Not having much else to do today, I measured the current draw of most of my calculators. I used a standard multimeter between the calculator and a 5V power supply (actually producing 5.1V), measuring current. After collecting and tabulating the data, I converted everything to microamps and shoved it through some basic math to give a measure of the average current draw (90% off, 9.5% idle, 0.5% busy).
Data!
The earliest TI-81s, as expected, used the most power when idle. However, when they were off, the multimeter's most sensitive setting couldn't accurately detect any current draw (which bottoms out at 0.1 μA). Of the z80 calculators I tested, the early TI-82 used the most power when off, and the early TI-81s the least. The TI-89 Titanium used the most power when off, even surpassing the CBL2. Calculators based off of the TI-82 (TI-81 ROM V2.0x, TI-82, TI-83 series) had significantly elevated power consumption when off compared to TI-81 derivatives, but generally used less power when operating. The TI-84 Plus tested uses 3.3V logic, which is significantly more efficient when operating; current draw when off is still high, but the TI-84 Plus runs more things in the background (like a clock).
The TI-82 and later TI-81s use a Toshiba TC14L010AF ASIC and a discrete Z80 IC (either a Zilog Z84C00 or a Toshiba T84C00). The TI-83 uses a similar construction, but integrates the Z80 into the ASIC. The TI-81 derivatives do the same, integrating a Z80 core into their T6A49/A (early TI-81) or T6A43 (later ROM 1.x TI-81, TI-85) ASICs. The TI-81 ROM 1.x and TI-85 use two column drivers and one row driver, whereas the TI-82 and its derivatives combine the row and column drivers into one small IC. The TI-86 uses one row driver and one column driver.
Data!
The earliest TI-81s, as expected, used the most power when idle. However, when they were off, the multimeter's most sensitive setting couldn't accurately detect any current draw (which bottoms out at 0.1 μA). Of the z80 calculators I tested, the early TI-82 used the most power when off, and the early TI-81s the least. The TI-89 Titanium used the most power when off, even surpassing the CBL2. Calculators based off of the TI-82 (TI-81 ROM V2.0x, TI-82, TI-83 series) had significantly elevated power consumption when off compared to TI-81 derivatives, but generally used less power when operating. The TI-84 Plus tested uses 3.3V logic, which is significantly more efficient when operating; current draw when off is still high, but the TI-84 Plus runs more things in the background (like a clock).
The TI-82 and later TI-81s use a Toshiba TC14L010AF ASIC and a discrete Z80 IC (either a Zilog Z84C00 or a Toshiba T84C00). The TI-83 uses a similar construction, but integrates the Z80 into the ASIC. The TI-81 derivatives do the same, integrating a Z80 core into their T6A49/A (early TI-81) or T6A43 (later ROM 1.x TI-81, TI-85) ASICs. The TI-81 ROM 1.x and TI-85 use two column drivers and one row driver, whereas the TI-82 and its derivatives combine the row and column drivers into one small IC. The TI-86 uses one row driver and one column driver.
