The 1616 hardware

The Motherboard

• 7.5 MHz 68000. Later on I fiddled the timing PAL so the system ran at 15 MHz with a 16 MHz Thompson CPU.
• 512k dynamic RAM.
• Video timing via a 6845 CRT controller.  Main memory was used for the video buffer, with access arbitrated by the timing PAL.  The video refresh kept the dynamic RAMs pumped up.
• Bitmapped graphics!  Omitting the usual character generator ROM was a radical step, permitted only by the awesome processing power of the 68000.  Graphics resolutions were 320x200, 16 colours or 640x200, 4 of 16 colours. Later on a new video PAL and a bit of soldering permitted 960x512 monochrome for MGR.
• Programmable start address for the video RAM.  Allowed animation via page flipping.  The virtual console driver used this.
• Dual serial I/O (Z8530).
• Audio/analogue output via an 8-bit DAC.  Demultiplexed via an analogue switch and some op-amps to provide surround sound stereo!
• Audio/analogue input provided by the poor old DAC, a comparator and a software analogue-to-digital converter.
• Four eighty pin expansion slots.
• A Rockwell 6522 Versatile Interface Adaptor gave parallel I/O and timers.  This thing sweated blood.
• A Centronics printer port.
• A PC/XT keyboard interface.
• 64 kbytes of EPROM.
• Oops.  Make that 128k.
• Oops.  Make that 256k.

The disk controller card

• A 6MHz Z80
• 32k ROM
• 64k Static RAM
• WD1772 floppy disk controller
• Another Z8530 for two more serial ports which never got used
• An NCR5380 SCSI controller

The memory card

• Up to 4Mbytes of dynamic RAM.  Refresh was performed by a little eight-bit upcounter, some address multiplexors and some more PAL wizardry.
• An optional MMU was implemented via fast static RAM, the address multiplexors and more little PALs. It was never used.
• Another NCR5380 for much faster SCSI I/O

The graphics card

This was based on the TMS34010 CISC CPU with inbuilt graphics controller.  A really wierd chip.  I designed this card for a 68k system I'd developed at Keno Computer Systems.  That system happened to have the 1616 bus.  It also ran 1616/OS.

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Andrew Morton, 8 March 1999