Re: Two new blog posts of interest to members of this forum Message #6 Posted by Eric Smith on 19 Sept 2011, 4:55 p.m., in response to message #4 by Steve Simpkin
The CPU used in the original Voyager calculators did NOT include any ROM, RAM, or LCD driver on-chip. There was a second chip, "R2D2", which contained the RAM, ROM, and Display Driver. The CPU was a minor variant of the one used in the 41C.
The HP-15C had more RAM and ROM than the other Voyager models, so it contained two R2D2 chips. The second R2D2 was in a smaller, lower pin-count package, with the display driver not bonded out.
It wasn't until many years later that they did a cost reduction, putting the CPU and R2D2 functions into one chip. The 15C still needed an additional R2D2.
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