Benchmark tests on our test Windows XP laptop found the cutoff point to be at about 1.5GB of RAM. After that, adding more RAM resulted in smaller and smaller performance boosts.

In fact, the last gigabyte of RAM added, which brought the total to 4GB, increased overall performance by less than 1 per cent and lowered battery life by 15 minutes. Most people will not find this to be an acceptable trade-off.

These tests were run on a Windows XP machine. Given the higher resource demands of Windows Vista, it is reasonable to assume that the peak benefit in terms of adding RAM to a Vista system would occur at about 2GB.

Solid-state or hard disk storage?

Deploying the right amount of RAM can lead to both improved performance and decreased battery life. However, replacing a magnetic hard drive with a flash-memory-based SSD drive is a "two-fer" gain that both increases performance and extends battery life. There are, however, other trade-offs to be aware of.

My test laptop had a 60GB hard drive that spins at 5,400 rpm. Note that this speed, while not as fast as most hard drives found on desktop computers, is by far the most common type of disk found on laptops, largely because faster hard drives demand more battery power.

In my tests, switching from a traditional 60GB hard drive to a 32GB Samsung flash drive boosted storage performance, or the notebook's ability to find and retrieve data, by 50 per cent while using 38 per cent less power.

All told, the system delivered an extra 20 or 25 minutes of battery life when using the flash drive than it did with a traditional mechanical hard drive. Overall system performance increased by 10 per cent.

At a more micro level, another test, the HD Tach benchmark, found that the SSD drive read data 45 per cent faster than the hard drive. In addition, the flash drive's random access time, which measures the lag the drive incurs to find the needed data, was just 0.3 milliseconds, a fraction of the hard drive's 17.9-millisecond access time.

Those performance results are not surprising, given that hard disk drives are largely mechanical, with spinning disks and read-write heads that locate information. In contrast, solid-state flash memory chips have no moving parts and can find and transfer data much more quickly than a hard drive's spinning disk. Another advantage is that SSD drives are nearly indestructible and are perfectly quiet.

In fact, the only time the hard drive excelled was in burst data transfers, in which, for brief periods, large amounts of data are transferred at once. The magnetic drive was more than twice as fast as the SSD at bursting data. This is a result of the hard drive using the newer SATA interface, which is capable of 150Mbit/sec. throughput and bursts of 600Mbit/sec. In contrast, the SSD uses the older IDE interface, which runs at a maximum of 133Mbit/sec.

A more serious trade-off of SSDs, however, is that they are currently very expensive. Our 32GB test unit, for instance, cost US$520, compared with about US$75 for a traditional hard drive. And these new drives don't have nearly as much available storage capacity as traditional hard drives -- for most users, 32GB is just not enough space, especially at the price. That's changing -- Samsung reportedly will introduce a 256GB SSD this fall -- but prices likely will remain very high.