What's the difference between a "hard reset" and powering IPhone 3G off?

What does it do when you do a hard reset as compared to shutting the phone off?

I am curious but since the phone is working fine, ai don't want to do anything to disturb it.

Thanks

The Omega

Thank you. I was looking for something a little more technical like when you power it off it just puts most hardware into a sleep or low power state where as a hard reset actually resets and/or removes power to most/all hardware.

Thanks again for your responses.

Just for reference, the term "powering off" when speaking of cell phones usually means putting the hardware into a low power state but does not reset the devices. Doing a "hard reset" on any computer type device including cell phones usually means actually reseting ALL the hardware on the device.

Thanks to all for your answers.

The Omega

Message was edited by: The Omega

geauxiacerx - I am not sure what your point is here, but I just asked a simple question, and although I will admit that your response of - Posted: Aug 18, 2008 8:22 PM was helpful, it is obvious to me that you don't know what the technical difference is, and neither does the other respondent who did all the complaining. No one asked him to respond more than once to my question.

I made it clear, in what was to be my last post in this thread, before you made your non-useful and unnecessary comments, that the difference technically is that a hard reset actually resets ALL the hardware and thus will cause it all to restart whereas "powering off" just puts many of the devices into a lower power state but does not actually reset any devices. So when you turn it back on, it just "wakes up" but has not actually been reset (did not go through all it's normal boot sequences when woke up).

It is like putting your computer to sleep (powering off the IPhone 3G) and pushing the reset button on your computer (doing a hard reset on the IPhone 3G). What I was looking for was specifics about the IPhone 3G, a device I am not that familiar with, that might be different from the norm.

The Omega

Dr Sly; Thank you for your response. To better help anyone who is curious about this, most every device within the IPhone 3G, the CPU, radios, some amps, etc. have a pin on them that is called "reset". What this pin does is when it is driven active (to ground in most cases) all the internals (registers) within the device get set back to their default values when they were first powered up or first programmed. Many devices also have the capability to run at lower voltages and to have their clocks shut off to save power.

A "hard reset" resets most all the hardware devices (CPU, GPU, Raidos, etc.) to their default states and the CPU starts code execution at it's default startup address. When you power the IPhone 3G "off", by holding only the sleep/power button, it causes many of the devices to have their voltages lowered and their clocks shut off, which saves power. When you turn the phone back on, they simply have their voltages raised to normal operating levels, their clocks turned back on, and they are in the same state they were in before you held the sleep/off button.

So, the difference is that holding the sleep/power button only reduces the power the devices use, and when powered back on the phone is in the same state as it was when you powered it off. This is similar to what is called suspend to ram, which is supported in most laptops today. When you hold down both the sleep/off button and the home button this cause all devices to be reset and to start up from their default states. Any volatile memory will be lost in this case. This is what prompted my question.

Thanks again for your input.

The Omega

A "hard reset" resets most all the hardware devices (CPU, GPU, Raidos, etc.) to their default states and the CPU starts code execution at it's default startup address. When you power the IPhone 3G "off", by holding only the sleep/power button, it causes many of the devices to have their voltages lowered and their clocks shut off, which saves power. When you turn the phone back on, they simply have their voltages raised to normal operating levels, their clocks turned back on, and they are in the same state they were in before you held the sleep/off button.

So, the difference is that holding the sleep/power button only reduces the power the devices use, and when powered back on the phone is in the same state as it was when you powered it off. This is similar to what is called suspend to ram, which is supported in most laptops today. When you hold down both the sleep/off button and the home button this cause all devices to be reset and to start up from their default states. Any volatile memory will be lost in this case.

rimshaker; You make some good points regarding the cell network and how it reacts to the phone connecting to the network.

As to your statement here - "On your computer, there's no difference between pushing the reset button or pushing the power button. The startup process is the same.", this is not completely true. When you push the reset button the BIOS knows that power has not been removed and skips setup stuff it does when power is lost because there is no need to re-execute it. When you power the computer completely off, the BIOS runs through the entire initialization. I have worked on issues on new designs that only occurred with one but not the other. There is a difference.

If you are more comfortable with being sure that "...the iphone has been properly reset....", then you want to do a hard reset. Powering the phone down by holding only the sleep/off button for 6 seconds likely does not reset anything.

Thanks

The Omega