Phil, The terms originated in the IBM 360 “principles of operation” book which I have here for the model 67. To wit: “instructions operate on units called halfword (2 bytes), fullword(4 bytes), doubleword (8 bytes), quad word (16 bytes). FWIW The IBM ‘storage block’ was 2048 bytes which was different from what DEC and much of the rest of the world used. Also the 67 used a 2 block (4096) byte page size.
Also, my friend Russ Robelen (360/50 hw lead) says we can credit the 8 bit byte to Fred Brooks. According to Russ, Amdahl wanted a 6 bit byte (like Cray was using at CDC) but Brooks kept throwing out of his office and told him not to come back until ‘everything was a power of 2.’ Supposedly Amdahl thought it was a waste of HW but Brooks told him unless it was a power of 2 he couldn’t program it. Amdahl did get a 24 bit address size but Brooks made him store it in a ‘full word’ which Gordon Bell later has been said to have been what saved the 360 architecture. Clem Sent from my PDP-7 Running UNIX V0 expect things to be almost but not quite. > On Apr 5, 2019, at 6:33 PM, Phil Budne <p...@ultimate.com> wrote: > > Johnny Billquist <b...@softjar.se> wrote: >> In DEC terminology those are words. >> It goes: byte, word, longword, quadword, octaword. (8, 16, 32, 64, 128 >> bits.) >> Halfword is something that I first saw on Motorola 68K, but maybe it's >> been used elsewhere as well. But it feels wrong to use that terminology >> on DEC systems. > > Well, in the DEC VAX world! > > I came from the DEC world of 36 bit words, and 18 bit halfwords. > > I was a member of of the SAFE project, a 64-bit VAX datatype > compatible RISC machine led by Alan Kotok (the KA10 designer). > Instructions were named by how many bits they operated on. When > Cutler absconded with the project and renamed it PRISM, they replaced > 8/16/32/64 with B/W/L/Q. > > Morons. > > Phil > _______________________________________________ > Simh mailing list > Simh@trailing-edge.com > http://mailman.trailing-edge.com/mailman/listinfo/simh _______________________________________________ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
