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6 Slot Backplane

A backplane which supports up to six expansion cards, meant to go into a 3U VME crate.



  • Direction-controlled buffers for address and data bus
  • Mixer for audio from CPU board and expansion slots
  • Detection of installed peripheral cards via detect lines
  • An I2C bus switch to allow CPU board independent access to each slot’s sideband bus
  • Extremely low jitter clock distribution

It’s intended to be used in conjunction with the backplane management card for power, but the required +5V and +12V rails can also be provided through a 3.81mm pitch pluggable terminal block instead.

Assembly Notes

Here are some notes about hardware revisions.

Rev 1

  • The ID EEPROM is an AT24CS16, which has a different protocol than the AT24CS32 specified in the schematic. The address pins are also "NC" there
  • Drop resistors for orange/yellow LEDs (R401, R107, R108) should be a lower value
    • R401 probably got assembled wrong
  • Drop resistors for yellow LEDs (R101, R102) should be slightly higher
    • Or, we just spec shittier green LEDs
    • They're just slightly too bright