Agnus
Encyclopedia
The MOS Technology
"Agnus", usually called Agnus is an integrated circuit
in the custom chipset
of the Commodore Amiga computer. The Agnus, Denise and Paula chips collectively formed the OCS
and ECS
chipsets.
The Agnus is the Address Generator Chip. Its main function, in chip area, is the RAM
Address Generator and Register Address Encoder which handles all DMA
addresses. The 8361 Agnus is made up of approximately 21000 transistor
s and contains DMA Channel Controllers. The Blitter and Copper are also contained here.
Agnus features:
Agnus was replaced by Alice in the Amiga 4000
and Amiga 1200
when the AGA
chipset was introduced in 1992.
* Somewhere 8372A Agnus mentioned as simply "8372".
Notes
Fat Agnus 1MB and Fat Agnus 2MB usually known as Super Agnus; Super Fat Agnus; Fatter Agnus; Big Agnus; Big Fat Agnus; Super Fat Agnus, but these aren't official names.
References: A500 Service Training, A3000 Service Manual, A500+ Service Manual, A1200 schematics
MOS Technology
MOS Technology, Inc., also known as CSG , was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor, and various designs for Commodore International's range of home computers.-History:MOS Technology, Inc...
"Agnus", usually called Agnus is an integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
in the custom chipset
Chipset
A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...
of the Commodore Amiga computer. The Agnus, Denise and Paula chips collectively formed the OCS
Original Amiga chipset
The Original Chip Set was a chipset used in the earliest Commodore Amiga computers and defined the Amiga's graphics and sound capabilities...
and ECS
Enhanced Chip Set
The Enhanced Chip Set is the second generation of the Amiga computer's chipset, offering minor improvements over the original chipset design. ECS was introduced in 1990 with the launch of the Amiga 3000. Amigas produced from 1990 onwards featured a mix of OCS and ECS chips, such as later versions...
chipsets.
The Agnus is the Address Generator Chip. Its main function, in chip area, is the RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
Address Generator and Register Address Encoder which handles all DMA
Direct memory access
Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
addresses. The 8361 Agnus is made up of approximately 21000 transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s and contains DMA Channel Controllers. The Blitter and Copper are also contained here.
Agnus features:
- The Blitter, a BitmapRaster graphicsIn computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...
image manipulator. The Blitter is capable of copying blocks of display data, or any arbitrary data in the on-board memory, at high speed with various raster operations as well as drawing pixel perfect lines and filling outlined polygons, while freeing the CPU for concurrent tasks. - "Copper" a display synchronized co-processor.
- 25 Direct Memory AccessDirect memory accessDirect memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
(DMA) channels, allowing graphics, sound and I/O to be used with minimal CPU intervention. - DRAMDramDram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
refresh controller. - Memory controller (Memory that can be accessed by the processor and the chipset)
- Generates the system clock from the 28 MHz oscillator
- Video timing.
Agnus was replaced by Alice in the Amiga 4000
Amiga 4000
The Commodore Amiga 4000, or A4000, is the successor of the A2000 and A3000 computers. There are two models, the A4000/040 released in October 1992 with a Motorola 68040 CPU, and the A4000/030 released in April 1993 with a Motorola 68EC030....
and Amiga 1200
Amiga 1200
The Amiga 1200, or A1200 , was Commodore International's third-generation Amiga computer, aimed at the home market...
when the AGA
Advanced Graphics Architecture
Advanced Graphics Architecture is the third generation Amiga graphic chip set, first used in the Amiga 4000 in 1992. AGA was codenamed the Pandora chipset by Commodore International internally....
chipset was introduced in 1992.
Chips by capability
- OCS Agnus which can address up to 512 KB of Chip RAMChip RAMChip RAM is a commonly used term for the integrated RAM used in Commodore's line of Amiga computers. Chip RAM is shared between the central processing unit and the Amiga's dedicated chipset...
(PLCC versions add 512 KB of pseudo-fast RAM)- 8361 (DIPDual in-line packageIn microelectronics, a dual in-line package is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board or inserted in a socket.A DIP is usually referred to as a DIPn, where n is...
) - Amiga 1000Amiga 1000The A1000, or Commodore Amiga 1000, was Commodore's initial Amiga personal computer, introduced on July 23, 1985 at the Lincoln Center in New York City....
(NTSC); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model A (NTSC) - 8367 (DIP) - Amiga 1000Amiga 1000The A1000, or Commodore Amiga 1000, was Commodore's initial Amiga personal computer, introduced on July 23, 1985 at the Lincoln Center in New York City....
(PAL); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model A (PAL) - 8370 (PLCCPlastic leaded chip carrierA plastic leaded chip carrier is a chip carrier with a equiangular plastic housing. It is a reduced cost evolution of the ceramic leadless chip carrier ....
) - Amiga 500Amiga 500The Amiga 500 - also known as the A500 - was the first “low-end” Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987 - at the same time as the high-end Amiga 2000 - and competed directly against the Atari 520ST...
to Rev 5.x (NTSC); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model B to Rev 4.5 (NTSC) - 8371 (PLCCPLCCPLCC may refer to:* Plastic leaded chip carrier* Power line carrier communication...
) - Amiga 500Amiga 500The Amiga 500 - also known as the A500 - was the first “low-end” Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987 - at the same time as the high-end Amiga 2000 - and competed directly against the Atari 520ST...
to Rev 5.x (PAL); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model B to Rev 4.5 (PAL)
- 8361 (DIP
- ECS Agnus which can address up to 1 MB of Chip RAMChip RAMChip RAM is a commonly used term for the integrated RAM used in Commodore's line of Amiga computers. Chip RAM is shared between the central processing unit and the Amiga's dedicated chipset...
- 8372 - no data
* - 8372A - Amiga 500Amiga 500The Amiga 500 - also known as the A500 - was the first “low-end” Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987 - at the same time as the high-end Amiga 2000 - and competed directly against the Atari 520ST...
from Rev 6 (NTSC/PAL); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model B from Rev 6.0 to Rev 6.3 (NTSC/PAL); Commodore CDTV - 8375 (318069-16 only) (PAL) - Amiga 500Amiga 500The Amiga 500 - also known as the A500 - was the first “low-end” Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987 - at the same time as the high-end Amiga 2000 - and competed directly against the Atari 520ST...
from Rev 6 (PAL); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model B from Rev 6.4 (PAL) - 8375 (318069-17 only) (NTSC) - Amiga 500Amiga 500The Amiga 500 - also known as the A500 - was the first “low-end” Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987 - at the same time as the high-end Amiga 2000 - and competed directly against the Atari 520ST...
from Rev 6 (NTSC); Amiga 2000Amiga 2000The Amiga 2000, or A2000, is a personal computer released by Commodore in 1986. It is the successor to the Amiga 1000.-Features:Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000...
model B from Rev 6.4 (NTSC)
- 8372 - no data
- ECS Agnus which can address up to 2 MB of Chip RAMChip RAMChip RAM is a commonly used term for the integrated RAM used in Commodore's line of Amiga computers. Chip RAM is shared between the central processing unit and the Amiga's dedicated chipset...
- 8372AB - Amiga 3000Amiga 3000The Commodore Amiga 3000, or A3000, was the third major release in the Amiga computer family. Released in June 1990, it features improved processing speed, improved rendering of graphics, and a new revision of the operating system...
from Rev 6.1 to Rev 8.9 (NTSC/PAL) - 8372B - Amiga 3000Amiga 3000The Commodore Amiga 3000, or A3000, was the third major release in the Amiga computer family. Released in June 1990, it features improved processing speed, improved rendering of graphics, and a new revision of the operating system...
Rev 9 (NTSC/PAL) - 8375 (PAL) - Amiga 500 PlusAmiga 500+The Commodore Amiga 500 Plus is an enhanced version of the original Amiga 500 computer. It was notable for introducing new versions of Kickstart and Workbench, and for some minor improvements in the custom chips, known as the Enhanced Chip Set .- Introduction :The A500+ was released in several...
; Amiga 600Amiga 600The Amiga 600, also known as the A600 , is a home computer that was introduced at the CeBIT show in March 1992. The A600 was Commodore International's final model based on the Motorola 68000 CPU and the ECS chipset. It is essentially a redesign of the Amiga 500 Plus, with the option of an internal...
(PAL) - 8375 (NTSC) - Amiga 600Amiga 600The Amiga 600, also known as the A600 , is a home computer that was introduced at the CeBIT show in March 1992. The A600 was Commodore International's final model based on the Motorola 68000 CPU and the ECS chipset. It is essentially a redesign of the Amiga 500 Plus, with the option of an internal...
(NTSC)
- 8372AB - Amiga 3000
Chips by package
- 48-lead DIPDual in-line packageIn microelectronics, a dual in-line package is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board or inserted in a socket.A DIP is usually referred to as a DIPn, where n is...
Agnus (aka thin Agnus): 8361; 8367
- 84-contact PLCCPlastic leaded chip carrierA plastic leaded chip carrier is a chip carrier with a equiangular plastic housing. It is a reduced cost evolution of the ceramic leadless chip carrier ....
Fat Agnus (named Fat Lady on most Amiga2000 mainboard) 8370; 8371; 3872; 8372A; 8372AB; 8372B; 8375
Notes
Fat Agnus 1MB and Fat Agnus 2MB usually known as Super Agnus; Super Fat Agnus; Fatter Agnus; Big Agnus; Big Fat Agnus; Super Fat Agnus, but these aren't official names.
DMA Channels
| Priority | Name | Count | Cycles/Rasterline | Chip | Notes |
|---|---|---|---|---|---|
| MPU | 1 | varying | CPU | ||
| A | Blitter | 4 | varying | Agnus (internal) | yields 1/4 cycles to CPU when BLTPRI not active |
| B | Bitplane | 6 | 80 | Denise | impairs sprite channels on severe overscan Overscan Overscan is extra image area around the four edges of a video image that may not be seen reliably by the viewer. It exists because television sets in the 1930s through 1970s were highly variable in how the video image was framed within the cathode ray tube .-Origins of overscan:Early televisions... |
| C | Copper | 1 | varying | Agnus (internal) | |
| D | Audio | 4 | 4 | Paula | |
| E | Sprites Sprite (computer graphics) In computer graphics, a sprite is a two-dimensional image or animation that is integrated into a larger scene... |
8 | 16 | Denise | |
| F | Disk | 1 | 3 | Paula | |
| G | Memory Refresh | 1 | 4 | - | |
| Reference: Amiga 500 plus Service Manual | |||||
PLCC Versions
When swapping/upgrading chips pinouts need to be taken care of. Types are just mentioned for reference, four-digit types and pinouts/usage are not consistent.| OCS/ECS | ECS | ECS | AGA (Alice) | |
|---|---|---|---|---|
| A500/2000 | A3000 | A500+/600 | A4000/1200 | |
| 8370/1 | 8372 | 8375 | 8374 | |
| 1 | RD13 | DRD13 | DRD13 | DRD13 |
| 2 | RD12 | DRD12 | DRD12 | DRD12 |
| 3 | RD11 | DRD11 | DRD11 | DRD11 |
| 4 | RD10 | DRD10 | DRD10 | DRD10 |
| 5 | RD9 | DRD9 | DRD9 | DRD9 |
| 6 | RD8 | DRD8 | DRD8 | DRD8 |
| 7 | RD7 | DRD7 | DRD7 | DRD7 |
| 8 | RD6 | DRD6 | DRD6 | DRD6 |
| 9 | RD5 | DRD5 | DRD5 | DRD5 |
| 10 | RD4 | DRD4 | DRD4 | DRD4 |
| 11 | RD3 | DRD3 | DRD3 | DRD3 |
| 12 | RD2 | DRD2 | DRD2 | DRD2 |
| 13 | RD1 | DRD1 | DRD1 | DRD1 |
| 14 | RD0 | DRD0 | DRD0 | DRD0 |
| 15 | Vcc | Vcc | Vcc | Vcc1 |
| 16 | RST* | _RESET | _RESET | /RESET |
| 17 | INT3 | _INTR | _INTR | /INTR |
| 18 | DMAL | DMAL | DMAL | DMAL |
| 19 | BLS* | _BLISS | _BLISS | /BLS |
| 20 | DBR* | _BLIT | _BLIT | /DBR |
| 21 | RRW | _WE | _WE | /WE |
| 22 | PRW | R/W | R/W | R/W |
| 23 | RGEN* | _REGEN | _REGEN | _REGEN |
| 24 | AS* | _AS | _AS | NC2 |
| 25 | RAMEN* | _RAMEN | _RAMEN | /RAMEN |
| 26 | RGA8 | RGA8 | RGA8 | RGA8 |
| 27 | RGA7 | RGA7 | RGA7 | RGA7 |
| 28 | RGA6 | RGA6 | RGA6 | RGA6 |
| 29 | RGA5 | RGA5 | RGA5 | RGA5 |
| 30 | RGA4 | RGA4 | RGA4 | RGA4 |
| 31 | RGA3 | RGA3 | RGA3 | RGA3 |
| 32 | RGA2 | RGA2 | RGA2 | RGA2 |
| 33 | RGA1 | RGA1 | RGA1 | RGA1 |
| 34 | 28 MHz | 28 MHz | 28 MHz | SCLK |
| 35 | XCLK | A20 | A20 | A20 |
| 36 | XCLKEN* | _XCLKEN | _CDAC | 14 MHz |
| 37 | CDAC* | _CDAC | 7 MHz | /CDAC |
| 38 | 7 MHz | 7 MHz | CCKQ | 7 MHz |
| 39 | CCKQ | CCKQ | CCK | CCKQ |
| 40 | CCK | CCK | 14M | CCK |
| 41 | TEST | TEST | GND | /NTSC |
| 42 | Vss | Vss1 | DRA0 | GND2 |
| 43 | MA0 | DRA0 | DRA1 | DRA0 |
| 44 | MA1 | DRA1 | DRA2 | DRA1 |
| 45 | MA2 | DRA2 | DRA3 | DRA2 |
| 46 | MA3 | DRA3 | DRA4 | DRA3 |
| 47 | MA4 | DRA4 | DRA5 | DRA4 |
| 48 | MA5 | DRA5 | DRA6 | DRA5 |
| 49 | MA6 | DRA6 | DRA7 | DRA6 |
| 50 | MA7 | DRA7 | DRA8 | DRA7 |
| 51 | MA8 | DRA8 | _LDS | DRA8 |
| 52 | LDS* | _LDS | _UDS | Vcc2 |
| 53 | UDS* | _UDS | _CASL | NC1 |
| 54 | CASL* | _CASL | _CASU | /CAS |
| 55 | CASU* | _CASU | DRA9 | Vbb |
| 56 | RAS1* | DRA9 | _RAS1 | DRA9 |
| 57 | RAS0* | _RAS | _RAS0 | /RAS |
| 58 | Vss | Vss2 | GND | GND3 |
| 59 | A19 | A19 | A19 | A19 |
| 60 | A1 | A1 | A1 | A1 |
| 61 | A2 | A2 | A2 | A2 |
| 62 | A3 | A3 | A3 | A3 |
| 63 | A4 | A4 | A4 | A4 |
| 64 | A5 | A5 | A5 | A5 |
| 65 | A6 | A6 | A6 | A6 |
| 66 | A7 | A7 | A7 | A7 |
| 67 | A8 | A8 | A8 | A8 |
| 68 | A9 | A9 | A9 | A9 |
| 69 | A10 | A10 | A10 | A10 |
| 70 | A11 | A11 | A11 | A11 |
| 71 | A12 | A12 | A12 | A12 |
| 72 | A13 | A13 | A13 | A13 |
| 73 | A14 | A14 | A14 | A14 |
| 74 | A15 | A15 | A15 | A15 |
| 75 | A16 | A16 | A16 | A16 |
| 76 | A17 | A17 | A17 | A17 |
| 77 | A18 | A18 | A18 | A18 |
| 78 | LP* | _LPEN | _LPEN | /LPEN |
| 79 | VSY* | _VSYNC | _VSYNC | /VSYNC |
| 80 | CSY* | _CSYNC | _CSYNC | /CSYNC |
| 81 | HSY* | _HSYNC | _HSYNC | /HSYNC |
| 82 | Vss | Vss3 | GND | GND1 |
| 83 | RD15 | DRD15 | DRD15 | DRD15 |
| 84 | RD14 | DRD14 | DRD14 | DRD14 |
References: A500 Service Training, A3000 Service Manual, A500+ Service Manual, A1200 schematics