RC208-68000 BOOTROM RAM 2
About the RC208-68000 BOOTROM RAM 2 PCB
RC208-68000 BOOTROM RAM 2 is an open source PCB design by MarkD833, published on GitHub under the CC-BY-NC-4.0 license. It is a 4-layer board measuring 101.6 × 53.3 mm, with 20 components from 10 distinct parts.
Other key parts include the 74LS125, 74LS139, SST39SF040, 74LS138 and AS6C4008-55PCN. By type, the board carries 9 ICs, 9 capacitors and 2 connectors.
It belongs with the retro computing designs in this gallery.
From the project
My Motorola 68000 & 68302 processors (+ SIO, PIO & MFP boards) for the RCBus ecosystem.
The old v1.0 board with the flash chips removed.
This board is an enhanced version of my earlier RC107 board. This board presents the flash memory at address 0x000000 at reset and disables access to the RAM. After 4 address strobes, the flash memory is automatically moved up to address 0x700000 and the RAM becomes available at address 0x000000.
After reset, the 74LS165 sets its Q7 output to a '1'. This '1' is then OR'd with address lines A20, A21 and A22 using 3 OR gates of the 74LS32 forcing their outputs to be a '1'. The outputs of the 3 OR gates are then fed into the A0, A1 and A2 inputs…
Main components on the RC208-68000 BOOTROM RAM 2
RC208-68000 BOOTROM RAM 2 bill of materials (BOM)
20 components, 10 distinct parts — part numbers from the project's BOM.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | 74LS125 | DIP-14_W7.62mm | U1 |
| 1 | 74LS139 | DIP-16_W7.62mm | U2 |
| 2 | SST39SF040 | DIP-32_W15.24mm | U3, U4 |
| 1 | 74LS138 | DIP-16_W7.62mm | U5 |
| 2 | AS6C4008-55PCN | DIP-32_W15.24mm | U6, U7 |
| 1 | 74LS165 | DIP-16_W7.62mm | U8 |
| 1 | 74LS32 | DIP-14_W7.62mm | U9 |
| 1 | RCBUS_80PIN_68000 RCBus_80PIN_68000 | RCBus_80p_Medium | J1 |
| 1 | CONN_02X03_ODD_EVEN Conn_02x03_Odd_Even | PinHeader_2x03_P2.54mm_Vertical | J2 |
| 9 | 100N 100n | C_Disc_D5.0mm_W2.5mm_P2.50mm | C1, C2, C3, C4, C5, C6, C7, C8 +1 |
RC208-68000 BOOTROM RAM 2 design files
The KiCad project lives in the MarkD833/RCBUS-68xxx repository on GitHub; these links point at the commit this page was built from.
RC208-68000 BOOTROM RAM 2: common questions
How big is the RC208-68000 BOOTROM RAM 2 PCB?
The RC208-68000 BOOTROM RAM 2 measures 101.6 × 53.3 mm, has 4 copper layers and is 1.6 mm thick.
How many components are on the RC208-68000 BOOTROM RAM 2?
20 components, from 10 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.
Where can I download the RC208-68000 BOOTROM RAM 2 design files?
From the MarkD833/RCBUS-68xxx repository on GitHub, which has the KiCad layout, the schematic and the BOM; the links under Design files point to each one.
Can I use the RC208-68000 BOOTROM RAM 2 design in my own project?
It is published under CC-BY-NC-4.0, which limits how it may be reused; read the license before building on it.
More boards in RCBUS-68xxx
RC200-Dev Backplane
188 × 102.9 mm90 parts2LCC-BY-NC-4.08
RC202-68000 SIO 1
101.6 × 53.3 mm40 parts4LCC-BY-NC-4.08
RC201-68000 CPU 2
101.6 × 53.3 mm37 parts4LCC-BY-NC-4.08
68302 CPU Board
101.6 × 53.3 mm37 parts4LCC-BY-NC-4.08
68000 LBE Board
101.6 × 53.3 mm34 parts4LCC-BY-NC-4.08
68000 SIO BOARD
101.6 × 53.3 mm33 parts4LCC-BY-NC-4.08
68000 CPU Board
101.6 × 53.3 mm32 parts4LCC-BY-NC-4.08
RC107-68000 ROM RAM 1
101.6 × 53.3 mm28 parts4LCC-BY-NC-4.08
68000 MPF BOARD
101.6 × 53.3 mm27 parts4LCC-BY-NC-4.08
RC203-68000 PIO 1
101.6 × 53.3 mm24 parts4LCC-BY-NC-4.08
68000 PIO BOARD
101.6 × 53.3 mm23 parts4LCC-BY-NC-4.08
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