automated compression/decompression system for your Nokia S60 Mobile that effectively unpacks your applications just before you use them and packs them after you've finished. The idea is not new in the portable world, but the N-Gage has one specific quirk that makes this product more valuable than it otherwise would be.

The idea really is simple. Take an installed application, compress it and add a header that calls the decompression library when the program is run. Decompress the program into available RAM, delete the packed version, then run the app. When the user closes the application, pack it back up. The thought is that with most of the applications in RAM compressed, and few if any needing to be used simultaneously, you've got more room to make available applications, well, available.

The obvious trade-off is time. Every time you want to run an application you have to decompress it first. Because of the limited space, you can't keep both the packed and unpacked version in RAM, so you also have to wait for the application to be packed up after you've finished. Thankfully, Space Doubler has four compression modes specifically to allow you to decide where your preferred time vs space trade-off point is.

What's less obvious is that the space savings simply aren't as great as the program makes out. With 2,094k of applications, 1,580k of "other data" (mostly Java apps, which can't be compressed in the same way and don't compress very well anyway), Space Doubler is reporting that it's saving me 825k. Thing is, the program itself weighs in at 94k. More importantly, unless I miss my guess, you need enough available space for your largest application to unpack into. For me, that's currently 570k. So, really, I've only gained 161k out of 3,764k. That's a ratio of 1.02:1, not 2:1.

Now, I have been tough on this little app. 570k is a large program for a 4Mbyte device. Many people are more likely to have a collection of 100k to 250k tools. And it can be made to automatically pack and unpack data associated with an application at the time that the application is run, I just don't have a lot of data yet.

So, really, you should just invest in a cheap MMC card (if your Series 60 has a slot for one) and really gain the space you need. This brings us to the N-Gage quirk I mentioned as the beginning. If you want to play a commercial N-Gage title that's distributed on MMC, you have to remove your MMC data card and replace it with the game card. This makes fitting into RAM the stuff you want all the time that much more important. Since you can't buy more internal RAM for the N-Gage, I bought Space Doubler. Once I've chosen my-haves, I'm confident that Space Doubler will score me at least an extra MB to play with.

Recommended for:

• People with a Series 60 phone that doesn't have an MMC slot.
• People specifically intending to play the major games on the N-Gage.
• People who think automated application compression on a phone is just too funky to pass up.