Dan Piponi @dpiponi@mathstodon.xyz
Public

"Sinclair in his quest for miniaturisation, to produce a true pocket calculator, wanted to use button cells rather than normal batteries, but these would be drained in minutes by the chip and the LED display. However, Chris Curry and Jim Westwood...found that the power to the chip did not have to be on continuously, it could be pulsed and the internal capacitance of the chip would store enough electrical charge to keep it working till the next power pulse. Power pulses lasting 1.7 microseconds are used, at a frequency of 200 KHz during calculations and 15KHz between each operation, reducing the power consumption to 25 to 30 mW. Texas Instruments did not recommend operating in this way, but it allows the Executive to get about 20 hours continuous operation from 3 small mercury button cells."

vintagecalculators.com/html/si

Dan Piponi @dpiponi@mathstodon.xyz
Public

I can't resist mentioning (again) one of my favourite bugs:

The Atari 2600 game Haunted House has an incorrect instruction which showed up in the emulator I wrote and yet the game works fine on most real consoles.

It turns out that if you accidentally use SBC 15 on a real console (subtract data in address 15) when you intended SBC #15 (subtract 15), and address 15 doesn't connect to anywhere so is just free floating, then the number 15 that was part of the instruction lingers like a decaying ghost in the capacitance of the data bus and gets read back as the missing data - if you're lucky to own a console with enough capacitance.

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