BITBLT arg checking ?

[TAFT at MIT-AI (Jonathan D. Taft)]

   While BITBLTing I happened to quote the TV:ALU-FUNCTION argument [ 'TV:ALU-SETA ].
Instead of dying in any reasonable fashion some gross unknown quantity got mashed into
some microinstruction and the machine went off the deep end. Not only was there no
argument check (perhaps OK for speed ?) but apparently the ALU spec was not even
masked to fit into its field. The reason this seems important was because of the degree
of machine death induced. It was not possible to warm OR cold boot from the keyboard,
I had to frob the wire. (It was not a question of number of trys or anything - I can
repeat it.)