Lesson plan
31-bit computing
In computer architecture, 31-bit integers, memory addresses, or other data units are those that are 31 bits wide. In 1983, IBM introduced 31-bit addressing in the System/370-XA mainframe architecture as an upgrade to the 24-bit physical and virtual, and transitional 24-bit-virtual/26-bit physical, addressing in System/370. This enhancement allowed address spaces to be 128 times larger, permitting programs to address memory above 16 MB (referred to as "above the line"). Support for COBOL, FORTRAN and later on Linux/390 was included. In the early 1980s, the Motorola 68012 was introduced; it had 32-bit data and address registers, as did the Motorola 68010, but instead of providing the lower 24 bits of an address, it did so for all but bit 30 on the address pins.
Article summary
In computer architecture, 31-bit integers, memory addresses, or other data units are those that are 31 bits wide. In 1983, IBM introduced 31-bit addressing in the System/370-XA mainframe architecture as an upgrade to the 24-bit physical and virtual, and transitional 24-bit-virtual/26-bit physical, addressing in System/370. This enhancement allowed address spaces to be 128 times larger, permitting programs to address memory above 16 MB (referred to as "above the line"). Support for COBOL, FORTRAN and later on Linux/390 was included. In the early 1980s, the Motorola 68012 was introduced; it had 32-bit data and address registers, as did the Motorola 68010, but instead of providing the lower 24 bits of an address, it did so for all but bit 30 on the address pins.
Key claims
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.