Talk:Accumulator (computing)

Latest comment: 3 years ago by Chatul in topic What is "early"

Massive rework needed

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This is bad, really bad.

First of all this article suggests an accumulator processors has one accumulator (which 6502 did). However numerous examples are contrary to this such as

  • 6809 has accumulators A and B that could be concatenated to D, 6308 had even more
  • 56300 has again 2 large accumulators of extended width
  • 96000 also has 2 accumulators that are even wider

With 2 accumulators you need only a single bit in the instruction to indicate what accumulator is to be used. 68000 has a lot of data registers, and those are not called accumulators, so the article should state clearly where the limit is. Seems the limit is around 4 (ARM Piccolo)

SWEET16 has one accumulator and 15 other registers, a wealth closer to 68000.

Next is the link to accumulator-based architecture which goes to PDP-8, specifically the section Legacy_of_accumulator-based_architectures which no longer exists. Is there any reason why this has to be split up?

Also it seems a bit lacking that the multiply-and-accumulate is not mentioned.

All in all an article in need of an overhaul. --22:47, 22 February 2009 (UTC) Amended --21:30, 23 February 2009 (UTC)

Hopefully such an overhaul will also disambiguate further, since the term "accumulator" in programming applies to a variable in which values are accumulated... 63.249.90.205 (talk) 00:55, 25 June 2010 (UTC)Reply

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What is "early"

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#Accumulator machines says Almost all early computers were accumulator machines with only the high-performance "supercomputers" having multiple registers. However, the IBM 7070[1] had three accumulators, the UNIVAC 1107[2][a] had 16, the DEC PDP-6[3][b] had 16 and, of course, the IBM System/360 had 16 general registers. The 1107, PDP-6, S/360 and their successors were popular in the 1960s and 1970s, and that era was dominated by machines with multiple accumulators. So where is the cutoff for "early"? --Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:54, 25 July 2021 (UTC)Reply

The IBM 702 apparently had two accumulators, A and B, according to page 17 of the preliminary 702 reference manual, althoug the 705 had 1. And the IBM 1401 has, err, umm, zero? I haven't looked at other vendors' decimal machines. Guy Harris (talk) 23:45, 25 July 2021 (UTC)Reply
@Guy Harris:The 705 actually had 16 accumulators, although IBM referred to the smaller ones as Auxiliary Storage Units (ASUs). Of the IBM machines prior to the S/360, only the 702, 705, 7070 and 7080 had multiple accumulators, although there were machines with both an accumulator and a Multiplier-Quotient register, or equivalent.
It was common for character-oriented machines to be storage-to-storage with no accumulator, as in the 1401/1440/1460/1410/7010 and the RCA 301/3301.
Other vendors' decimal machines followed the same pattern; either word with single accumulator or character with no accumulator. --Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:32, 26 July 2021 (UTC)Reply

Notes

  1. ^ Sperry Rand called them arithmetic registers or A-registers.
  2. ^ Storage locations 0-15 served as both accumulators and index registers.

References

  1. ^ Reference Manual IBM 7070 Data Processing System (PDF) (Second ed.). IBM. January 1960. A22-7003-01.
  2. ^ Technical Bulletin Bulletin UNIVAC 1107 Central Computer (PDF). Remington Rand Univac division of Sperry Rand. November 1961. UT-2463.
  3. ^ Programmed Data Processor-6 Handbook (PDF). DEC. August 1964. F65.