Tuesday, March 01, 2005

I remember when 16k was a lot of memory

If an old computer is running slowly, the easiest way to do something about it is almost always to install more RAM. New software amd new operating systems use more memory than old ones. If there is not enough RAM, then a lot of the data has to be stored on the hard disk instead of in RAM, data has to be constantly swapped back and forwards, and everything goes slower. (As a bonus, all the hard disk activity means that there is more danger of the disk failing, and if you are using a laptop this all runs down your battery faster). Many a computer has been thrown away as slow and out of date and replaced by a new one when a RAM upgrade would speed it up considerably and make it useable for some time longer. (Non technical people often fail to grasp the distinction between storage and memory, so this point is sometimes difficult to explain).

In any event, Windows XP is known as a bit of a memory hog, and for this reason I won't build a computer with less than 512Mb of RAM, because performance with less than this is generally poor. (XP is not alone on this score - you need 512Mb for decent performance on Mac OS X, too). If someone is buying a computer from an OEM, I strongly recommend either that they buy it with 512Mb or they get me to upgrade the RAM immediately after they buy it. (The second option is usually more cost effective, as OEMs seriously overcharge for memory upgrades). I make it very clear that I think that sticking with 256Mb is asking for trouble. (The situation is even worse if the computer has integrated graphics and the main memory is being used to drive the display as well as run programs, which is often the case on cheap computers).

I have generally argued that 512Mb is enough for good performance, however. If someone who is not financially constrained wants a computer, then 1Gb is worth buying, but to some extent this is insurance against future requirements. When I built myself a new desktop computer a few months back, I put 1Gb in, but to some extent I considered this overkill.

However, recently I found myself doing one of those memory upgrades for a friend with a new laptop. The laptop had come with a woefully inadequate 256Mb and I offered to upgrade it to 512Mb. For this I needed a 256Mb SO-DIMM. As it happened, my own laptop had 512Mb in it, in the form of two 256Mb SODIMMs of the correct type. Rather than buying a 256Mb SO-DIMM, I instead bough a 512Mb SO-DIMM for myself, swapped this with one of the 256Mb SO-DIMMs in my laptop, and then installed that 256Mb SO-DIMM in my friend's computer. This brought the memory in my laptop up to 768Mb.

And what did I find out? I wasn't expecting that much improvement, particularly given that the laptop has separate graphics RAM and main memory is not being shared by the graphics system. But I was badly wrong. As it happened the performance of my machine improved considerably. It is running substantially faster and there is less swapping to disk. I don't know to what extent battery life has improved, but I am sure that it must have. The truth is clearly that more than 512Mb is a good idea even now. I will have to change my recommendations.

But a 768Mb or 1Gb seems like such a gigantic amount of memory. I am not going to claim that 640k should be enough for everyone or anything like that but seriously, what is the computer doing with all that memory?

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