The Sinclair ZX-81 16k RAM expansion pack was used to expand the memory of a basic 1k Sinclair ZX-81 or a 2k Timex-Sinclair 1000. It plugged into the rear expansion port of the machine. A number of commercial programs required that this RAM expansion pack be in place due to the small amount of memory in an unexpanded machine. The pack is not well supported when mounted to the machine and it should be removed before moving the computer, as it is very easy to crack the connector housing on the pack itself by applying too much pressure to it. I inadvertently did this to the one on my Timex-Sinclair shortly after buying it in 1982. Also, if the computer and/ or RAM pack are inadvertently jiggled while the system is on, you will likely lose any unsaved data.

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