I found that sometimes by MBP enters a state where the discrete GPU draws 10W of power when the integrated CPU is selected - causing a nearly doubling of total power draw. More details, and ways to check below.
Of course I can't know if this is unique to me, caused by some software on my system, or is the cause of other peoples intermittent battery problems.
Background
I have a 15" MBP Touch, 2.9GHz, 16GB, Radeon Pro 460, 512GB. Got it a few days ago. I find that normally I can get ~6-9 hours of general dev work on a charge, which I consider pretty good. But I noticed that at one point my battery was draining faster than it should, even though I was on the Intel GPU, and nothing was doing much with the CPU. After some poking around, I noticed in iStat Menus that the discrete GPU was drawing 10W of power, which seemed odd, considering it was 'off'.
After some experimenting, I discovered that if the discrete was active, it's power draw would be around 4W (idle), but if the integrated was active, the discrete would draw 10W (which is on top of the power draw of the integrated GPU), and the total system power draw would be significantly higher.
Some values
Note that I also used a tool to directly probe the SMC sensor values, so this isn't an artifact of iStat Menus.
Some values from probing total system power (PSTR) and discrete GPU power (PS0R). Note that this was on AC power - the total system power values dropped by about 5W when on battery, but the differentials remained the same, meaning the problem nearly doubled power draw when on battery.
On discrete GPU:
PS0R: 4.27W (bytes b9 c9 88 40)
PSTR: 17.68W (bytes 0B d7)
On integrated GPU:
PS0R: 9.56W (bytes 43 f1 18 41)
PSTR: 24.22W (bytes 0c 1c)
After a reboot, the problem clears, and the discrete draws ~0.1W while idle, and the system total draw is around 9-11W.
While these particular values are obviously one time snapshots, I saw a similar result over time. When the problem exists, on the discrete, total power draw is a few W higher than it should be, but when on the integrated, the power draw is basically double what it should be.
Checking it out yourself
If you would like to monitor the values, I would recommend trying out iStat Menus (has a 14 day free trial). Turn on the sensors menu item. When you open that menu, you will see tons of values, but near the bottom you will find Radeon GPU Highside and System Total in the power section. You can hover over each item to see graphs of the values. You can also configure the menu item for the menu to report the values directly in the menubar - so next to my battery icon it displays the two power draws right next to each other.
The CPU menu item can also be configured to display which GPU is currently active.
I don't plan on keeping it that way in the long run (it eats a lot of menu bar space), but it is a good way to quickly see the state the system, and if the probable is showing up.
(And no, I am in NO WAY affiliated with iStat Menus. I own my own copy, and have used it for many years)
Is this really the problem?
No clue. Like I said, the problem clears after a reboot, and I get very good battery life, but since I found this problem yesterday, it has recurred twice. I also don't know if this is unique to the 460, unique to my particular machine, or something else.
The good thing about this is that it is probably a driver issue that could be fixed.
I captured a bunch of system dumps and reports and sent them to Apple in a Radar issue. I'm sure they will close it as a duplicate, or not an issue, or whatever, but I hope that the data makes it to someone who might be able to use it.
I'm hoping some others will be able to monitor the problem and see if this is a relatively wide spread problem, and the more noise it gets (if it deserves it), the more likely Apple will notice and look into it (even though they of course won't acknowledge it).
Of course I can't know if this is unique to me, caused by some software on my system, or is the cause of other peoples intermittent battery problems.
Background
I have a 15" MBP Touch, 2.9GHz, 16GB, Radeon Pro 460, 512GB. Got it a few days ago. I find that normally I can get ~6-9 hours of general dev work on a charge, which I consider pretty good. But I noticed that at one point my battery was draining faster than it should, even though I was on the Intel GPU, and nothing was doing much with the CPU. After some poking around, I noticed in iStat Menus that the discrete GPU was drawing 10W of power, which seemed odd, considering it was 'off'.
After some experimenting, I discovered that if the discrete was active, it's power draw would be around 4W (idle), but if the integrated was active, the discrete would draw 10W (which is on top of the power draw of the integrated GPU), and the total system power draw would be significantly higher.
Some values
Note that I also used a tool to directly probe the SMC sensor values, so this isn't an artifact of iStat Menus.
Some values from probing total system power (PSTR) and discrete GPU power (PS0R). Note that this was on AC power - the total system power values dropped by about 5W when on battery, but the differentials remained the same, meaning the problem nearly doubled power draw when on battery.
On discrete GPU:
PS0R: 4.27W (bytes b9 c9 88 40)
PSTR: 17.68W (bytes 0B d7)
On integrated GPU:
PS0R: 9.56W (bytes 43 f1 18 41)
PSTR: 24.22W (bytes 0c 1c)
After a reboot, the problem clears, and the discrete draws ~0.1W while idle, and the system total draw is around 9-11W.
While these particular values are obviously one time snapshots, I saw a similar result over time. When the problem exists, on the discrete, total power draw is a few W higher than it should be, but when on the integrated, the power draw is basically double what it should be.
Checking it out yourself
If you would like to monitor the values, I would recommend trying out iStat Menus (has a 14 day free trial). Turn on the sensors menu item. When you open that menu, you will see tons of values, but near the bottom you will find Radeon GPU Highside and System Total in the power section. You can hover over each item to see graphs of the values. You can also configure the menu item for the menu to report the values directly in the menubar - so next to my battery icon it displays the two power draws right next to each other.
The CPU menu item can also be configured to display which GPU is currently active.
I don't plan on keeping it that way in the long run (it eats a lot of menu bar space), but it is a good way to quickly see the state the system, and if the probable is showing up.
(And no, I am in NO WAY affiliated with iStat Menus. I own my own copy, and have used it for many years)
Is this really the problem?
No clue. Like I said, the problem clears after a reboot, and I get very good battery life, but since I found this problem yesterday, it has recurred twice. I also don't know if this is unique to the 460, unique to my particular machine, or something else.
The good thing about this is that it is probably a driver issue that could be fixed.
I captured a bunch of system dumps and reports and sent them to Apple in a Radar issue. I'm sure they will close it as a duplicate, or not an issue, or whatever, but I hope that the data makes it to someone who might be able to use it.
I'm hoping some others will be able to monitor the problem and see if this is a relatively wide spread problem, and the more noise it gets (if it deserves it), the more likely Apple will notice and look into it (even though they of course won't acknowledge it).
