This boot procedure works...but WHY?

[woverst53]

I have an old Toshiba laptop, Satellite A105-S4284, that died a year ago. I replaced the battery, but that didn't fix it. When it boots, its runs Linux Mint Debian Edition, version 5 Elsie, 32-bit. This is now how I get it to boot and this works every time:
1. Unplug the power cable from the back of the laptop.
2. Remove the laptop battery.
3. Press and HOLD down the laptop power button for 60 seconds.
4. Install the laptop battery and latch both slide switches that hold the battery in place.
5. Plug in the power cable on the back of the laptop.
6. Press the laptop power button. This successfully starts the boot sequence.

Now will someone please explain to me why this procedure works...every time I try it? I know I should toss it and get another but I really like this one.

[cretsiah]

dont know why sorry...

we used to have an old win95b toshiba laptop with cd drive .... battery was dead but didnt need it, could remove it and still boot the system..

kinda wish they still made them that way.

[Coggy]

I would guess there's a capacitor across the battery, to allow changing the battery without losing its settings. And holding the power button with the battery out is enough to also flatten the capacitor and lose your rogue BIOS setting, whatever it is.

[coffee412]

When the laptop is off there are about three power rails that are always on. This would be the 3.3v, 19v, and 5v. The power button is 'ground side switched' which just means that the power button always has 3.3v on it. When you push the power button it grounds the 3.3v so you should go to roughly 0v. The real brain of the laptop is the Startup Chip or also called the Super I/O chip. This chip monitors everything in the laptop. The Super I/0 chip monitors the voltage on the power button and when it sees it drop to 0v it turns on the laptop. The sequence is 3.3v to 0v to 3.3v = turn on the laptop.

What you are doing when removing all power and holding the power button down is that you are draining residual voltage from the laptop board and thus the bios has to reload and reconfigure the laptop before it will boot. On older laptops they use a plugin battery of 3v to keep your configuration. Newer ones keep the configuration by using the 3v drawn from the battery.

In a lot of situations the Super I/O chip can get "Stuck" in some laptops. They appear to have power. The power and charge lights light up but it will not turn on. The fix for that is to drain all power from the laptop and then restart it. This resets the Super I/O chip and bios and the laptop turns on.

1. After going thru the procedure you describe to get it to start if you just plug in the battery in will it start up?

If not and your battery does have a decent charge in it then there is a fault on the MB in detecting the charge state of the battery or a connection to the Super I/O is faulty. When you plug in the power cable the signal to the Super I/O is restored and the laptop powers on.

2. If it does start up after resetting power but just under battery power when its plugged in then I would look to see if there is a bios update that might help.

The most common fault on laptops is a failing capacitor. When capacitors die they provide a short to ground. You could have a failed capacitor or other component on the battery 3v line heading to the the Super I/O chip and thus grounding out the start up voltage.

Worst case scenario is a failed Super I/O chip. Most modern ones also hold the bios firmware. While you can replace and reflash the bios to the Super I/O it does involve some work to do. The Super I/O is typically something like 100 pins coming off it to the MB. If you want to pursue this then what I would do is look up the data sheet on the Super I/O and find the pin that signals power on from the battery and test to see if its grounded out. Most likely a capacitor or other component has failed somewhere in the trace heading back to the battery if this is case.

To really answer this in a forum is hard to do without having the laptop on the bench and checking components. Understanding the sequence of the power up of the board is important.

Power button pressed:

1. Super I/O chip checks all power supply circuits for functioning correctly, Chipset, Processor, Video chipset. Any fault and laptop does not turn on or error code is presented.
2. Tests pass = Super I/O then starts processor/chipset/video chipset and tells the laptop to load bios.
3. Laptop loads Operating system.

So, I either just glazed your eyes over or made things much clearer. (?). Anyways, I would bet on two things as possibilities - 1. Your startup chip is not seeing something it should or (2) A flaky bios version that should be updated if possible.

[woverst53]

Thanks!! No glazed eyes yet. Will do more troubleshooting. Your explanation is very helpful.

[coffee412]

Thanks!! No glazed eyes yet. Will do more troubleshooting. Your explanation is very helpful.

1. After going thru the procedure you describe to get it to start if you just plug in the battery in will it start up?

[woverst53]

After going through the procedure I describe, if I plug in the battery, it will not start up!!

[coffee412]

Check your bios version on the laptop and see if there is a newer one. After some thought it sounds like you need to always reload the bios all the time for the computer to start. That is where I would start - not having physical access to your computer.

[AndyMH]

I wonder if a dead CMOS battery might cause this, usually easy enough to replace.

[coffee412]

I wonder if a dead CMOS battery might cause this, usually easy enough to replace.

On modern laptops the battery takes the place of the cmos backup battery. Older models have the watch battery (3v) that can be removed and checked with a multimeter.

I would think that if your cmos battery was bad then it still would not prevent your laptop from powering up with only the battery or power plugged in. It would take longer to boot as it goes thru some initial hardware checks/configs but you would eventually come up to some output on your screen.