The IBM 4300 series[1][2][3][4][5] are mid-range systems compatible with System/370[2] that were sold from 1979 through 1992. They featured modest electrical and cooling requirements, and thus did not require a data center environment. They had a disruptive effect on the market, allowing customers to provide internal IBM computing services at a cost point lower than commercial time-sharing services. All 4300 processors used a 3278-2A, 3279-C or 3205 display console rather than a 3210 or 3215 keyboard/printer console.
The 4381-13 through 4381-24 (announced in 1987) were entry-level machines for the 370-XA architecture. They were positioned between the IBM 9370 and IBM 3090 in performance at the time of announcement.
The 4381-3, 4381-14, 4381-24 and 4381-92 are dual-CPU models. Other models included 1, 2, 11, 12, 13, 21, 22, 23, 90 and 91.
The IBM 4331 (and the 4341) were announced on 30 January 1979.[2] It came with an integrated adapter that permitted attaching up to 16 of two newly introduced direct-access storage devices (DASD):
The IBM 3310, described as having "a storage capacity of 64.5 million characters", was to be used with "Storage disks .. sealed to reduce the possibility of damage, loss, misuse or contamination".
The IBM 3370 with up to 571 million characters could also be used with an IBM 4341.
The IBM 4341 (and the 4331) were announced on 30 January 1979.[3] Like the 4331, it came with an integrated adapter that permitted attaching up to 16 of the newly introduced IBM 3370 DASD. The 4341 did not support the much lower capacity IBM 3310. The 4341 Introduced the Extended Control Program Support:VM (ECPS:VM), Extended Control Program Support:VS1 (ECPS:VS1) and Extended Control Program Support:Virtual Storage Extended[6][7] (ECPS:VSE) features. The 4341-2 introduced the Extended Control Program Support:MVS[8][9] (ECPS:MVS) option, a subset of System/370 extended facility.
On 20 October 1982, IBM announced a new entry-level 4341 model, Model Group 9 and a new top-of-the-line 4341, Model Group 12. Model Group 12 included the Dual Address Space (DAS) facility.
Among the new/optional features for the 4361 were:
Auto-Start—automatically turns on the processor by telephone via the Remote Operator Control Facility or at a predetermined time and day of the week. The processor powers on and proceeds with initial microcode load, sets the clock and loads the system.
^Described by IBM as "High-Accuracy Arithmetic Facility: Allows computational procedures with algorithmic verification of results." and adds "New floating-point instructions are implemented for computation of basic arithmetic operations and the scalar product with maximum accuracy."
^"Section 01: Highlights"(PDF). A Guide to the IBM 4341 Processor(PDF). Systems (First ed.). IBM. April 1979. p. 2. GC20-1877-0. Retrieved 2023-03-30. ECPS:VSE mode provides an alternative method for translating addresses in instructions during instruction execution and, in addition, provides for translating addresses in channel command words during I/O operations. The address translation technique used in ECPS:VSE mode permits only one virtual storage of up to 16 million bytes to be supported.
^Lortz, Bruno (1971). Eine Langzahlarithmetik mit optimaler einseitiger Rundung [A large-number arithmetic with optimal one-side rounding] (Ph.D. thesis) (in German). Universität Karlsruhe.
