Aspire 500U Bios problem

I suspect that my Aspire all in one 5600u has a corrupt bios.(i53230m @2.6ghz windows 8.1 1tb hdd 8gb ram)

If you shut it off it will not start unless you reset the CMOS via jumper or you are using 2gb ram.

I did reset the bios via jumper and loaded the defaults - this will restart it and all is almoost normal:

boots to windows and restarts from windows but only if you are using restart - if you turn it off, it will not restart and you can't access the bios (black screen of death) untill you reset the bios again via cmos.

Today I also discovered that if you replace the ram with a 2GB stick it will work normally, it will start anytime even after shut-off not only after a restart.

It doesn't matter which ram slot on the mobo you are using with the 2gb of ram, it will work(this excludes a bad ram slot) but it will not start with a 4gb stick/sticks or 8 gb stick/sticks unless you reset the bios via jumper

Checked the bios battery and it is good, checked all the components and all are working fine.

I tried to reflash the bios from windows and it doesn't complete ( I suspect because is the same version )

Is there a way to force a bios flash direct from an usb stick?

Also if anybody has any pertinent advise it will be highly appreciated

Thank you

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IronFly

Are you sure that the other ram stick (4-8GB) have the same specifications as the 2GB?

Support DDR3 1.5V 1066/1333 (1GB / 2GB / 4GB) dual channel up to 8GB

Supported capacities 1, 2, or 4 GB

Maximum memory 8 GB (using two 4 GB modules)

agpjt

the 4gb sticks are the original ones - bought my computer brand new
the 2gb stick is a kingston pc3-10600s

it will not start with two 2gb, nor with one 4gb, nor with two 4gb, it will work normally just with one 2gb in either slots.

if you clear the CMOS it will start with two 4gb and it will restart until you turn it off from windows or from the power button, then after it willnot start unless you have one 2GB stick or you clear the CMOS again