View source for MCP-1600

{{Distinguish|MPC 1600}}
{{Infobox CPU
|name           = Western Digital MCP-1600
|image          = WD16 on AM-100.jpg
|caption        = MCP-1600 microprocessor with WD16 microcode in five 40-pin packages.
|produced-start = {{Start date and age|1975}}
|numinstructions = 98
|produced-end   = 
|data-width     = 8 (microdata), 18 (microcode), 16 (macrodata)
|address-width  = 11 (microcode), 16 (macrodata)
|slowest        = 
|fastest        = 3.3 | fast-unit = MHz
|transistors    = 
|manuf1         = [[Western Digital]]
|pack1          = 4 or 5 x 40-pin [[Dual in-line package|DIP]]
|successor      = none
}}

{| class="infobox" style="font-size:88%;width:34em;"
|+ MCP-1600 registers
|-
| style="text-align:center;"| <sup>1</sup><sub>5</sub>
| style="text-align:center;"| <sup>1</sup><sub>4</sub>
| style="text-align:center;"| <sup>1</sup><sub>3</sub>
| style="text-align:center;"| <sup>1</sup><sub>2</sub>
| style="text-align:center;"| <sup>1</sup><sub>1</sub>
| style="text-align:center;"| <sup>1</sup><sub>0</sub>
| style="text-align:center;"| <sup>0</sup><sub>9</sub>
| style="text-align:center;"| <sup>0</sup><sub>8</sub>
| style="text-align:center;"| <sup>0</sup><sub>7</sub>
| style="text-align:center;"| <sup>0</sup><sub>6</sub>
| style="text-align:center;"| <sup>0</sup><sub>5</sub>
| style="text-align:center;"| <sup>0</sup><sub>4</sub>
| style="text-align:center;"| <sup>0</sup><sub>3</sub>
| style="text-align:center;"| <sup>0</sup><sub>2</sub>
| style="text-align:center;"| <sup>0</sup><sub>1</sub>
| style="text-align:center;"| <sup>0</sup><sub>0</sub>
| ''(bit position)''
|- 16
|colspan="16" | '''Register file''' <br/>
|colspan="1" | LSI-11 use<ref name=":1">{{cite book |last1=Bell |first1=C. Gordon |title=Computer Engineering: A DEC View of Hardware Systems Design |date=1978 |publisher=Digital Equipment Corporation |isbn=1-483207-67-6 |edition=4th Printing |url=http://gordonbell.azurewebsites.net/computer_engineering/contents.html |access-date=29 July 2022}}</ref><br/>
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| R3
| style="text-align:center;" colspan="8"| R2
| style="width:auto; background:white; color:black;"| PSW
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| R5
| style="text-align:center;" colspan="8"| R4
| style="width:auto; background:white; color:black;"| Destination
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| R7
| style="text-align:center;" colspan="8"| R6
| style="width:auto; background:white; color:black;"| Source
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| R9
| style="text-align:center;" colspan="8"| R8
| style="width:auto; background:white; color:black;"| Bus address
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| RB
| style="text-align:center;" colspan="8"| RA
| style="width:auto; background:white; color:black;"| Instruction register
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| RD/GD
| style="text-align:center;" colspan="8"| RC/GC
| style="width:auto; background:white; color:black;"| R7 (PC)
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| RF/GF
| style="text-align:center;" colspan="8"| RE/GE
| style="width:auto; background:white; color:black;"| R6 (SP)
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| GB
| style="text-align:center;" colspan="8"| GA
| style="width:auto; background:white; color:black;"| R5
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| G9
| style="text-align:center;" colspan="8"| G8
| style="width:auto; background:white; color:black;"| R4
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| G7
| style="text-align:center;" colspan="8"| G6
| style="width:auto; background:white; color:black;"| R3
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| G5
| style="text-align:center;" colspan="8"| G4
| style="width:auto; background:white; color:black;"| R2
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| G3
| style="text-align:center;" colspan="8"| G2
| style="width:auto; background:white; color:black;"| R1
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| G1
| style="text-align:center;" colspan="8"| G0
| style="width:auto; background:white; color:black;"| R0
|- 
|colspan="17" | '''Control registers''' <br/>
|- style="background:silver;color:black"
| style="text-align:center; background:white" colspan="13" | &nbsp;
| style="text-align:center;" colspan="3"| G
| style="background:white; color:black;"| Register Pointer
|- 
|- style="background:silver;color:black"
| style="text-align:center; background:white" colspan="5" | &nbsp;
| style="text-align:center;" colspan="11"| LC
| style="background:white; color:black;"| Location Counter
|-
|- style="background:silver;color:black"
| style="text-align:center; background:white" colspan="5" | &nbsp;
| style="text-align:center;" colspan="11"| RR
| style="background:white; color:black;"| Return Register
|- 
|- style="background:silver;color:black"
| style="text-align:center;" colspan="8"| TR1
| style="text-align:center;" colspan="8"| TR0
| style="background:white; color:black;"| Translation Register
|- 
|colspan="17" | '''Status register'''
|- style="background:silver;color:black"
| style="text-align:center; background:white" colspan="8" | &nbsp;
| style="text-align:center;"| NB
| style="text-align:center;"| ZB
| style="text-align:center;"| C4
| style="text-align:center;"| C8
| style="text-align:center;"| N
| style="text-align:center;"| Z
| style="text-align:center;"| V
| style="text-align:center;"| C
| style="background:white; color:black" | ALU status/Flags
|}

The '''MCP-1600''' is a multi-chip [[16-bit]] [[microprocessor]] introduced by [[Western Digital]] in 1975 and produced through the early 1980s.<ref>{{cite journal |title=Western Digital adds MCP-1600 Micro |journal=Computerworld |date=26 November 1975 |url=https://books.google.com/books?id=nMHHJQxdDHYC&pg=RA1-PA26}}</ref><ref>{{cite web|url=http://www.antiquetech.com/?page_id=782|title=Western Digital 1600|publisher=AntiqueTech|accessdate=5 January 2017|archive-url=https://web.archive.org/web/20170103021205/http://www.antiquetech.com/?page_id=782|archive-date=3 January 2017|url-status=dead}}</ref> Used in the [[Pascal MicroEngine]], the [[Western Digital WD16|WD16]] processor in the [[Alpha Microsystems]] AM-100, and the [[Digital Equipment Corporation|DEC]] [[PDP-11#LSI-11|LSI-11]] microcomputer,<ref>{{cite journal |title=Western & DEC have 3-Chip uC Mini |journal=Microcomputer Digest |date=December 1974 |volume=1 |issue=6 |page=7 |url=http://www.bitsavers.org/magazines/Microcomputer_Digest/Microcomputer_Digest_v01n06_Dec74.pdf |access-date=11 January 2023}}</ref> a cost-reduced and compact implementation of the DEC [[PDP-11]].

== Description ==

There are three types of chips in the chip-set:
* CP1611 RALU - Register [[Arithmetic logic unit|ALU]] chip
* CP1621 CON - Control chip
* CP1631 MICROM - Mask-programmed [[microcode]] [[Read-only memory|ROM]] chip (512 &ndash; 22 bit words)

The chips use a 3.3[[MHz]] [[clock signal#4-phase clock|four phase clock]] and three power supply voltages (+5V, +12V, and -5V), as required by the [[N-channel]] [[Self-aligned gate|silicon gate]] process then available at Western Digital. Internally the MCP-1600 is a (relatively fast) 8-bit processor that can be micro-programmed to emulate a 16-bit CPU. All byte operations execute in one clock period; word operations and branches take two clocks. Up to four MICROMs are supported, but usually two or three could hold the needed microprogram for a processor.<ref name=":0">{{cite book |title=MCP-1600 Microprocessor Users Manual |date=1975 |publisher=Western Digital |url=http://bitsavers.trailing-edge.com/pdf/westernDigital/MCP-1600/MCP-1600_Users_Manual_Oct77.pdf |access-date=28 April 2022}}</ref> 

The register file consists of 26 8-bit registers. Ten may be addressed directly by the microinstruction (Rx), four may be addressed either directly or indirectly (Rx/Gx), and the remaining 12 may be addressed only indirectly (Gx). Indirect addressing is via a 3-bit G register which is usually loaded with the register field of the PDP-11 instruction.<ref name=":1" />

The most significant feature of the MCP-1600 is its Programmable Translation Array (PTA). The PTA serves to generate new microinstruction fetch addresses as a function of several parameters. These parameters are those which are normally considered during the decode of a macroinstruction. The PTA was designed specifically to eliminate most of the overhead of macroinstruction translation. Essentially a macroinstruction opcode is quickly translated into an address that is loaded onto the Location Counter, creating a jump to the appropriate microcode to handle the macroinstruction.<ref name=":0" />

John Wallace was the Project Manager and designed the 1621, Mike Briner designed the 1611, and later became a Senior VP at [[Silicon Storage Technology]].  Bill Pohlman was the design engineering manager and he later was Project Manager for the [[Intel 8086]] processor.

Microcode could be developed using a [[Digital Equipment Corporation|DEC]] [[LSI-11]] computer with the KUV11-AA [[Writable control store|Writable Control Store]] (WCS) option. This option allowed programming of the internal 8-bit micromachine to create application-specific extensions to the instruction set. The WCS is a quad [[Q-Bus]] board with a ribbon cable connecting to an open MCP-1600 microcode ROM socket.<ref>{{cite book |title=LSI-11 WCS user's guide |date=June 1978 |publisher=Digital Equipment Corporation |edition=1st |url=http://www.bitsavers.org/pdf/dec/pdp11/1103/EK-KUV11-TM_LSI11_WCS.pdf |access-date=7 January 2023 |archive-date=23 February 2023 |archive-url=https://web.archive.org/web/20230223212303/http://www.bitsavers.org/pdf/dec/pdp11/1103/EK-KUV11-TM_LSI11_WCS.pdf |url-status=live }}</ref>

In January 1976, the three-chip minimum MCP-1600 configuration was offered at $159 (${{Inflation|US|159|1976|r=-1}} in {{Inflation/year|US}}) in 100-999 quantities.<ref>{{cite journal |title=Three-chip set holds 16-bit microprocessor |journal=Electronic Design |date=January 5, 1976 |volume=24 |issue=1 |page=61 |url=https://www.worldradiohistory.com/Archive-Electronic-Design/1976/Electronic-Design-V24-N01-1976-0105.pdf |access-date=6 January 2025}}</ref> In March 1976, it was announced that [[National Semiconductor]] would second-source the MCP-1600. It is unclear whether any were produced by National.<ref>{{cite journal |title=MCP 1600 Second Sourced |journal=Modern Data |date=March 1976 |volume=9 |issue=3 |page=40 |url=https://archive.decromancer.ca/bitsavers.org/magazines/Modern_Data/Modern_Data_1976_03.pdf |access-date=7 November 2022}}</ref>

A clone of the CP1611 and CP1621 was manufactured in the [[Soviet Union]] under the [[Soviet integrated circuit designation|designation]] KR581IK1 and KR581IK2 ({{langx|ru|[[:ru:К581|КР581ИК1]] and КР581ИК2|italic=yes}}).<ref name=cpuworld>{{cite web
| title=Soviet microprocessors, microcontrollers, FPU chips and their western analogs
| publisher=CPU-world
| url=http://www.cpu-world.com/info/exUSSR-chips.html
| accessdate=2020-04-18
}}</ref> The Soviet 581 series included other members of the MCP-1600 family as well.<ref name=kozak>{{cite web
| first=Виктор Романович
| last=Козак
| title= Номенклатура интегральных микросхем — Микропроцессоры: серии 580 - 589
| trans-title=Nomenclature of integrated circuits — Microprocessors: Series 580 - 589
| url=http://www.inp.nsk.su/~kozak/adv/advh1.htm
| language=Russian
| date=24 May 2014
| accessdate=24 March 2016
}}</ref>

==Simulator==
''cp16sim'' is an open source MCP-1600 simulator. Written in [[C (programming language)|C]], it emulates the MCP-1600 processor and its PTA executing the code found on the WD9000 Pascal Microengine processor. As of 2016 it is unfinished. "It works well enough to execute the first few dozen p-code instructions of the ACD PDQ-3 boot ROM before going into the weeds." It is released under the [[GNU General Public License]] version 3.<ref>{{cite web |last1=Smith |first1=Eric |title=Microcode-Level Simulator for Western Digital MCP1600 |url=https://github.com/brouhaha/cp16sim |website=Github |access-date=25 December 2022}}</ref>

==Gallery==
<gallery caption="Die photos from LSI-11 chip set" mode="packed" heights="200px">
Image:Western_Digital_1611_die.JPG|CP1611 RALU chip
Image:Western_Digital_2007_die.JPG|CP1621 Control chip
Image:Western_Digital_3010_die.JPG|CP1631 MICROM chip
</gallery>

==References==
{{reflist}}

{{Western Digital}}

[[Category:16-bit microprocessors]]
[[Category:Western Digital products]]