On 06/16/2016 11:00 AM, Lennart Sorensen wrote: > On Wed, Jun 15, 2016 at 06:15:30PM -0400, James Knott via talk wrote: >> > At work years ago, we had "no break power", where incoming AC ran a >> > motor connected to an alternator and an 8 ton flywheel. When the power >> > failed, a clutch would kick in the diesel, with the flywheel maintaining >> > the power, while starting the diesel. One problem though was the output >> > AC frequency was slightly low and threw off the real time clocks in the >> > computers. > Who built a computer that cared about AC frequency to drive the real > time clock? Never heard of anyone doing that.
Data General Nova & Eclipse computers had a choice of AC power or various clock rates derived from a crystal. The crystal wasn't all that accurate, but normally AC is. > Must have been a large machine given all microcomputers are fed DC from > their power supply and have no clue nor care what the AC frequency was. The Data General Nova predates microprocessors. It was first build around 1969, IIRC. The Eclipse, while a later generation, used the same basic I/O board, which included the RTC circuits, along with serial port for the console and ports for the paper tape punch & reader. Incidentally, one thing I did was modify those boards from 20 mA current loop to RS-232 for the console and also replaced the fixed crystal serial port clock (you had to change the crystal to change speeds) with a baud rate generator chip that used a colour burst crystal to generate a variety of baud rates. With the 2 mods, those boards moved from 110 b/s Teletypes, to 9600 b/s CRT terminals for the console. --- Talk Mailing List [email protected] https://gtalug.org/mailman/listinfo/talk
