Editing IBM System/370 (section)

=====IBM 4300=====
{{main article|IBM 4300}}

The first pair of '''IBM 4300''' processors were Mid/Low end systems announced Jan 30, 1979<ref>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4331.html|title=4331 Processor|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20231209132724/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4331.html|archive-date=2023-12-09|url-status=dead}}</ref><ref>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4341.html|title=4341 Processor|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230719223403/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4341.html|archive-date=2023-07-19|url-status=dead}}</ref> as "compact (and).. compatible with System/370."

The 4331 was subsequently withdrawn on November 18, 1981, and the 4341 on February 11, 1986.

Other models were the 4321,<ref>{{Cite web|url=https://www.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology5.html|title=IBM Archives: DPD chronology - page 5| website=[[IBM]] |date=23 January 2003 |archive-url=https://web.archive.org/web/20201021214611/https://www.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology5.html |archive-date=2020-10-21}}</ref> 4361<ref name="IBM.4361">{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4361.html|title=4361 Processor|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230914064000/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4361.html|archive-date=2023-09-14|url-status=dead}}</ref> and 4381.<ref name="IBM.4381">{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4381.html|title=4381 Processor|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230719145726/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4381.html|archive-date=2023-07-19|url-status=dead}}</ref>

The 4361 has "Programmable Power-Off -- enables the user to turn off the processor under program control";<ref name="IBM.4361"/> "Unit power off" is (also) part of the 4381 feature list.<ref name="IBM.4381"/>

IBM offered many Model Groups and models of the 4300 family,{{efn|One announcement alone featured mention of "Twelve models of the 4381" for just 3 "Model Groups" and also listed 6 other Model Groups}} ranging from the entry level 4331 to the 4381, described as "one of the most powerful and versatile intermediate system processors ever produced by IBM."{{efn|The same IBM web page notes the following date announced/withdrawn dates: Model Groups '''1 & 2''' (Sep 15, 1983 - Feb 11, 1986), Model Group '''3''' (Oct 25, 1984 - Feb 11, 1986), Model Groups '''11, 12, 13 & 14''' (announced Feb 11, 1986), Model Groups '''21, 22, 23 & 24''' (May 19, 1987 - Aug 19, 1992).}}

The 4381 Model Group 3 was dual-CPU.