I also lean toward the view that it is best to get a better power supply, but keeping an eye on power consumption is still a good idea.
I have a pi running from USB and booting from an old, slow 500 MB sd card. It is very stable and boots reliably. Previously, with an 8GB class 10 SD card, and a 4GB class 6 card, I had a bit of instability but frequent trouble booting. I tried several power supplies, all of which should have been satisfactory (including the one that was bundled with the Pi), which did not help. 1A doesn't give you a lot of headroom.
What did help?
- A gold standard, onboard power supply card (about $25), borrowed from my other Pi.
- Using a small, slow SD card.
Considering how little current a Pi is able to use, there seems to be very little attention given to the power consumption of SD cards and USB keys. There is quite a range. I checked several USB keys that reported requirements as low as 50 mA and as high as 300 mA. Respecting SD cards, Wikipedia says:
Quote:The power consumption of SD cards varies by its speed mode, manufacturer and model.
During transfer it may be in the range of 66–330 mW (20–100 mA at a supply voltage of 3.3 V). Specifications from TwinMos technologies list a maximum of 149 mW (45 mA) during transfer. Toshiba lists 264–330 mW (80–100 mA).[72] Standby current is much lower, less than 0.2 mA for one 2006 Micro SD card... Modern UHS-II cards can consume up to 2,88W, if the host device support bus speed mode SDR104 or UHS-II.
CONCLUSIONS
If the standby current of the SD is in the range of 0.2 mA, it seems unlikely that pulling it out would have any impact. Of course, the characteristics of MediaPi's card may be different.
1A doesn't give you a lot of headroom to waste 300 mA on an USB key
If you are using a USB key,
- pay attention to its power consumption
- It makes sense to boot from a cheap, slow, small capacity (and low power) SD card.
