PDP-4 - Revision history

Jnc: /* External links */ +DEC marketing brochure

2024-02-07T18:00:04Z

‎External links: +DEC marketing brochure

Larsbrinkhoff: Basic instruction set.

2023-07-20T19:03:06Z

Basic instruction set.

Larsbrinkhoff: 18-bit cat.

2023-07-11T11:39:03Z

18-bit cat.

Jnc: /* External links */ +manual

2022-08-06T21:21:21Z

‎External links: +manual

Jnc: link to relevant chapter in 'Computer Engineering'

2021-12-08T23:34:11Z

link to relevant chapter in 'Computer Engineering'

Jnc: standard naming system

2021-05-22T18:38:26Z

standard naming system

Jnc: +DEC nav bar

2021-05-18T21:48:09Z

+DEC nav bar

Jnc: A few more details

2021-05-12T22:34:32Z

A few more details

Jnc: Fairly complete

2021-05-12T21:07:18Z

Fairly complete

New page

{{Infobox Machine
| name = PDP-4
| manufacturer = [[Digital Equipment Corporation|DEC]]
| year introduced = 1962
| form factor = [[minicomputer]]
| word size = 18 bits
| physical address = 15 bits (32K words - requires Type 16 Memory Extension Control)
| virtual address = 13 bits
| logic type = germanium [[transistor]] [[System Module]]s


| memory speed = 2 μsec ([[access time]])<br>8 μsec (read/write [[cycle time]])


| predecessor = [[PDP-1]]
| successor = [[PDP-7]]
| price = US$65K


}}

The '''PDP-4''' was a [[minicomputer]] produced by [[Digital Equipment Corporation]]; DEC's second production computer, and another 18-bit machine, like its predecessor, the [[PDP-1]]. It too had a [[load-store architecture]], with a single [[accumulator]] and a directly-accessible link (carry) bit. Introduced in 1962, it was originally intended principally for [[process control]] applications; approximately 54 were sold.

The [[instruction set]], although similar to that of the PDP-1, was simplified; removing less-used complexity allowed it to be physically smaller (less than half the size) and cheaper (roughly half the cost) than its predecessor. PDP-1 [[main memory]] and [[peripheral]]s could be used on the PDP-4, though.

The PDP-4A included 1KW of [[core memory|core]] main memory; the PDP-4B had 4KW, but was otherwise identical. A Type 17 (later Type 134) Core Memory Module added another 4KW to a PDP-4B; after that, a Type 16 Core Memory Extension Control allowed use of up to three additional 8KW Type 135 Core Memory Modules.

The optional Type 18 (later Type 22) [[Extended Arithmetic Element]] added 23 [[instruction]]s to facilitate high speed multiplication, division, [[normalization]] and shifting. "The EAE contains an 18-bit register, the Multiplier Quotient (MQ); a 6-bit register, the Step Counter (SC); and a 3-bit Instruction Register."

Standard peripherals included a [[paper tape]] reader. Optional peripherals included a [[terminal]] (a [[Teletype]] Model 28), several different [[graphics]] [[display]]s, a [[light pen]], [[line printer]], paper tape punch, [[punched card]] reader and punch, and [[magnetic tape]] [[device controller|controller]] and [[magnetic tape drive|drives]]. The Type 24 [[magnetic storage|Magnetic]] [[Drum]] System could hold either 16KW, 32KW or 64KW of [[secondary storage]].

==Technical details==

The instruction format consisted of a 4-bit basic operation code, a 1-bit indirect address bit, and a 13-bit memory address. The augmented instructions all share an operation code. In them, the address field is not used for an address; instead, each bit of the field can specify a separate operation, and generally more than one bit can be set at a time (except for most of the [[skip]] operations). The [[Program Counter]] is also 13 bits long.

The PDP-4 supported both [[one's complement]] and [[two's complement]] number representations; the latter was better for [[extended precision]] calculations.

It was constructed out of 4000-Series [[System Module]]s, which used germanium [[transistor]]s.

==Further reading==

* C. Gordon Bell, J. Craig Mudge, John. E. McNamara, "''Computer Engineering: A DEC View of Hardware Systems Design''" (Digital Press, Bedford, 1978) - The PDP-4 is covered in Chapter 6
* "''PDP-4 Manual''", F-45, Digital Equipment Corporation, 1962

==External links==

* [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents

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[[Category: DEC Systems]]

@@ Line 87: / Line 87: @@
 * [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents
 * [https://gordonbell.azurewebsites.net/Digital/PDP%204%20Manual%201962.pdf PDP-4 Manual, 1962]
 * C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, [http://gordonbell.azurewebsites.net/Computer_Engineering/00000163.htm The PDP-1 and Other 18-Bit Computers], in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, ''Computer Engineering: A DEC View of Hardware Systems Design'', Digital Press, Bedford, 1978

@@ Line 40: / Line 40: @@
 It was constructed out of 4000-Series [[System Module]]s, which used  germanium [[transistor]]s.
-{{semi-stub}}
+==Instruction set==
 ==Further reading==
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 * [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents
 * [https://gordonbell.azurewebsites.net/Digital/PDP%204%20Manual%201962.pdf PDP-4 Manual, 1962]
 * C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, [http://gordonbell.azurewebsites.net/Computer_Engineering/00000163.htm The PDP-1 and Other 18-Bit Computers], in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, ''Computer Engineering: A DEC View of Hardware Systems Design'', Digital Press, Bedford, 1978

← Older revision		Revision as of 11:39, 11 July 2023
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	[[Category: DEC Systems]]		[[Category: DEC Systems]]
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← Older revision		Revision as of 21:21, 6 August 2022
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	* [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents		* [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents
		+	* [https://gordonbell.azurewebsites.net/Digital/PDP%204%20Manual%201962.pdf PDP-4 Manual, 1962]
	* C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, [http://gordonbell.azurewebsites.net/Computer_Engineering/00000163.htm The PDP-1 and Other 18-Bit Computers], in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, ''Computer Engineering: A DEC View of Hardware Systems Design'', Digital Press, Bedford, 1978		* C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, [http://gordonbell.azurewebsites.net/Computer_Engineering/00000163.htm The PDP-1 and Other 18-Bit Computers], in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, ''Computer Engineering: A DEC View of Hardware Systems Design'', Digital Press, Bedford, 1978

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 It was constructed out of 4000-Series [[System Module]]s, which used  germanium [[transistor]]s.
 ==Further reading==
 * "''PDP-4 Manual''", F-45, Digital Equipment Corporation, 1962
@@ Line 48: / Line 49: @@
 * [http://www.bitsavers.org/pdf/dec/pdp4/ PDP-4] - Original PDP-4 documents
+* C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, [http://gordonbell.azurewebsites.net/Computer_Engineering/00000163.htm The PDP-1 and Other 18-Bit Computers], in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, ''Computer Engineering: A DEC View of Hardware Systems Design'', Digital Press, Bedford, 1978
 {{Nav DEC}}
 [[Category: DEC Systems]]

@@ Line 3: / Line 3: @@
 | manufacturer = [[Digital Equipment Corporation|DEC]]
 | year introduced = 1962
-| form factor = [[minicomputer]]
+| form factor = small computer
 | word size = 18 bits
 | physical address = 15 bits (32K words - requires Type 16 Memory Extension Control)
@@ Line 20: / Line 20: @@
 }}
-The '''PDP-4''' was a [[minicomputer]] produced by [[Digital Equipment Corporation]]; DEC's second production computer, and another 18-bit machine, like its predecessor, the [[PDP-1]]. It too had a [[load-store architecture]], with a single [[accumulator]] and a directly-accessible link (carry) bit. Introduced in 1962, it was originally intended principally for [[process control]] applications; approximately 54 were sold.
+The '''PDP-4''' was a small computer produced by [[Digital Equipment Corporation]]; DEC's second production computer, and another 18-bit machine, like its predecessor, the [[PDP-1]]. It too had a [[load-store architecture]], with a single [[accumulator]], and a directly-accessible link (carry) bit. Introduced in 1962, it was originally intended principally for [[process control]] applications; approximately 54 were sold.
-The [[instruction set]], although similar to that of the PDP-1, was simplified; removing less-used complexity allowed it to be physically smaller (less than half the size) and cheaper (roughly half the cost) than its predecessor. PDP-1 [[main memory]] and [[peripheral]]s could be used on the PDP-4, though.
+The [[instruction set]], although similar to that of the PDP-1, was simplified; removing less-used complexity allowed it to be physically smaller (less than half the size) and cheaper (roughly half the cost) than its predecessor. The resultant machine had 5/8 the performance of the PDP-1, but the differential was not large enough to boost sales to the hoped-for level. PDP-1 [[main memory]] and [[peripheral]]s could be used on the PDP-4, though.
-The PDP-4A included 1KW of [[core memory|core]] main memory; the PDP-4B had 4KW, but was otherwise identical. A Type 17 (later Type 134) Core Memory Module added another 4KW to a PDP-4B; after that, a Type 16 Core Memory Extension Control allowed use of up to three additional 8KW Type 135 Core Memory Modules.
+The PDP-4A included 1KW of [[core memory|core]] main memory; the PDP-4B had 4KW, but was otherwise identical. A Type 17 (later Type 134) Core Memory Module added another 4KW to a PDP-4B; after that, a Type 16 Core Memory Extension Control allowed (via [[bank switching]]) use of up to three additional 8KW Type 135 Core Memory Modules.
 The optional Type 18 (later Type 22) [[Extended Arithmetic Element]] added 23 [[instruction]]s to  facilitate high speed multiplication, division, [[normalization]] and shifting. "The EAE contains an 18-bit register, the Multiplier Quotient (MQ); a 6-bit register, the Step Counter (SC); and a 3-bit Instruction Register."
@@ Line 34: / Line 34: @@
 The instruction format consisted of a 4-bit basic operation code, a 1-bit indirect address bit, and a 13-bit memory address. The augmented instructions all share an operation code. In them, the address field is not used for an address; instead, each bit of the field can specify a separate operation, and generally more than one bit can be set at a time (except for most of the [[skip]] operations). The [[Program Counter]] is also 13 bits long.
-The PDP-4 supported both [[one's complement]] and [[two's complement]] number representations; the latter was better for [[extended precision]] calculations.
+The PDP-4 supported both [[one's complement]] and [[two's complement]] number representations; the latter was better for [[multiple precision]] calculations. When used with indirect addressing, memory locations 010-017 were auto-incrementing; this allowed leaving out [[index register]] functionality.
 It was constructed out of 4000-Series [[System Module]]s, which used  germanium [[transistor]]s.