OpenEarlyMacsRAMexpansion
About the OpenEarlyMacsRAMexpansion PCB
OpenEarlyMacsRAMexpansion is an open source PCB design by Builder68, published on GitHub under the CERN-OHL-S-2.0 license. It is a 2-layer board measuring 137 × 92 mm, with 60 components from 18 distinct parts.
Other key parts include the 74HCT32, 74HCT253, 74AHCT139, 74HCT08D and AS4C1M16E5/F5_SOJ. By type, the board carries 25 resistors, 15 capacitors, 12 ICs, 4 connectors and 2 diodes.
From the project
4 MB RAM upgrade for Macintosh 128K / 512K / 512Ke computers
This upgrade utilizes 1Mb x 16-bit RAM ICs with 1024 refresh cycles, providing up to 4MB of RAM for Macintosh 128K and 512K equipped with the 128KB ROM (Macintosh Plus ROM). Testing has confirmed compatibility with a Macintosh 512Ke, including concurrent use with the ROM-INATOR board. Furthermore, installing this memory expansion alongside a SCSI card (like the MacSnap SCSI) enables the 128KB ROM to identify the machine as a Mac Plus.
Main components on the OpenEarlyMacsRAMexpansion
OpenEarlyMacsRAMexpansion bill of materials (BOM)
60 components, 18 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 74HCT32 | SO-14_3.9x8.65mm_P1.27mm | U1 |
| 3 | 74HCT253 | SO-16_3.9x9.9mm_P1.27mm | U2, U10, U11 |
| 1 | 74AHCT139 | SO-16_3.9x9.9mm_P1.27mm | U3 |
| 1 | 74HCT08D | SO-14_3.9x8.65mm_P1.27mm | U4 |
| 2 | AS4C1M16E5/F5_SOJ | SOJ-42_400mil | U5, U6 |
| 2 | 74HCT244 | SOIC-20W_7.5x12.8mm_P1.27mm | U7, U8 |
| 1 | 74HCT257 | SO-16_3.9x9.9mm_P1.27mm | U9 |
| 1 | (U12E) | DIP-20_W7.62mm_Socket | U12 |
| 1 | (U12E) | DIP-20_Socket_INV_Flip | J4 |
| 1 | (U13E) | DIP-20_Socket_INV_Flip | J5 |
| 2 | JST_06 | JST_PH_S6B-PH-K_1x06_P2.00mm_Horizontal | J11, J12 |
| 1 | SW_DIP_x06 | SW_DIP_SPSTx06_Slide_Omron_A6H-6101_W6.15mm_P1.27mm | SWB1 |
| 1 | SW_DIP_x08 | SW_DIP_SPSTx08_Slide_Omron_A6H-8101_W6.15mm_P1.27mm | SWB2 |
| 2 | SZMMSZ5V1T1G | D_SOD-123 | D1, D2 |
| 15 | 0.1 | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2, C3, C4, C5, C6, C7, C8, C9 +7 |
| 17 | 47 | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1, R4, R5, R6, R7, R9, R10, R11 +9 |
| 7 | 2.2K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R2, R3, R8, R16, R21, R24, R26 |
| 1 | 1K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R22 |
OpenEarlyMacsRAMexpansion design files
The KiCad project lives in the Builder68/OpenEarlyMacsRAMexpansion repository on GitHub; these links point at the commit this page was built from.
- LayoutEDA/RAMEXPB_V3.kicad_pcb
- SchematicEDA/RAMEXPB_V3.kicad_sch
OpenEarlyMacsRAMexpansion: common questions
How big is the OpenEarlyMacsRAMexpansion PCB?
The OpenEarlyMacsRAMexpansion measures 137 × 92 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the OpenEarlyMacsRAMexpansion?
60 components, from 18 distinct parts. The full bill of materials is listed on this page.
Where can I download the OpenEarlyMacsRAMexpansion design files?
From the Builder68/OpenEarlyMacsRAMexpansion repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.
Can I use the OpenEarlyMacsRAMexpansion design in my own project?
Yes, under the terms of its CERN-OHL-S-2.0 license, which Builder68 chose for the repository.