8870 Adventures

© Joe Farr, 2011 – 2026

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Category: Help

  • Cables

    It’s a sad fact that when an 8870 is removed the animals in charge usually just cut through all the cables. I’ve seen keyboard cables cut because they couldn’t figure out how to removed a SAS connector – it ain’t rocket science. Anyway, I’ll list here all the information I can find and figure-out on…

  • Communication interface personality boards

    There are many different ways to connect an 8870 to it’s VDUs, printers and the outside world in general. The 8870 supports PLC (Programmable Line Controller) devices that provide a lot of interface options and protocols but for general connectivity of VDUs and modems, the ALME (Asynchronous Line Multiplexer Extended) is the preferred and easiest…

  • 8251 Datasheet

    The 8251 is a Programmable Communication Interface controller and is found inside a DAP4 CPU board 1528-xx and form the interface between the CPU board electronics and the external personality interface board.

  • TC550 Memory Datasheet

    The TC550 is a 256 word by 4 bit memory and two of these memories are usually found inside a DAP4 CPU board 1528-xx. They are extremely low power CMOS memories and as such are used as NVR (None-Volatile RAM) by the CPU board to store user changeable configuration data.