iMac shuts down in bootcamp!

[The-Pro]

Greetings,

I have a 2012 27" iMac with the 675MX and the standard 1TB drive.
Recently it has started being really annoying by shutting down without warning.
The iMac is being used for the occasional gaming at the moment and I have noticed that usually there is considerable frame lag and then just off, but sometimes it turns off when you least expect it.
Once its off the power button doesnt do anything and the only way to get it to turn back in is to do SMC resets over and over and over again.
Last night I needed about nearly 30 SMC resets.
When I reset the SMC I see the lights from the mouse come on quickely and when the reset didnt work the lights dont go on.
So it tries to start up for a split second then it fails. At oke point in manages.

I ran memtest to check the RAM and it passed.
Disk utility and windows disk management thing hasnt found any error with the Harddrive.
Apple Hrdware test passed aswell.
I manually increased the speed of the fan as I thought it must be overheating but with the fan at 2400rpm it really shouldnt be shutting down due to overheating.
I have windows 10 installed.
It does not seem to happen under OSX.

Anyone out there experienced anything similar or knows something I could check?
Its really frustrating

cheers

 

[The-Pro]

little update
it has now decided to shut down in the middle of booting up into osx.

hope the imac isnt toast

oh i noticed im not actually resetting the smc.
what i am doing is unplugging power cable, press and hold the power button for 10secs then plugging back in and trying to turn on.

apple says to reset the smc unplug. wait 15secs, plug in, wait 5 secs, turn on.
But this doesnt seem to do anything.

What does the method im using actually do?? its the only way to get some life out of the imac

 

[AlexisV]

Don't rely on Memtest. Try swapping the RAM sticks because all the problems you have could be attributed to faulty memory.

 

[The-Pro]

Don't rely on Memtest. Try swapping the RAM sticks because all the problems you have could be attributed to faulty memory.

thanks for your reply
I ran the extended Apple hardware test and no faults were detected aswell.

ill put in the original ram that came with the 2012 MBP I have, 2x 2GB
Wouldn't the iMac make some sort of sound if its a RAM problem?

 

[AlexisV]

Dodgy RAM can give you random freezes and restarts, so see what happens

 

[The-Pro]

Ill try other ram and other RAM slots

 

[The-Pro]

Dodgy RAM can give you random freezes and restarts, so see what happens

So I put in 2x 2GB sticks and in the other ram slots. played a game for about 30 minutes then I got heavy frame lag and it shut down.
It was loading in a new area of the map and i was running the game of an external ssd.