3 ms·
I remember overclocking my calculator (TI-85, 1992, Z80 CPU) ... its LO was a 2.7K/22pF RC oscillator which gave it an approximately 2.5MHz clock. To get this t
by gorkish 3y ago
I remember overclocking my calculator (TI-85, 1992, Z80 CPU) ... its LO was a 2.7K/22pF RC oscillator which gave it an approximately 2.5MHz clock. To get this type of oscillator to speed up you'd normally lower the capacitance a bit.
The reason that this story is interesting is that in most cases you could just yank C9 entirely and with nothing more than a resistor between the clock pins, you'd get a roughly 300% performance increase. I guess the parasitic capacitance was enough to still oscillate a bit although mostly it would have been random. Looking back, this was basically a CPU being clocked with 50mhz noise and still running happily! Amazing!
- lloydatkinson 3y agoNot quite the same but I once was bored enough to keep trying to see how low power a solar powered calculator could work with. I held my hand over the solar panel at various lengths until the screen cut out and while doing this I just kept hitting random keys and while lifting my hand up. One day when I did this I must have hit the one in a million chance. It started rapidly counting up by itself! I think I only got it to happen once more. I suspect the fluctuating voltage and it trying to do calculations while I was pressing keys was just enough to get some gates latched into the wrong state, somehow.
- gorkish 3y agoGlitching the power to force a CPU to misbehave at the right time is a time honored hacking technique! Great story
- bobim 3y agoGood memories... I ended up adding a switch under the cells cover because the mod was just draining these way faster. But curve plotting was finally snappy.