Talk:Accumulator (computing)

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This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

Massive rework needed

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"

#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

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

References

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

[3] Sperry Rand called them arithmetic registers or A-registers.

[5] Storage locations 0-15 served as both accumulators and index registers.

[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.

[4] Programmed Data Processor-6 Handbook (PDF). DEC. August 1964. F65.

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