The downside, of course, is that as the
hobbyist-end-user, you are
somewhat out in the cold if you don't own a GAL programmer. They can
easily run to hundreds of dollars for basic ones, and, unlike an old
4K EPROM, they are not trivial to make programmers for from scratch.
There are no excuses ..
http://www.geocities.com/mwinterhoff/galblast.htm
Lee.