MOS Technology Agnus

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MOS 8367R0 - Agnus Commodore Amiga 1000 - main board - MOS 8367R0-7824.jpg
MOS 8367R0 - Agnus

The MOS Technology "Agnus", usually called Agnus, is an integrated circuit in the custom chipset of the Amiga computer. The Agnus, Denise and Paula chips collectively formed the OCS and ECS chipsets.

Contents

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 transistors and contains DMA Channel Controllers. According to Jay Miner, original Agnus was fabricated in 5 μm manufacturing process like all OCS chipset. 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.

Chips by capability

Agnus chip (MOS Technology 8370 R3) CBM 8370R3 top metal.jpg
Agnus chip (MOS Technology 8370 R3)

* Somewhere 8372A Agnus mentioned as simply "8372".

Chips by package

Notes
Fat Agnus 1MB and Fat Agnus 2MB usually known as Super Agnus; Super Fat Agnus; Fatter Agnus; Big Agnus; Big Fat Agnus, but these aren't official names.

DMA Channels

PriorityNameCountCycles/RasterlineChipNotes
MPU1varyingCPU
ABlitter4varyingAgnus (internal)yields 1/4 cycles to CPU when BLTPRI not active
BBitplane680Deniseimpairs sprite channels on severe overscan
CCopper1varyingAgnus (internal)
DAudio44Paula
E Sprites 816Denise
FDisk13Paula
GMemory Refresh14-
Reference: Amiga 500 plus Service Manual

Pinout

PLCC Versions

When replacing or upgrading chips, pinouts need to be taken care of. Types are just mentioned for reference; four-digit types and pinouts/usage are not consistent. [1]

PinOCS/ECSECSAGA (Alice)Description
A500/2000A3000A500+/600A4000/1200
8370/1837283758374
1RD13DRD13DRD13DRD13Data Bus 16 bit, bit 13
2RD12DRD12DRD12DRD12.
.
.
3RD11DRD11DRD11DRD11
4RD10DRD10DRD10DRD10
5RD9DRD9DRD9DRD9
6RD8DRD8DRD8DRD8
7RD7DRD7DRD7DRD7
8RD6DRD6DRD6DRD6
9RD5DRD5DRD5DRD5
10RD4DRD4DRD4DRD4
11RD3DRD3DRD3DRD3
12RD2DRD2DRD2DRD2
13RD1DRD1DRD1DRD1
14RD0DRD0DRD0DRD0Data Bus 16 bit, bit 0
15VccVccVccVcc1+5V ±5%
16RST*_RESET_RESET/RESETGlobal RESETn, low active
17INT3_INTR_INTR/INTR
18DMALDMALDMALDMAL
19BLS*_BLISS_BLISS/BLS
20DBR*_BLIT_BLIT/DBR
21RRW_WE_WE/WE
22PRWR/WR/WR/W
23RGEN*_REGEN_REGEN_REGEN
24AS*_AS_ASNC2
25RAMEN*_RAMEN_RAMEN/RAMEN
26RGA8RGA8RGA8RGA8
27RGA7RGA7RGA7RGA7
28RGA6RGA6RGA6RGA6
29RGA5RGA5RGA5RGA5
30RGA4RGA4RGA4RGA4
31RGA3RGA3RGA3RGA3
32RGA2RGA2RGA2RGA2
33RGA1RGA1RGA1RGA1
3428 MHz28 MHz28 MHzSCLK
35XCLKA20A20A20
36XCLKEN*_XCLKEN_CDAC14 MHz
37CDAC*_CDAC7 MHz/CDAC
387 MHz7 MHzCCKQ7 MHz
39CCKQCCKQCCKCCKQ
40CCKCCK14MCCK
41TESTTESTGND/NTSC
42VssVss1DRA0GND2
43MA0DRA0DRA1DRA0Memory address bus 9 bit, bit 0 (except 8375 which is bit 1)
44MA1DRA1DRA2DRA1.
.
.
45MA2DRA2DRA3DRA2
46MA3DRA3DRA4DRA3
47MA4DRA4DRA5DRA4
48MA5DRA5DRA6DRA5
49MA6DRA6DRA7DRA6
50MA7DRA7DRA8DRA7
51MA8DRA8_LDSDRA8Memory address bus 9 bit, bit 8 (except 8375 which is bit _LDS)
52LDS*_LDS_UDSVcc2
53UDS*_UDS_CASLNC1
54CASL*_CASL_CASU/CAS
55CASU*_CASUDRA9Vbb
56RAS1*DRA9_RAS1DRA9
57RAS0*_RAS_RAS0/RAS
58VssVss2GNDGND3
59A19A19A19A19
60A1A1A1A1
61A2A2A2A2
62A3A3A3A3
63A4A4A4A4
64A5A5A5A5
65A6A6A6A6
66A7A7A7A7
67A8A8A8A8
68A9A9A9A9
69A10A10A10A10
70A11A11A11A11
71A12A12A12A12
72A13A13A13A13
73A14A14A14A14
74A15A15A15A15
75A16A16A16A16
76A17A17A17A17
77A18A18A18A18
78LP*_LPEN_LPEN/LPEN
79VSY*_VSYNC_VSYNC/VSYNC
80CSY*_CSYNC_CSYNC/CSYNC
81HSY*_HSYNC_HSYNC/HSYNC
82VssVss3GNDGND1Ground, common on whole board
83RD15DRD15DRD15DRD15Data Bus 16 bit, bit 15
84RD14DRD14DRD14DRD14Data Bus 16 bit, bit 14

References: A500 Service Training, A3000 Service Manual, A500+ Service Manual, A1200 schematics

See also

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References

Sources
Notes
  1. George Robbins (14 October 1992). "Difference of 8372A vs 8375". Newsgroup:  comp.sys.amiga.hardware. Usenet:   35861@cbmvax.commodore.com . Retrieved 1 October 2018.