Howto disable GPU manually to converse power?

[lilzz]

I have Pi unit running remotely by SSH into it. I do not need GPU therefore I like Pi to disable to converse power.

I have a custom voltage generator generates 5V to supply the Pi but voltage regulator is awfully hot as now.

I like to disable GPU and hopefully regulator gets less hot.

[DougieLawson]

It's not possible.

[rpdom]

I have Pi unit running remotely by SSH into it. I do not need GPU therefore I like Pi to disable to converse power.

I have a custom voltage generator generates 5V to supply the Pi but voltage regulator is awfully hot as now.

I like to disable GPU and hopefully regulator gets less hot.

As Dougie said, you can't disable the GPU.

The GPU runs the Pi hardware (not just the graphics). The ARM CPU only runs the OS.

If your voltage regulator is getting hot then it is not a very good voltage regulator. It is probably something like a 7805 linear voltage regulator which gets rid of the extra voltage as heat which is very wasteful. It would be better to get a cheap switching voltage regulator (or UBEC circuit) which wastes very little power as heat.

[jamesh]

The GPU will automatically go to lowest power state possible given the demands made on it. I don't think its possible to user specify the power features on the GPU.

[aTao]

It is probably something like a 7805 linear voltage regulator which gets rid of the extra voltage as heat which is very wasteful. It would be better to get a cheap switching voltage regulator (or UBEC circuit) which wastes very little power as heat.

You can get pin for pin replacements for the 78xx/79xx series that uses switchmode psu (buck converter) tech. http://www.ebay.co.uk/itm/like/27122675 ... 0&ff14=108

[lilzz]

No, I am not using a 78xx regulator I am using a 12VDC to 5VDC step down LM2576H-5V which is supposedly over 90% efficient, its switching regulator not a linear regulator and it gets hot.

I couldn't think of anything else besides getting the Pi consumes lower power.

[jdb]

What JamesH said is correct. The GPU will power off unused blocks once there is no requirement to use them.

In general, extensive clock gating is also used throughout the GPU design such that even if blocks are powered but largely unusued, a minimum (i.e. leakage) current is consumed.

The only real thing you can do to further reduce power consumption is switch off all the PLLs and drive everything from the crystal oscillator directly - bus, SDRAM, CPU, GPU etc. This obviously completely nobbles the performance of the chip.

[aTao]

Heres a page that has a link to a datasheet for that device http://www.datasheetcatalog.com/datashe ... 576H.shtml looks like you would expect 75% efficiency, should still be less than 2W at 1A, would that be hot?> dosent sound quite right to me. Maybe you could check what current the RPi is drawing.

[mahjongg]

the purposed efficiency is 77%, that means it uses 1 - 0,77 = 0.23 Watt for itself for each watt that it delivers to its output. In this case it has to deliver less than 5W to a PI (1Amp @5V) so it would use up less than 1,15 Watt.

1 Watt dissipation should be barely enough to get a TO-220 sized device like that lukewarm.

That means there is something badly wrong with your switcher! Probably the choice of the coil or diode may have something to do with it, or it got damaged somehow.

I would throw it away, and buy a cigar plug adapter. These cost almost nothing ($5 to $10) and are designed to convert 12V from a car battery to 5V @ 1A, they contain a switcher, as they are thumb sized, thus too small for a linear regulator that must dissipate 7 Watt to deliver 1A. They also have a correctly wired USB output connector, and are guaranteed to give 5V within 5% @ 1 Ampere.