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.