ImageMagick to split up images

[Dave Smith]

>> I've got some largish jpg files that I want to split into smaller jpg
>> files.

> To do that I'd probably use "identify" to get the width and height in
> pixels of the image, and then use "convert -crop" to split the thing up.
> http://www.cit.gu.edu.au/~anthony/graphics/imagick6/crop/index.html

This appears to be what I want, but when I run "convert -crop 200x200
myimage.jpg out.jpg", convert works and works, until it has used up over
400MB of memory, and it's still not done (machine is 3.2GHz with 1Gb RAM).
What I want to accomplish is to chop my 20,000 x 20,000 pixel jpg into a
tileset of 200 x 200 pixel jpg files. I'm not sure  ImageMagick's convert
can handle these sizes. Any recommendations?

--Dave