Disabling switchable GPU - what battery life hit?

I'm considering disabling the switchable graphics option in my T400 to unlock a bit more physical memory (I have the issue that Vista is only seeing 2.5GB of physical memory out of 4GB installed) and wondered what the hit on battery life will be. Anyone have any real life experience?

 

on switchable graphics do you mainly use integrated or discrete?

switchable graphics (discrete) has both integrated and discrete graphics turned on. so just setting discrete in the bios should get you more battery life.

otherwise, integrated setting switchable graphics (integrated) and using integrated in the bios would yield the exact same results.

 

so disabling the switching capability basically makes no difference? I'd set it to use discrete (ATI 3400) all the time.

 

Setting it to discrete permanently is exactly the same as setting it as discrete in Vista through the right-click menu, except that you cannot change it back without a reboot.

So, obviously, your battery life will take a hit as compared to if you had it permanently set to integrated.

 

I changed my T500 Bios to Discrete Graphics and I gained 546MB of recognized physical ram.
I have 4GB ram installed.
I never use my battery for extended periods, so I don't know how big a hit battery life will take.
I changed the following Bios setting.

Config > Display > Graphics Device > change to DISCRETE GRAPHICS

I also think I changed the following, but I don't quit remember for sure.

Config > Display > Graphics Device > OS Detection for Switchable Graphics > change to DISABLE

It took more than one reboot before all 546MB was recognized.

Switchable Graphics Enabled


Discrete Graphics Enabled

 

the discrete gpu uses up to 30W, so of course using it all the time will decrease battery life compared to using the integrated gpu. I use a SSD so it uses very little power and on integrated gpu there is almost never any need for the system to cool itself using the fan. if i switch to the dedicated gpu the fan is needed to keep the system cool. if the needs of the moment do not need the grunt of the dedicated gpu, why use it and its extra power, heat and requirement for cooling? just switch to it when a specific program benefits substantially from it. if you use that specific program all the time, then more ram is used if you retain switchable graphics. similarly, if you never use the dedicated gpu you can gain extra ram by again turning off switchable graphics and using the internal gpu all the time. again, you gain some ram. whether you will see much benefit depends on how much ram you have, how much is being used, whether you have specifically a ram deficit or not, and which OS you are using -32 or 64 bit...If you have sufficient ram, then if you ever need to switch gpu's then being able to switch on the fly is awesome. if you never need to switch gpu's then why bother with switchable graphics? just turn it off and stay with your choice, whichever that is. giving ram to a gpu you never use has no sense, and might just be of a little system benefit...for those of us who switch and have sufficient ram, why switch it off?

 

If you set it on switchable in the bios, but set it to discrete in windows, it supplies power to both the intel and ati card.
However, if you set it to discrete in the bios, only the ati card will be powered. So setting it to discrete in the bios will give you a logner battery life.

 

Alternatively, install an x64 OS and it’ll be able to see all 4GB of RAM.

 

Thanks all... I would switch to a 64-bit version of the OS except some software is still a bit iffy running on 64-bit. I'll tweak the bios and forgo intel's GPU altogeher I think.

 

Which software do you think is iffy? 64-bit OS can run all 32-bit software in a 32-bit mode. The only issues would be if you require drivers for hardware that are unsigned or 16-bit software.

 

I do have some older software... I'll go through and check it'e all compatible. Of course I just bought the T400 with Vista Business 32 so the outlay and installation time for a 64-bit OS is not something I'm considering right away.

One thing I'm curious about... when the switchable option is enabled and the GPUs gobble up a gig of RAM (reducing physical total to about 2.5GB) is any of that "missing" RAM ever released by Vista if it's needed by a program?

The main reason I want to free up more physical memory is because I do a lot of work in photoshop and illustrator, two programs that really benefit from more available RAM.

 

The problem here is an x86 OS can only see a maximum address space of 4GB—and since all your hardware is using ~1.5GB of memory addresses, the additional 4GB of memory address space provided by your memory modules increases the total addresses available to ~5.5GB. Since x86 OSs can’t see beyond 4GB of address space, the RAM beyond 4GB is never “released” because an x86 OS can’t touch it to begin with.