You see their ads in all the computer magazines. And, if you're a true computer geek with older hardware, you drool with anticipation over what they claim to do. So, when I was given the chance to test several products from Evergreen Technologies, how could I say no?

For those who aren't familiar with the name, Evergreen makes CPU (central processing unit) upgrades for computers that have lived past their prime.The Evergreen Performa 500 ($129 after a $50 rebate) is made to boost the processing power of older Pentium II computers to the speed of a low-end Pentium III. I tested it with a Pentium II 300-megahertz machine and it was soon operating at 500 megahertz.

Another replacement CPU, an AcceleraPCI ($429 after a $70 rebate) upgrade with 256 megabytes of memory, transformed my old Pentium 200-megahertz machine into a faster 466-megahertz computer.

There are some distinct differences between the two upgrades. The Performa is actually a replacement for your old CPU. You just swap one for the other. The Accelera is a chip on a PCI board that allows you to keep your old CPU in the machine. The Accelera board is inserted into an empty PCI slot in your computer. This means your old Pentium will boot up using the old CPU before the new one kicks in.

Both needed some additional tweaking and some handholding from Evergreen's support staff before they were ready for prime time. But I'm told that's not always the case and they work right out of the box for most folks. That's probably true, because a lot of the problems I had were caused by some modifications I had made previously to both machines.

Even if that's not the case, it was worth the effort. Both computers are now humming along as though they were designed to be 466- and 500-megahertz speed demons.

I also had a chance to play with Evergreen's fire-wire products, which boost the speed of your computer even more significantly. These included a FireLine CD-RW drive ($299 after a $100 rebate), a FireLine 20-gigabyte hard drive ($249.99 after a $250 rebate), a FireLine PCI card ($89 after a $30 rebate) and a FireLine CardBus/PCMCIA card ($84 after a $35 rebate).

FireWire interfaces can handle data 40 times faster than universal serial bus (USB) and even fast than serial or parallel interfaces. All of the devices are true ''plug-and-play'' and can be ''daisy chained,'' whereby one device can be hooked into another.

Almost everything lived up to the hype. The hard drive handles data at a blazing two milliseconds, compared with nine-millisecond ratings of the newer IDE hard drives; I was able to install both fire-wire interface cards with a minimum of effort; but the fire-wire CD-RW drive still ran as a clunky old CD-RW drive.

I had expected it to leave my older CD writers in the dust, but it didn't. In fact, it was slower than the HP9110i I had been using. Upon further investigation, I discovered that it was actually a Ricoh 6x drive, which is designed to record data at 900 kilobytes a second. My Hewlett-Packard, which is an 8X drive, handles data at 1,200 kilobytes a second. This means that it takes the FireLine drive 9.5 minutes to record 450 megabytes of data, compared with the seven minutes it took my old drive to do the same thing.

And now, with 12x CD writers hitting the market, which should handle the same data in three or four minutes, I was a bit disappointed.

Overall, I'd buy anything that has the Evergreen name on it, except the CD writer. For that, I's wait until the technology of the hardware catches up to the capabilities of the fire-wire interface, as they have with Evergreen's hard drive.