Microbee Add-on boards
Additional functionality could be added to some Microbee models though optional add-on boards.
Standard Colour option
This is a colour board option for Standard model Microbees with a 3.375MHz CPU clock. It provides 32 foreground colours determined by IC 7 (a PROM) on the colour board and up to 64 different background colours although only 8 different combinations of background colours are possible at any one time.
Viatel upgrade option
This board option allowed the use of Viatel software (followed by Videotext later) to provide the 40 character wide screen mode.
Real Time Clock option
This board option allowed Standard and early Premium models to have a Real Time Clock (RTC).
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50 Way Expansion Kit
This is an add-on board designed for Standard models. It provides a 50 way Expansion Interface for connecting external peripherals and also provides video de-glitch functionality. The two functions are not related to each other and may be independently and optionally implemented during installation. The 50 way interface is identical to that normally provided by Static RAM (SRAM) Core boards and may be used to provide a second interface for those machines. The board is particularly useful for adding expansion capability to models that are fitted with Dynamic RAM (DRAM) Core boards since these do not incorporate a 50 way interface.
This board is installed beneath the Standard Main board and connects via an extended pin/socket arrangement as well as requiring a set of separate fly wires. See the 50 Way Expansion Kit Manual for construction and fitting details.