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37 votes
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Were any IBM mainframes ever run multiuser?

Yes. There were CP/CMS and VM/370 - true multiuser operating systems running on the mainframe with individual users logged in. AFAIK it was mainly used for software developers (to develop IBM ...
davidbak's user avatar
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21 votes

Were any IBM mainframes ever run multiuser?

IBM mainframes are still around (IBM Z). Linux has been available for IBM Z hardware and its predecessor, System/390, for 20 years, and z/OS is itself a certified UNIX through the z/OS UNIX System ...
Michael Graf's user avatar
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20 votes

Were any IBM mainframes ever run multiuser?

Another one to mention is MTS which was first released in 1967, last release in 1988. It was in use at Rensselaer Polytechnic Institute from 1976 to 1999, of which I took part during the early 80s. In ...
Ross Presser's user avatar
20 votes
Accepted

What is the purpose of the yellow wired panels on the IBM 360 Model 20?

What is the purpose of the yellow wired panels It's the backplane, simply the wiring of the machine. on the IBM 360 Model 20? Not just there, but next to every mainframe was made that way. ...
Raffzahn's user avatar
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15 votes
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What's the deal with System/360's "USASCII" mode?

I found the explanation in chapters 23 and 20 of Mackenzie, Charles E, Coded Character Sets, History and Development (Addison-Wesley, 1980), which was linked in a footnote to Wikipedia's ASCII article....
hmakholm left over Monica's user avatar
11 votes
Accepted

Was the IBM S/360 Responsible for Popularizating the 'A'-to-'F' Notation in Hexadecimal Numbers?

TL;DR: How true is this claim? It's true. While others used it before, it was the success of the /360 making it the default way around the industry. The long read: [Preface: I love the shown ...
Raffzahn's user avatar
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11 votes

Data length module of 3.2^n confusion in IBM system/360 architecture

The notation 3.2n looks to me like it means 3 x 2n rather than (3 point 2)n. So the question is whether data lengths should be based on a 6-bit unit or some 'binary' size, in practice 8 bits. The ...
dave's user avatar
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11 votes
Accepted

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers These issues are unrelated. Registers are about addressing, so they need to hold an address word. Byte addressable ...
Raffzahn's user avatar
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10 votes

Were any IBM mainframes ever run multiuser?

But were any of them used like the college-lab VAX, to provide a bunch of people with interactive shell accounts that could run arbitrary code? Absolutely 100%! TL;DR University of Maryland - ...
manassehkatz-Moving 2 Codidact's user avatar
10 votes

Mainframe Hater's Handbook?

"The Unix-Haters Handbook" is a product of a particular time and place that made an entire book possible, the rise of RISC workstations and the Internet. People had been grumbling about ...
Hugh Fisher's user avatar
10 votes

Were any IBM mainframes ever run multiuser?

Certainly. A place where I worked in the early 1980s had an IBM 4341 system running some species of MVS, with the TSO ('time sharing option') that supported interactive program development. I'm ...
dave's user avatar
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8 votes

What is the purpose of the yellow wired panels on the IBM 360 Model 20?

Couldn't find much on the purpose but physically those appear to be terminals that are used for wire-wrapping. You see this application used in all manner of early electronic equipment and its used ...
Hogstrom's user avatar
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8 votes
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Data length module of 3.2^n confusion in IBM system/360 architecture

Note that 3.2 is the square root of 10 rounded up to the closest value with one digit after the decimal. Thus, every other data length module will be slightly greater than a power of 10. Apparently ...
Leo B.'s user avatar
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8 votes

Were any IBM mainframes ever run multiuser?

Thus it was necessary or at least highly beneficial for the operating system to use memory protection to screen the users from each other ... That "memory protection" scheme is typically ...
sawdust's user avatar
  • 180
6 votes

Were any IBM mainframes ever run multiuser?

Circa 1970, MIT's EE department operated an APL\360 virtual machine under CP/67 on an IBM 360/67. APL\360 was a multiuser dialup system for 360 mainframes, specialized for APL, but virtualizing it ...
John Doty's user avatar
  • 2,995
6 votes

Were any IBM mainframes ever run multiuser?

The University of Cambridge (UK) Computing Service acquired a 370 around 1972 at the time I was starting my Ph.D, and operated it as a time-sharing service. Using experience from the Titan operating ...
Michael Kay's user avatar
6 votes

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers

There is no downside I can see to storing an 8-bit quantity in a 32-bit register if you already have the 32-bit register. Load/store take the same amount of time. Memory transfers are at least word-...
dave's user avatar
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5 votes

Did any 360-compatible machine implement registers in core?

Did any 360-compatible machine ever actually implement its registers with magnetic cores? Yes, of course, in fact, it was standard for low end machines. Beside IBM, as Ross Ridge details, many early ...
Raffzahn's user avatar
  • 228k
5 votes

Were any IBM mainframes ever run multiuser?

Wikipedia has this: https://en.wikipedia.org/wiki/Time-sharing_system_evolution IBM features heavily.
Kartman's user avatar
  • 285
5 votes

Were any IBM mainframes ever run multiuser?

To add to all this, System/370 with virtual memory was one of the first platforms (perhaps the third) that UNIX was ported to. You can read a paper about that porting done here. IBM would follow it ...
RETRAC's user avatar
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5 votes

Were any IBM mainframes ever run multiuser?

In the 70's I used Orvyl and Wylbur extensively on Stanford's 360/67, which Wikipedia says were originally developed in 1967-68. There were golfball terminals all over campus. Keypunched batch jobs ...
joe snyder's user avatar
4 votes

Were any IBM mainframes ever run multiuser?

Yes To add to the UM students above we had a 7090 in the mid 60s that any student could run their own program on by submitting a punch card deck to the computer center. You picked up the print out and ...
IBM SE's user avatar
  • 41
4 votes

Were any IBM mainframes ever run multiuser?

Lots of good information here but as an ex-MVS sysprog I would like to approach it from a different direction. The MVS/370 operating system (Multiple Virtual Storage on 370 architecture) was an OS ...
Paul Meekin's user avatar
3 votes

Were any IBM mainframes ever run multiuser?

Yes, I had a timeshare account on my university's IBM System/360 in the early 1970s where I wrote and debugged programs in APL. The computer center had several dumb terminals that students could use ...
MTA's user avatar
  • 149
2 votes

Were any IBM mainframes ever run multiuser?

CTSS at MIT was one of the first timesharing systems ever built. It ran on a modified IBM 7094 mainframe. This is from the 1963-1966 time frame. Memory protection was extremely primitive. There were ...
Walter Mitty's user avatar
  • 6,158
2 votes

Were any IBM mainframes ever run multiuser?

Most large System/360 and System/370 installations were multiuser. I never saw a University whose S/360 or S/370 was not multiuser, and I never worked on a machine larger than a 360/50I that was not ...
shmuel's user avatar
  • 121
2 votes

Were any IBM mainframes ever run multiuser?

Many answers mention interactive timesharing systems, but, even in a purely batch environment, there would typically be multiple jobs (i.e. processes) loaded into main memory at once and the CPU would ...
Theodore Norvell's user avatar
2 votes

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers

Did they have any performance improvements for such decision? If so, why do we have 8-bits registers today? Most 32-bit non-x86 CPU types today still only have 32-bit registers but they can access ...
Martin Rosenau's user avatar

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