Sega Dreamcast Visual Memory
Last changed: 2003-07-22

How much power the VM uses in different clock modes

I have measured the power consumption of the VM in all clock modes I know. To do this I connected a simple DMM in current mode between a 6V power source and the battery compartment. I did this once with my SerialToVM connected and once stand-alone. The normal modes I tested were watch mode, sleeping while in watch mode and transferring data to the VM. In game mode I used a simple endless loop which used getkeys from tetris.s:

loop
	call getkeys
	jmp loop

To measure the power in sleep mode with different clock modes I sent the VM into sleep by pressing the sleep button while running the loop above.

The values for sub-clock mode were measured with RC clock oscillator still running (bit 1 of OCR = 0).

Before December 15th, 2000 the "Sleep SerialToVM" and "Stand-alone" columns were accidently swapped, sorry. The text version posted on vmu-dev on April 25th, 2000 was correct.

Mode SerialToVM Sleep SerialToVM Stand-alone Sleep stand-alone
6MHz9.2mA 3.7mA 8.6mA 3.0mA
3MHz6.0mA 2.4mA 5.4mA 1.65mA
600Khz3.6mA 1.3mA 2.9mA 0.55mA
300Khz3.2mA 1.1mA 2.4mA 0.35mA
32.8kHz1.5mA 0.9mA 0.65mA 0.15mA
16.4kHz1.4mA 0.9mA 0.65mA 0.15mA
watch1.0mA 0.25mA 0.85mA 0.1mA
Data transfer5mA, 8mA peak