2 layers64.2 × 28.5 mm
4 layers81.8 × 46.1 mm
Agnus
LinuxJedi/RAMesses11RAMesses Amiga 2MB Chip RAM board
- Size
- 81.8 × 46.1 mm
- Copper layers
- 4
- Thickness
- 1.62 mm
- Parts
- 22
- Nets
- 97
- Pads
- 271
- Tracks, vias
- 603, 75
- Pours
- 5
- Routed
- Yes
- KiCad
- KiCad 7 (file 20221018)
- Created
- 19 Feb 2023
- Updated
- 23 Sep 2025
Overview
Agnus is an open-source printed circuit board by LinuxJedi, from the LinuxJedi/RAMesses repository on GitHub, published under the GPL-2.0 licence. It is a 4-layer board of 81.8 × 46.1 mm with 22 parts on 97 nets, routed with 603 tracks and 75 vias.
It is built around the 74LVC2G157DCU and 74AHC1G08GW. Its parts include 10 capacitors, 7 ICs, 2 resistors and 2 connectors. It belongs with the retro computing and games boards of this library.
Main components
2
74LVC2G157DCU
VSSOP-8-0.5mm-40℃~+85℃ 1.65V~5.5V 10uA 32mA 32mA 4ns@5V,50pF 74LVC Power-off protection、Level shifting Single Supply VSSOP-8-0.5mm Signal Switches, Multiplexers, Decoders ROHSTexas InstrumentsSignal Switches, Multiplexers, Decoders
74AHC1G08GW
SOT-353-40℃~+125℃ 1 1.5V~3.85V 1.9V~2V、2.9V~3V、3.7V~3.94V、4.4V~4.5V 100mV、360mV~550mV 10nA 2 2V~5.5V 500mV~1.65V 74AHC Series 9.5ns@3.3V,15pF AND Gate Overvoltage-tolerant input StandardCMOS SOT-353 Logic Gates ROHSMDDLogic Gates
README
README.mdRAMesses
RAMesses is a plug and play Amiga 500/2000/CDTV board which will convert a 2MB 8375 Agnus to work in a 512KB/1MB motherboard and add 2MB of RAM. RAMesses has two switchable modes, the first gives the full 2MB to Chip RAM, the second gives 1MB of Chip RAM and 512KB of Pseudo-Fast RAM. This is for compatibility with older games.
The project is in two parts, one is a board that sits in the Agnus socket and the other is a board that sits in the Gary socket, the two boards need to be linked together with a four wire cable, preferably around 20cm in length.
BOM
Agnus
| Designator | Component |
|---|---|
| C1 - C9 | 100nF 0603 capacitor |
| C10 | 22pF 0603 capacitor |
| R1 | 150R 0603 resistor |
| R2 | 4.7K 0603 resistor |
| U4, U5, U7 | 74LVC2G157 VSSOP |
| U1 | Winslow W9328 PLCC Plug |
| U2 | PLCC-84 socket |
| U3 | 74AHC1G08 SOT-23 |
| U6 | GM71C18163C SOJ-42 |
| JP1, J6 | 01x02 2.54mm horizontal pin header |
Notes:
- The W9328 has been tested with the ZC158 variant, but all other height variants should would.
- For U6 you could also use K4F151611, K4E151611 and AS4C1M16E5. Potentially other RAM chips will work too.
- A previous version of this README had C10 as 22nF, it is supposed to say 22pF. Using 22nF would kill the clock signal (thanks to Moritz for reporting it)
Gary
This simply requires a 48pin DIP socket and 2 strips of 24pin machined pins.
Assembly
Hand soldering the PLCC plug is highly recommended, this seems to create a stronger bond and this will be the most physically stressed part.
The two boards should be linked using four wires of roughly 26-32AWG. The order of the four wires is the opposite on each board (1 - 4 on one board, 4 - 1 on the other).
Usage
You need an 2MB 8375 Agnus in the PLCC socket. Known models to work are:
- 318069-18 PAL
- 318069-10 PAL
- 390544-01 PAL
- 318069-11 NTSC
- 390544-02 NTSC
Please note that there are 1MB versions of the 8375 that are not compatible. The 2MB A3000 Agnus chips are not compatible.
Put a jumper on the bottom VBB jumper pins if the Agnus chip is marked as VBB.
The jumper on the top RAM Mode will give 2MB of chip RAM, the jumper removed will provide 1MB of chip RAM and 0.5MB of Pseudo-Fast RAM.
Sponsorship
If you like this design and use it, please consider donating so I can design more Amiga things:
- Ko-fi: https://ko-fi.com/linuxjedi
- PayPal: https://paypal.me/linuxjedi
Parts
22| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | 0.1uF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C1, C2, C3, C4, C5, C6, C7, C8, C9 |
| 3 | 74LVC2G157 | Package_SO:VSSOP-8_2.3x2mm_P0.5mm | U4, U5, U7 |
| 1 | 150 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1 |
| 1 | 22pF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C10 |
| 1 | 4.7K | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R2 |
| 1 | 74AHC1G08 | Package_TO_SOT_SMD:SOT-23-5_HandSoldering | U3 |
| 1 | ADDR | Connector_PinSocket_1.27mm:PinSocket_1x04_P1.27mm_Vertical | J1 |
| 1 | Agnus8372 | A500:PLCC Plug | U1 |
| 1 | Agnus8375 | Package_LCC:PLCC-84_THT-Socket | U2 |
| 1 | Conn_01x02 | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Horizontal | J6 |
| 1 | GM71C18163C | A500:SOJ-42 | U6 |
| 1 | VBB | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Horizontal | JP1 |
Questions
How big is the Agnus PCB?
It measures 81.8 × 46.1 mm and has 4 copper layers, 1.62 mm thick.
What parts does the Agnus use?
22 parts, built around the 74LVC2G157DCU and 74AHC1G08GW. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Agnus KiCad files?
From the LinuxJedi/RAMesses repository on GitHub, at the commit this page was made from: the board is Agnus/Agnus.kicad_pcb and its schematic Agnus/Agnus.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Agnus design in my own project?
Its repository publishes it under the GPL-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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