Bendix G-15 - Revision history

Jnc: /* External links */ +one from Paul Allen's collection at the LCM

2025-04-22T15:16:21Z

‎External links: +one from Paul Allen's collection at the LCM

Jnc: /* Further reading */ typo

2024-12-06T01:24:04Z

‎Further reading: typo

Jnc: /* Further reading */ link AHC

2024-12-06T01:17:10Z

‎Further reading: link AHC

Jnc: It was built out of vacuum tubes

2024-04-01T20:44:31Z

It was built out of vacuum tubes

Jnc: Possibly ancestor of Packard Bell PB 250?

2024-04-01T08:53:27Z

Possibly ancestor of Packard Bell PB 250?

Jnc: /* Internals */ Correct how short tracks work

2024-03-25T01:49:34Z

‎Internals: Correct how short tracks work

Jnc: After much sifting of hard-to-comprehend documentation, here is a reasonable executive summary

2024-03-25T00:22:46Z

After much sifting of hard-to-comprehend documentation, here is a reasonable executive summary

New page

The '''Bendix G-15''' was an early low-cost (and thus low-performance) [[computer]], produced by Bendix Computer Division (later bought by [[Control Data]]), from a design by Harry Huskey. His design was based on the [[Automatic Computing Engine|ACE]], on which Huskey had worked while he was in the UK. It was first delivered in 1956; around 400 were sold (legend has it that the last one went to Harry Huskey personally).

It was a [[serial]] machine, which used a [[drum]] for its [[main memory]]; like the ACE on which it was based, it was capable of [[optimum programming]]. The drum rotated at 1500 RPM, and held 20 'long' [[track]]s, each containing 108 words, which were 29 [[bit]]s wide; the words within a track were numbered with 'timing numbers'. The G-15 could perform 1,850 additions per second.

Standard [[input/output]] equipment included an electric typewriter, and a [[paper tape]] reader and punch; up to 4 [[magnetic tape drive]]s were available as an option, along with a [[punched card]] reader and punch. A [[digital]] [[differential analyzer]] was available as a [[co-processor]] for solving certain types of problems.

==Internals==

The G-15's [[instruction]]s were also 29 bits wide. They contained 8 fields:

{| class="wikitable"
! Field Name !! Width !! Description
|-
| SD || 1 || Single- or double-length
|-
| D || 5 || Destination; track where result is to be stored
|-
| S || 5 || Source; track holding source [[operand]]
|-
| CH || 2 || Characteristic; selected behaviour of transfers
|-
| N || 7 || Next; timing number of next instruction
|-
| B || 1 || Breakpoint
|-
| T || 7 || Transfer timing number
|-
| ID || 1 || Deferred instruction (if '1')
|}

For operands in long tracks, the timing number used was selected by the 'Transfer' field. Instructions contained up to ''3'' [[address]]es; a source, a destination, and the address of the next instruction. (The G-15 had no [[Program Counter]].) The 'next' instruction was in the same track (hence only its timing number is given); control could be passed to a different track (the equivalent of a [[jump]]) with a specific instruction.

Note that there is no [[operation code]] in the instruction; instead, combinations of certain source and destination values and characteristics had side-effects. (A complete list may be found on pg. 7 of the 'Coding Manual for the Bendix G-15', below.)

In addition to the 20 long tracks, the drum also had 4 quad-word lines, 3 double-word lines (for double-length [[operand]]s, the "ID = 'cand denominator, MQ = multiplier quotient, and PN = product numerator" - the G-15 had hardware multiplication and division), and 1 single-word line (the accumulator, AR). The shorter ones had the role of [[register]]s in most computers, and came with lower [[access time]]s); to achieve that, they were replicated around the track, with multiple pairs of [[head]]s.

Having a [[breakpoint]] bit in every instruction simplified [[debug]]ging; no prior preparation was needed, to begin at any point in time.

==Further reading==

* Harry D. Huskey, David C. Evans, [http://www.bitsavers.org/pdf/bendix/g-15/G-15_WESCON_Aug54.pdf ''The Bendix G-15 General Purpose Computer''] - the best of a bad lot, as far as comprehensible documentation goes
* Harry D. Huskey, Granino A. Korn, (editors), ''Computer Handbook'', McGraw-Hill, New York, 1962 - the G-15 is covered on pp. 20-15—20-19
* Harry D. Huskey, ''From ACE to the G-15'', Annals of the History of Computing, Vol. 6, No. 4, Oct0ber, 1984, pp. 350-371

==External links==

* [http://www.bitsavers.org/pdf/bendix/g-15/ G-15] - documentation at [[Bitsavers]]
** [http://www.bitsavers.org/pdf/bendix/g-15/G15_CodingManual.pdf Coding Manual for the Bendix G-15]
** [http://www.bitsavers.org/pdf/bendix/g-15/G15D_Programmers_Ref_Man.pdf G15D Programmer's Reference Manual]
** [http://www.bitsavers.org/pdf/bendix/g-15/60121600_G15_Theory_Of_Operation_Nov64.pdf Theory of Operation and Simplified Drawings for {the} G-15 Computer]
* [https://www.computerhistory.org/revolution/early-computer-companies/5/115 From Airplane Parts to Computers: The Bendix G-15]
** [https://www.computerhistory.org/revolution/early-computer-companies/5/115/491 Bendix G-15] - brochure
** [https://www.computerhistory.org/revolution/early-computer-companies/5/115/1506 Bendix G-15] - includes several images
* [http://archive.computerhistory.org/resources/text/Bendix/Bendix.G-15.1955.102646277.pdf Bendix G-15] - brochure
* [http://s3data.computerhistory.org/brochures/bendix.g15.1956.102646144.pdf Bendix G-15 All-Purpose Computer]
** [http://s3data.computerhistory.org/brochures/bendix.g15auto.1956.102621696.pdf Bendix G-15 Automatic Programming Systems]
* [https://rbk.delosent.com/g15doc.html Bendix G-15 Documentation] - a very large amount of material
* [https://web.archive.org/web/20060719065651/http://members.iinet.com.au/~dgreen/ The First Generation Computers - Bendix G-15 Computer]
** [https://web.archive.org/web/20061105152639/http://members.iinet.com.au/~dgreen/docs.html The Bendix G-15 General Purpose Digital Computer System Documentation]
* [https://ed-thelen.org/comp-hist/g-15.html Bendix G-15]
* [http://www.piercefuller.com/collect/bendix/ Bendix G15]
* [https://www.historyofinformation.com/detail.php?id=5128 Harry Huskey Designs the Bendix G-15, the First Mini-Computer]
* [https://www.livingcomputers.org/Blog/Bendix-G-15-Vacuum-Tubes.aspx Bendix G-15 Vacuum Tubes]
* [https://www.livingcomputers.org/Blog/Bendix-G-15-%E2%80%93-Solder-Degradation.aspx Bendix G-15 – Solder Degradation]
* [https://www.rrauction.com/auctions/lot-detail/347709906735051-bendix-g-15-the-first-mini-computer-the-third-built-in-1956 Bendix G-15, the First Mini-Computer] - sale of G-15 serial #3; many images

[[Category: Early Computers]]

@@ Line 43: / Line 43: @@
 * Harry D. Huskey, David C. Evans, [http://www.bitsavers.org/pdf/bendix/g-15/G-15_WESCON_Aug54.pdf ''The Bendix G-15 General Purpose Computer''] - the best of a bad lot, as far as comprehensible documentation goes
 * Harry D. Huskey, Granino A. Korn, (editors), ''Computer Handbook'', McGraw-Hill, New York, 1962 - the G-15 is covered on pp. 20-15&mdash;20-19
-* Harry D. Huskey, ''From ACE to the G-15'', [[Annals of the History of Computing]], Vol. 6, No. 4, Oct0ber, 1984, pp. 350-371
+* Harry D. Huskey, ''From ACE to the G-15'', [[Annals of the History of Computing]], Vol. 6, No. 4, October, 1984, pp. 350-371
 ==External links==

← Older revision		Revision as of 08:53, 1 April 2024
Line 4:		Line 4:

	Standard [[input/output]] equipment included an electric typewriter, and a [[paper tape]] reader and punch; up to 4 [[magnetic tape drive]]s were available as an option, along with a [[punched card]] reader and punch. A [[digital]] [[differential analyzer]] was available as a [[co-processor]] for solving certain types of problems.		Standard [[input/output]] equipment included an electric typewriter, and a [[paper tape]] reader and punch; up to 4 [[magnetic tape drive]]s were available as an option, along with a [[punched card]] reader and punch. A [[digital]] [[differential analyzer]] was available as a [[co-processor]] for solving certain types of problems.
		+
		+	Some sources consider the [[Packard Bell PB 250]] to be a descendant of the G-15, but the strength of the connection (if any) is not yet known.

	==Internals==		==Internals==

@@ Line 66: / Line 66: @@
 * [https://www.livingcomputers.org/Blog/Bendix-G-15-%E2%80%93-Solder-Degradation.aspx Bendix G-15 – Solder Degradation]
 * [https://www.rrauction.com/auctions/lot-detail/347709906735051-bendix-g-15-the-first-mini-computer-the-third-built-in-1956 Bendix G-15, the First Mini-Computer] - sale of G-15 serial #3; many images
 [[Category: Early Computers]]

@@ Line 1: / Line 1: @@
 The '''Bendix G-15''' was an early low-cost (and thus low-performance) [[computer]], produced by Bendix Computer Division (later bought by [[Control Data]]), from a design by Harry Huskey. His design was based on the [[Automatic Computing Engine|ACE]], on which Huskey had worked while he was in the UK. It was first delivered in 1956; around 400 were sold (legend has it that the last one went to Harry Huskey personally).
-It was a [[serial]] machine, which used a [[drum]] for its [[main memory]]; like the ACE on which it was based, it was capable of [[optimum programming]]. The drum rotated at 1500 RPM, and held 20 'long' [[track]]s, each containing 108 words, which were 29 [[bit]]s wide; the words within a track were numbered with 'timing numbers'. The G-15 could perform 1,850 additions per second.
+It was a [[serial]] machine, which used a [[drum]] for its [[main memory]]; like the ACE on which it was based, it was capable of [[optimum programming]]. The drum rotated at 1500 RPM, and held 20 'long' [[track]]s, each containing 108 words, which were 29 [[bit]]s wide; the words within a track were numbered with 'timing numbers'. The [[logic]] was built out of [[vacuum tube]]s; the G-15 could perform 1,850 additions per second.
 Standard [[input/output]] equipment included an electric typewriter, and a [[paper tape]] reader and punch; up to 4 [[magnetic tape drive]]s were available as an option, along with a [[punched card]] reader and punch. A [[digital]] [[differential analyzer]] was available as a [[co-processor]] for solving certain types of problems.

@@ Line 33: / Line 33: @@
 Note that there is no [[operation code]] in the instruction; instead, combinations of certain source and destination values and characteristics had side-effects. (A complete list may be found on pg. 7 of the 'Coding Manual for the Bendix G-15', below.)
-In addition to the 20 long tracks, the drum also had 4 quad-word lines, 3 double-word lines (for double-length [[operand]]s, the "ID = 'cand denominator, MQ = multiplier quotient, and PN = product numerator" - the G-15 had hardware multiplication and division), and 1 single-word line (the accumulator, AR). The shorter ones had the role of [[register]]s in most computers, and came with lower [[access time]]s); to achieve that, they were replicated around the track, with multiple pairs of [[head]]s.
+In addition to the 20 long tracks, the drum also had 4 quad-word lines, 3 double-word lines (for double-length [[operand]]s, the "ID = 'cand denominator, MQ = multiplier quotient, and PN = product numerator" - the G-15 had hardware multiplication and division), and 1 single-word line (the accumulator, AR). The shorter ones had the role of [[register]]s in most computers, and came with lower [[access time]]s); to achieve that, the read and write [[head]]s were placed closer together around the circumference of the track.
 Having a [[breakpoint]] bit in every instruction simplified [[debug]]ging; no prior preparation was needed, to begin at any point in time.