Real-Time Clock

HP9825.COM

The Story of the Little Computer That Could!

 

HP 98035 Board 1

HP 98035 Board 2


These two cards are from the HP 98035A real-time clock card (code name Thyme). They were developed by a visiting engineer from HP’s Boeblingham Division. The real-time card is based on a low-power clock chip (large, unmarked, black rectangle on the left side of the lower board) originally developed for digital watches and uses an HP-designed Nanoprocessor (large grey chip with an HP logo on the right side of the lower board) to link the clock chip to the HP 9825A.

This is the same Nanoprocessor that Dick Barney used for developing the HP 98034A HPIB card and presumably some of Ed Schlotzhauer’s Nanoprocessor code for the HP 98034A was reused for the HP 98035A. Note that this Nanoprocessor is from a later batch than the one shown in the photos of the HP 98034A, which is obvious from the more professional markings on the chip. The ROM for the Nanoprocessor sits just to the right of the Nanoprocessor chip.

The large hole in the lower board once held a NiCd battery, which kept the clock chip powered up while the desktop calculator was switched off. However, after a quarter of a century, the battery had failed and was leaking electrolyte, so it was removed to prevent further deterioration of the board.

 


Information on the I/O pages of this site came from interviews with: Don Morris, Geoff Chance, Chris Christopher, Mike Kolesar, John Nairn, Dick Barney, Larry Smith, Ed Schlotzhauer, and from the memories of Steve Leibson.
 

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This site exists strictly for educational purposes. Nothing is for sale here. Substantial material from various issues
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All text Copyright 2004 to 2017 - Steve Leibson

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