For me the dead giveaway was not thr labelling of the rollers but rather the 8 word associative memory. It did not make sense that IM designed that just to speed up block relocation, so it was clear that paging was on the horizon.
I've seen two different versions of the history posted here. One version claimed that IBM intended on having paging from the beginning, but delayed it due to engineering problems. The other version is that IBM decided after the fact to add paging. I suspect that this is in the realm of if I knew they'd have to shoot me. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 עַם יִשְׂרָאֵל חַי נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר ________________________________________ From: IBM Mainframe Discussion List <[email protected]> on behalf of Gabe Goldberg <[email protected]> Sent: Sunday, June 2, 2024 4:42 PM To: [email protected] Subject: Re: Upgrade by cutting a wire? Yes-and-no, sort-of: On September 23, 1970, IBM announced the Model 145, a third model of the System/370, which was the first model to feature semiconductor main memory made from monolithic integrated circuits and was scheduled for delivery in the late summer of 1971. All subsequent S/370 models used such memory. The IBM System/370 Model 138 which was announced Jun 30, 1976... The IBM System/370 Model 148 had the same announcement and withdrawal dates as the Model 138 As with the option to field-upgrade a 135, a 370/145 could be field-upgraded "at customer locations" to 148-level performance. The upgraded 135 and 145 systems were "designated the Models 135-3 and 145-3." https://en.wikipedia.org/wiki/IBM_System/370 Announced six years apart (145/148) I suspect the upgrade was more than snipping. And 145 didn't become 148, was 145-3. Mitre installed early 370/145 (whenever VM/370 Release 1 PLC 9 was current), then real 370/148 (I've no idea why 145 wasn't upgraded). Ah: 145 had up to .5MB IBM RAM, 148 had 2MB. Although other vendors added more memory than IBM supported. I did a competitive procurement to add .25MB to 145, cost $30,000. Couple years later, same for 148 to add 1MB -- also $30,000. Maybe you're thinking of this: Initially, the System/370 Model 145 did not support virtual memory. Unlike the earlier Model 155 and 165 systems, for which an upgrade to virtual memory required the purchase of an expensive upgrade to add a DAT box,[5] the Model 145 already included an associative memory[6][7]: CPU 117-CPU 129 used by the microcode for the DOS compatibility feature from its first shipments in June 1971;[6] the same hardware was used by the microcode for DAT.[7]: CPU 139 Although IBM famously chose to exclude virtual storage from the S/370 announcement, that decision was being reconsidered during the completion of the 145 engineering, partly because of virtual memory experience at CSC and elsewhere. The 145 microcode architecture simplified the addition of virtual storage, allowing this capability to be present in early 145s without the extensive hardware modifications needed in other models. However, IBM did not document the 145's virtual storage capability, nor annotate the relevant bits in the control registers and PSW that were displayed on the operator control panel when selected using the roller switches. The Reference and Change bits of the Storage-protection Keys, however, were labeled on the rollers, a dead giveaway to anyone who had worked with the earlier 360/67. Existing S/370-145 customers were happy to learn that they did not have to purchase a hardware upgrade in order to run DOS/VS or OS/VS1 (or OS/VS2 Release 1 – which was possible, but not common because of the limited amount of main storage available on the S/370-145). This resulted in two advantages of the 145 over the 155 and 165: 370/145 customers did not have to wait as long for this lack of virtual memory to be remedied[b] there was no need to buy extra hardware: An upgrade to the 145's microcode through a new microcode floppy disk[8] enabled virtual memory capability. https://en.wikipedia.org/wiki/IBM_System/370_Model_145 Date: Fri, 31 May 2024 08:51:22 -0500 From: "Lionel B. Dyck"<[email protected]> Subject: Re: Upgrade by cutting a wire? I recall hearing the 370/135 and 370/145 could be upgraded to 370/138 or 370/148 with a snip but that was 2ne/3rd hand. Lionel B. Dyck <>< Github:https://github.com/lbdyck System Z Enthusiasts Discord:https://discord.gg/sze -- Gabriel Goldberg, Computers and Publishing, Inc. [email protected] 3401 Silver Maple Place, Falls Church, VA 22042 (703) 204-0433 LinkedIn: http://www.linkedin.com/in/gabegold Twitter: GabeG0 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
