38
votes
Accepted
What was the rationale behind 32-bit computer architectures?
there some particular design theory or constraint that made a 32-bit word size attractive for IBM to migrate to?
It all comes down to the most basic data type, addressing constrains and, less ...
- 213k
37
votes
Accepted
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 ...
- 6,119
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 ...
- 9,820
21
votes
Accepted
Did the IBM 1401 have much better code density than the 360?
TL;DR: No.
/360 code was usually way more compact for the same task than 1401 code. Partly due to shorter instructions (2..6 Bytes vs 1..8 Char
(*1)), partly due to a more capable ISA (use of ...
- 213k
21
votes
Was bootloading from punch cards possible on System/370 machines?
Sorry for the narrative here, but it answers the OP's question directly by personal experience. The text is too long for a comment.
"Was bootloading from punch cards possible on System/370 ...
- 367
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 ...
- 301
20
votes
Accepted
When did IBM start to use ASCII?
TL;DR:
ASCII was never intended for processing, just as an interface standard for data exchange (hence the name American Standard Code for Information Interchange)
IBM never switched, it still uses ...
- 213k
20
votes
Accepted
Was bootloading from punch cards possible on System/370 machines?
TL;DR: Yes, a /360 (*1) can boot from any device connected to a channel.
A /360 can boot from any device able to answer to a basic read command. Whatever is delivered will be executed. There is no '...
- 213k
19
votes
When did IBM start to use ASCII?
IBM started using ASCII before 1970; the 2260 terminal, released in 1964, used the unpublished (but ratified) 1965 version of the ASA X3.4 standard.
IBM mainframes still use EBCDIC, so I don’t think ...
- 118k
12
votes
Why did IBM skip "System/380" as a mainframe family name?
If you have a look at the announcements for the various System/XXX machines you mention, you'll notice a pattern:
System/360, April 1964.
System/370, June 1970.
System/390, September 1990.
Comments ...
- 4,594
12
votes
How did the IBM 360 detect memory errors?
Usage
The /360 Family uses parity all over the system, not just for memory:
One Bit per Byte on
main memory
local storage (*1)
data path
address path
channel data
One Bit per Nibble on
BCD data ...
- 213k
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 ...
- 213k
11
votes
Accepted
The MAC-360 programming language developed in the mid 1960s
An interview with an Apollo Guidance Computer programmer is on-line, and provides some definite information.
It says the guidance software was written in MAC (MIT Algebraic Compiler). MAC-360 would be ...
- 12.4k
11
votes
Accepted
How did the OS/360 link editor achieve overlay structuring at linkage time without annotations in the source code?
How did the OS/360 link editor achieve overlay structuring at linkage time without annotations in the source code?
By getting them as well external in form of control statements?
Mainframe programs ...
- 213k
10
votes
Accepted
Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously
[Please see as well this answer, as it's kind of an extension]
Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously
Not sure what's with /360 reference here, as it's uses byte ...
- 213k
10
votes
How was the APL character set represented on IBM mainframes?
It's important to keep in mind, that there weren't that much symbols using overstrike in basic (IBM) APL. By using an 8 bit codeset they all could be integrated. The most common charset on the ...
- 213k
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 - ...
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 ...
- 33.5k
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 ...
- 180
8
votes
Accepted
Weird example code for CALL/360:BASIC
So... it just errors out and never closes the file? So why is there a line 70?
Left over from the previous program?
Is there unexplained magic here that causes it to continue after 60, or is this as ...
- 213k
8
votes
Accepted
How did the IBM 360 detect memory errors?
The IBM 360 manual Principles of operation says:
The system transmits information between main storage and the CPU in units of eight bits, or a multiple of eight bits at a time. [...] A ninth bit, ...
- 26k
7
votes
Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously
'Byte' was used before it meant '8 bits' and It was used on machines that had word-addressable memory. The point was for the program to be able to read and write data of less than a word size.
The ...
- 33.5k
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-...
- 33.5k
6
votes
Were there "higher level programming" macro packages for the IBM Macro Assembler?
The IBM/360 Macro Assembly language was quite powerful, allowing non-trivial compile-time string manipulation.
Well, reducing it to "string manipulation" might fall short, as there is no ...
- 213k
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 ...
- 1,721
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 ...
- 501
6
votes
What was the rationale behind 32-bit computer architectures?
One small reason is that you can access memory as a bit array without needing to divide (or do a modulo). Just use the bottom N bits for the byte or word or data cache line position or shift, and the ...
- 8,125
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 ...
- 13.5k
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 ...
- 201
5
votes
Were any IBM mainframes ever run multiuser?
Wikipedia has this:
https://en.wikipedia.org/wiki/Time-sharing_system_evolution
IBM features heavily.
- 285
Only top scored, non community-wiki answers of a minimum length are eligible