Sunday, March 27, 2005

The biggest ROM ever built.

Well, it will be, anyway, if I do manage to build it. This ROM is 256 words of 16 bits each: 0.5KB. It will probably also comprise more than a ton of building materials. It uses about 9180 gates and nearly 14000 connections. Of course, you could remove 4096 gates and 8192 connections if you don't mind programming it by moving connections around, instead of just flipping gates. If you rarely reprogram it, that might be a big win; it'd be just like the old electronic computers which were programmed by plugging wires into switchboards.

This diagram is scaled way down from the others, and is the first that I've chosen to post with full-depth drawing turned on [so that you can see inside each of the smaller 16x16 ROM cells].

Incidentally, speaking of scaling: I realized the other day that I've been posting mostly full-scale images. The code that dumps out screen shots was supposed to have been putting out images scaled down to 60% of regular size, but it turned out that it was only scaling down the top-level diagram, and that all of the other images linked from there are full-scale. I may go back and fix that up [now that I've fixed my code], but it's a bit of a pain to get it all set up, so that may take a while. While the tool dumps out images and image maps for me, it's still a bit of manual scutwork to get it all into blogger + photobucket.

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