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Old 2004-08-23, 08:53   #3
xilman's Avatar
May 2003
Down not across

253058 Posts

Originally Posted by Doorbasher
Hey evryone.

I have a few spare computers at home, and I like the idea of them doing something useful. Problem is, they might be too elderly to make a contribution, so I decided to check here first.

The first rig is a Pentium 60. I know that an 80586-class machine is powerful enough to do some factoring work, but there's a catch. I tested it, and it has the infamous bug in the floating-point divide instruction. (The FDIV bug). Now I don't want to turn in incorrect results. Is there a way to force the program to use an integer-based routine, or otherwise avoid the floating-point divide?

Next up is an 80486DX, running at 20 MHz. This one might have a problem with memory, it only has 5 MB at it's disposal. Enough power?

The final one, a 25 MHz 80486SX. No math coproscessor. This one runs on 12 MB I think, but I'm not sure how lack of an FPU will affect things.

I suppose my 8 MHz 80286 is beyond hope.

Anyhow, is it woth keeping these old rigs in service?
I keep a bunch of old machines in service though, not at the moment, anything quite as slow as a 486. Until about a year ago I had some DECStations running which were about as powerful as a 486DX2-66.

Anyway: all those machines can do something useful but you have to decide first whether you want to keep them powered up. Where I live has a miserable climate and so running fan heaters is fairly good idea most of the year. Getting computation from my heaters is a bonus.

What you may find difficult is using George's code to work on old systems because, as you point out, some of them don't have either enough memory and/or a working fpu. If you are prepared to download other software, UBASIC for instance, you can try factoring relatively small Mersenne numbers with ECM.

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