On Wed, 15 May 2019 18:12:19 -0500, Tom Marchant <m42tom-ibmm...@yahoo.com> wrote: >The s/360 POO (available on bitsavers), says, >"A control unit may be housed separately or it may be physically >and logically integral with the I/O device."
The classic example of early CU integration was the 2701 communications controller and the integrated CTC adapters. Disk, tape, and unit record devices of the same era had discrete controllers. Unit record CU (2821) was interesting in that it talked to devices that did different things: 1403/1404 printer and 2540 card reader-punch. Clever of them. But the up-and-coming display devices (3275) and printers (3211) were a visible hybrid with an "attached" CU. 3211 still named it separately (3811). Kinda weird. 3430 tape had integrated CU in the A units, and after that I think integrated CU was de rigueur for all device types, with 3990 being the last one on the floor. (BTW, once someone explains CU integration, the whole A/B model numbering thing makes more sense.) I had always assumed that latency was driving engineers to shorten the distance between CU and device. Alan Altmark IBM ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
