OMEGA expander - CONCEPT


The Aquarius was shipped as a pared-down system to keep costs low and to promote future sales of expansion devices, including RAM, modems, etc. To counteract these deficiencies and to create a one-stop expansion device for Aquarius systems, an expander should be developed that includes the devices lacking in the original.


I took for granted the ability to acquire and use the Mini Expander when I got back in to Aquarius in late 2018, but I soon discovered that many of my peers in the UK and EU found it difficult and expensive to acquire the unit. It commonly comes with two Aquarius Control Pads, but even those are difficult to find outside the United States. If owning a Mini Expander were merely about adding joystick ports, that would be one thing, but the Mini Expander also increases the number and complexity of audio channels on the stock Aquarius, a feature that SHOULD have been included, but was not for cost-cutting reasons. Additionally, it allows the use of BOTH a RAM expansion cartridge and a program ROM cartridge at the same time... rarely an issue on the dozen or so ROM titles available for the Aquarius, but a nice feature nonetheless.

So after I reverse-engineered the PCB for the Aquarius motherboard, I decided to do the same for the Mini Expander.

Desired Features

  • Fast, bank-switched RAM

  • RTC (real-time clock)

  • Dual AY-3-8910 sound chips with up to FOUR controller inputs

  • USB ports for keyboards, mice, and modern joysticks

  • SD/USB removable storage, and a more flexible extension to the core system functions (KERNEL)

  • Have the same form-factor as the Mini Expander

Feature Discussion

    • Bank-Switched RAM

      • All banks use CYPRESS (Infineon) CY62158E (1M words x 8 bit) SRAM

      • Reserve IO $00E7: $00 - $39 for management routines (or ignore)

      • Paged 16k "LO RAM "expansion memory: $4000 - $7FFF

        • 16k @ 64 pages

        • Paged via IO $00E7: $40 - $7F

      • Paged 16k "MID RAM "expansion memory: $8000 - $BFFF

        • 16k @ 64 pages

        • Paged via IO $00E7: $80 - $BF

      • Paged 16k "HI RAM" expansion memory: $C000 - $FFFF

        • 16k @ 64 pages

        • Paged via IO $00E7: $C0 - $FF

      • Xilinx CPLD (44 pins of IO)

    • RTC

      • IO device with 8 bytes for CC YY MM DD HH MM SS hh

    • Dual AY-3-8910 Sound Chips

      • First chip maps to same range as Mini Expander

      • Second chip maps to offset range

    • USB port for Keyboard, Mice, and Modern Joysticks

      • Keyboard input from modern keyboards

      • Mouse device

      • Joystick devices

    • SD/USB storage