rbbb@rice.ARPA (04/09/84)
From: David Chase <rbbb@rice.ARPA> Can anyone out there explain the "comet sucks" at line 123 of doprnt.s? This is for 4.1BSD. I already know that "comet" refers to the 11/750, and I already know about many alleged and actual microcode bugs on that machine; what bug are they talking about right here?? loop: movzwl $65535,r0 # pseudo length movl r11,r1 # fmt addr # comet sucks. movq *fdesc,r4 subl3 r1,r5,r2 drc
johnl@haddock.UUCP (04/21/84)
#R:sri-arpa:-1210000:haddock:16800011:000:658 haddock!johnl Apr 20 15:08:00 1984 The "comet sucks" comment in the 4BSD printf routine refers to the annoying fact that the Vax 750 "movtuc" instruction, which used to be in printf's inner loop, doesn't work right and sprays crud all over memory at inconvenient times. Actually, movtuc turned out to have two bugs in it. Bill Joy found one, added the comment, and fiddled the code a little but didn't take out the movtuc. I found the other and completely removed the movtuc. The ramifications were pretty strange. While fighting that bug, I tried recompiling the C compiler, and it took three iterations until it converged to the same object code twice in a row. John Levine, ima!johnl