# [SOLVED] Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)



## 80MattyC08 (Jul 2, 2012)

Hello,
I have upgraded my acer aspire twice, in the past year with more up-to-date components to allow it to play high end games better. 
Firstly, I removed the ATI Radeon HD 4850 and Gave it a ATI Radeon HD 6870.
Then, I removed the ram and gave it the Corsair Vengence 16gb Dual Channel DDR5 kit. 
However, I have noticed that the computer runs very slow now, and when using task bar, it says that the total physical memory is 3062mb. Cached is 1883mb and the amount free (which changed a lot) is between 52mb and 20mb.
However when viewing system specs though control panel, it shows i have all 16gb installed. 
This has caused significant problems in being able to perform even the most simple tasks as most the time the ram usage is between70% and 98%!
Thanks for your time.


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## gcavan (Aug 13, 2009)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*



> gave it the Corsair Vengence 16gb Dual Channel *DDR5* kit.


No such animal commercially available today. I expect you mean DDR3.

How is the 16GB configured? ie 4 x 4GB or 2 x 8GB
Either case would be a problem as your PC runs system RAM in a triple channel configuration supporting a maximum of 12GB on 6 DIMMs.


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## Tyree (May 10, 2009)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Try using the original RAM and see if that resolves the problem.
As staed above, your Mobo is Triple Chanel and using 3 matched sticks will yield optimum performance.


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Ahh ok.. Sorry, thought it said ddr5, my bad. 
iTS 4X4gb memory... so.. best to get a triple channel memory kit then? I'll try the old ram again and see if it works first. 6gb is better than 3 haha!
Thanks guys for your fast response


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

-It appears that after I have installed the original RAM, there is no change. The task manager is still saying 3062 total physical memory (mb).
I placed them in the white slots. 
A side note, When i turned it on after i put the original ram in, the computer did not get the beep upon start up and none of the lights came on,even tho it sounded like it was running. Second start up it worked but still no ram change)


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## Thrall (Feb 19, 2011)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

This may be a silly question but I just have to ask. Do you have a 64 bit version of Windows Vista or a 32 Bit version? Because if you have a 32 bit version it will not show more then 3 GB. 

I see by the specifications of your Acer that it says it should be delivered with a 64 bit Windows Vista but it says it varies by model so it may be possible you only have a 32 bit version. If you do have a 64 bit version then I am sure the others can help you better.


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## Tyree (May 10, 2009)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Remove all RAM, clear the CMOS, install the RAM and see what shows.
If all of the 4GB sticks are identical Brand/specs, you could try using 3 of them for Triple Channel.


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Ok, I am using a 64 bit system, (just double checked in system specs) so It can't be that but i should have mentioned that initially, sorry.
Since the 4gb cards are all identical, i tried setting them up like a triple channel, but it didn't work either. 
How do you clear the CMOS? Will doing so, affect anything i have save on this computer?


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## gcavan (Aug 13, 2009)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

I'm not sure your system even supports 4GB DIMMs. According to the spec sheet, it supports a maximum of 12GB on 6 DIMMs. That tells me it probably only supports up to 2GB modules.


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

ahh... so if i wanted more ram, I would need more 2gb cards rather than the 4s i bought... dam haha! Wish i registered on here when i was choosing upgrades last year =/


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*



Tyree said:


> Remove all RAM, clear the CMOS, install the RAM and see what shows.


Using a selection of websites as instructions, I managed to access my CMOS or BIOS (not sure which) menu and there was a load default option that one of the forums on here said to click as one of many names for resetting the CMOS. I selected it, restarted (saved too) and logged in. There is no change.
Am i doing something wrong with the CMOS reset?


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## 6082012 (Jun 16, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

On your board is a small CMOS battery, about the size of a nickel. It will have a small latch on it, push it and the battery will pop out. Then take a small metal blade and short the two contacts for the battery for 10 seconds, this will clear your BIOS setting, clock and CMOS, but won't affect any of your data. 
There may be a jumper on board labeled CRL_RTC or CLR_CMOS or similar. You would remove the jumper and switch it to the other two pins next to it, which does the same as the battery operation.

It may be a good idea to get a new battery, it should be a 2032 which you can get almost anywhere.


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*



Britton30 said:


> On your board is a small CMOS battery, about the size of a nickel. It will have a small latch on it, push it and the battery will pop out. Then take a small metal blade and short the two contacts for the battery for 10 seconds, this will clear your BIOS setting, clock and CMOS, but won't affect any of your data.
> There may be a jumper on board labeled CRL_RTC or CLR_CMOS or similar. You would remove the jumper and switch it to the other two pins next to it, which does the same as the battery operation.
> 
> It may be a good idea to get a new battery, it should be a 2032 which you can get almost anywhere.


Ok, i found what i think is the cmos battery (was very well concealed beneath my graphics card) and I am uploading this pic just to check if it is the right one:








also, there doesnt appear to be a battery latch pin... unless u can see it? 
Excuse the bad quality image... had to use laptop camera


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## 80MattyC08 (Jul 2, 2012)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Ok, thanks for all your support guys, however in the end, i went to a local pc repair shop. As it turned out, one of the RAM cards had burnt out. So it has been replaced 
Thanks for all the help though, Next time i have a problem, I know where to ask first


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## Tyree (May 10, 2009)

*Re: Computer only detecting 3gb of 16gb RAM (Acer aspire m7720 12gb DDR5 RAM)*

Glad you got it resolved and thanks for posting back.


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