Does sleep mode actually save battery?

[spooky69]

Pretty straightforward question here...does putting the Reader (mine is the 505) into sleep mode actually reduce the power drain on the battery versus just leaving it idle? I know that the OS is still running even while it's in sleep mode, which makes me wonder if it serves any function other than offering the pleasure of rocking that sliding power switch...while actually draining the battery a little more due to the extra page refreshes needed for the shut down and start-up. If it doesn't make any difference in the power consumption, I'd rather just have the screen be unchanged when I pick it up since I'm all into the idea of that cool e-ink technology. If this is pretty much exactly the same as putting into sleep mode (except for the fact that I would assume that sleep mode automatically shuts off that notoriously subtle audio-playing feature), then why even have that feature there in the first place? Is it for the peace of mind of people who don't like "active" displays? I put all these questions and more to the loyal MobileRead patrons, and I expect thorough and accurate answers immediately.

[HarryT]

No, the power consumption is pretty constant, whether the Reader is on or "off". I guess that people just aren't used to seeing displays with something on them still when they "turn off" a machine. All that the "off" switch really does on the Reader is to blank the screen and disable most of the buttons. Prevents accidental key presses while you're carrying the machine around, I guess.

[spooky69]

Okay, that pretty much answers my question, but let me also ask: does turning the display off with the power switch put it into the same state as sleep mode? I'd imagine it's the same, but one of you probably knows definitively. Also, this was probably addressed in the firmware update thread, but I saw something about a "complete off" option. Does that mean that we'll be able to set the reader to shut off by using the only power switch? I'd imagine it's either that or the "complete off" option would somehow be different from the current shut down function.

[JSWolf]

Unless you actually turn OFF the reader witht he menu item, it's in sleep mode when the screen is blank.

[Penforhire]

I've been curious about this. It is a tiny waste of energy to blank the screen when it sleeps (and restore the page again). Seems like it should have been just a key-lock mode where the screen is unchanged. Unless Sony figured people would be confused by the key-lock with no display indication? Somehow every Ipod user manages to deal with its key-lock switch.

Unless there IS power consumed to maintain the e-ink page, not what I was led to believe.

[KorrMuraan]

Originally Posted by Penforhire

Unless there IS power consumed to maintain the e-ink page, not what I was led to believe.

yeah seems like deceptive marketing

I was also led to believe that the reader only used power to change the page, but apparently the OS is running all the time

[spooky69]

P C P

[NatCh]

Originally Posted by spooky69

Okay, that pretty much answers my question, but let me also ask: does turning the display off with the power switch put it into the same state as sleep mode?

It's the same.

[NatCh]

Originally Posted by KorrMuraan

yeah seems like deceptive marketing

I was also led to believe that the reader only used power to change the page, but apparently the OS is running all the time

If you watch them they're very careful how they say that. The line goes: "The display doesn't use any power except when it's changing pages" or something very close to that.

That being said, most people tend to hear that the device uses no power except during page changes, but they're only responsible for what they say, not what we hear.


However, the processor does spin down between page changes, so it does use less power when it's just sitting ("on" or "asleep") than it does when changing pages or processing content.

[schmads]

If you think about it, any electrical device that responds to the user must use some amount of power. In most devices with displays, though, the display uses a huge amount of power, so an e-ink display that removes most of that power usage is wonderful. Yes, people want to believe that the battery will last forever without a page turn, but that just isn't feasible with electronics and batteries and such.

Since it does act as a keylock, it's possible that it is able to save a little power that way, though I'm not sure how much that is. It will also be able to run the CPU at a slower frequency, assuming that is possible. That is mentioned in a prior post.

I saw that in the next firmware version that you'll have the option to make it a full power off, which would be even better. At that point, where it would only power on in response to a single switch, you are at the absolute minimum power draw. Since you're still working with a circuit and batteries, it won't last forever even while turned off, but certainly as long as any other electronic device with batteries.

[igorsk]

The full power off is already in the stock firmware in the 505.

[HarryT]

Originally Posted by KorrMuraan

yeah seems like deceptive marketing

I was also led to believe that the reader only used power to change the page, but apparently the OS is running all the time

Think about it logically. It's a computer with a CPU and memory just like any other computer. Those things require power. The screen only uses power when it refreshes, but the Reader is more than merely a screen.

[Penforhire]

Maybe. Not necessarily like any other computer. Yes, the device has occasion to employ real CPU horsepower (e.g. changing font size). But most of the time this device is (should be) doing nothing more than waiting for a keypress between page flips and doing a memory transfer (from book storage to display memory). There is one more abstraction in terms of converting text (ASCII or other tokens) into e-ink graphics. But that would be best handled by a little chip somewhere, not software -- similar to hardware decoding video signals instaed of software decoding.

The OS here is firmware, not as complex as a normal PC. For instance, the drivers never change (except for firmware updates)! I don't see why it can't have instant-to-human-perception response to a warm start. It may only be a price constraint, like using cheaply-made software decoding instead of designing and producing an efficient hardware decoding chip.

In terms of software/hardware for a reading device I would also be surprised if a page-forward button did not ALSO load the following logical page into non-displayed memory ("page" of a different sense) for fast-and-brainless block transfer to actual display memory on the next page-forward press.

[Nogg]

Originally Posted by Penforhire

In terms of software/hardware for a reading device I would also be surprised if a page-forward button did not ALSO load the following logical page into non-displayed memory ("page" of a different sense) for fast-and-brainless block transfer to actual display memory on the next page-forward press.

I sincerely don't think it does. Since the refresh speed of the display is so slow, there's really no need to cache the pages.

Also, if anyone is interested and unaware, HackBuilder grants users of the 500 access to the full power-off feature that the 505 has available natively.

[HarryT]

Originally Posted by Penforhire

The OS here is firmware, not as complex as a normal PC.

The Reader runs the Linux operating system. Its software is far from trivial although, as you say, rather more compact that one would find on a desktop machine. It certainly goes into a low-power mode while waiting for a key-press, but that's not to say zero-power.