And then there were double-ended strings of disks. 3350s? Just before my time, really.
Martin Packer zChampion, Systems Investigator & Performance Troubleshooter, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker Podcast Series (With Marna Walle): https://developer.ibm.com/tv/mpt/ or https://itunes.apple.com/gb/podcast/mainframe-performance-topics/id1127943573?mt=2 Youtube channel: https://www.youtube.com/channel/UCu_65HaYgksbF6Q8SQ4oOvA From: Seymour J Metz <sme...@gmu.edu> To: IBM-MAIN@LISTSERV.UA.EDU Date: 17/05/2019 15:18 Subject: Re: Ancient DASD connectivity Sent by: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> T A unit attached to a CU; it was the CU that attached directly to the channel. There is some overloaded nomenclature here; the control function of an A unit is entirely different from a control unit. -- Shmuel (Seymour J.) Metz https://urldefense.proofpoint.com/v2/url?u=http-3A__mason.gmu.edu_-7Esmetz3&d=DwIFAw&c=jf_iaSHvJObTbx-siA1ZOg&r=BsPGKdq7-Vl8MW2-WOWZjlZ0NwmcFSpQCLphNznBSDQ&m=sbtcjKhJzgcjkqtihVmO6CFwHrRj5q-KUW7yT03NU7Q&s=UjmNKh0zJMgKPveYfD_9y2AfqLn86GvSJJsO6tUpx0Y&e= ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of Alan Altmark <alan_altm...@us.ibm.com> Sent: Friday, May 17, 2019 10:02 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Ancient DASD connectivity On Thu, 16 May 2019 15:26:45 +0000, Seymour J Metz <sme...@gmu.edu> wrote: >Well, for some devices the CU and device were in the same box, e.g., 2501. Yes. A-units (Axx models) often include(d) at least one, possibly two or even four, I/O devices, with B units (Bxx models) providing expansion. Last CU standing in the A/B world was, I think, the IBM 3590, but it all went out the window when the 3592s made their debut. While it was interesting for IBM to wear it's engineering designs on its visible sleeve, it was confusing. Model numbers today are more expressions of marketing than of the underlying technology. Fun times. Alan Altmark IBM ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
