I can't get 8GB of RAM to boot up.

[Judge Zetsumei]

I have just bought 2 sets of 2x2GB corsair ddr2 pc6400 5-5-5-18 1.8v ram. I put them in my gigabyte GA-P35c-DS3r motherboard and my computer starts but when it gets to the vista loading screen it just never ends. The bar just keeps going accross and it never gets to the desktop. If i take 2 of the modules out so i only have 2 x 2GB, it then boots up.

I am using vista 64bit.

Can anyone help?

[Judge Zetsumei]

Update: Vista has FINALLY started up and got to the desktop but it is extremely slow, both my cpu cores are maxed out to 100% constantly. This doesn't happen with just 2 of the RAM modules in (4GB)

[Agent]

What process is using the CPU up?

When installing new RAM, I always do a preOS test with Memtest+ to make sure its fairly stable before hand.

[Judge Zetsumei]

no process is taking it up, they are all looking normal yet the cpu usage is still 100%

I think i may have a bad stick of ram though. I took one stick out so i have 3 x 2GB and it works fine, i am now going to try that one stick on it's own and see what happens. Thanks for the reply.

[Judge Zetsumei]

The one module on it's own worked fine. So i then tried all four again and i'm back to square one. With all four modules in cpu usage is at 100% from the moment windows begins to load, that is probably why it's taking so long to load.

Properties in my computer say i have 8GB installed so that's fine, and it also says it in task manager so my computer is seeing all the ram, but like i said for some reason when all four are installed it is making my cpu go to 100% constantly. This is very strange, Anybody got any ideas?

[Lucio]

Are you sure you've got the correct voltages? Also there's probably an option you need to turn on in the bios, look for something like PAE extension or similar

[Agent]

If the OS is seeing the 8GB, PAE isn't an issue here. It'll also be "memory hole" or close.

[Dreaming]

I dunno if you need PAE under 64 bit...?

[Agent]

edited - see below for clarification.

[Lucio]

Could be really simply actually, now I read the problem properly

http://www.incrysis.com/forums/viewtopic.php?pid=211632

This indicates that Superfetch seems to go wrong with 8GB of RAM sometimes...

http://www.howtogeek.com/howto/windo...windows-vista/

[Paul Adams]

I dunno if you need PAE under 64 bit...?

Correct, there is no PAE for 64-bit systems, their native maximum address space is 2^64 so does not need a hack to make it 2^36 - that only applies to 32-bit operating systems.

It sounds more like an issue at the hardware level tbh - chipset or BIOS support (or lack thereof).
I have run XP x64 on a system with 4GB installed and the BIOS only let the OS see 3.xGB, which is clearly a problem with the hardware so I returned the motherboard for a different model as there was no BIOS update available for it.

What happens if you boot from the Vista DVD with 8GB installed?
Is that also slow, and can you get into the WinRE?

[Agent]

Correct, there is no PAE for 64-bit systems, their native maximum address space is 2^64 so does not need a hack to make it 2^36 - that only applies to 32-bit operating systems.

There is no PAE to disable, but is that because 64-bit (x86 based here) is built with PAE already being present?
I hate to quote Wikipedia but it says:

On x86-64 processors, PAE is obligatory in native long mode; presently 40 bits are used out of 52 bits possible

With a link to the Intel 64 and IA-32 Software Developer's Manual (1).

[Paul Adams]

I should have been clearer by stating "there is no PAE switch for 64-bit operating systems, any OS which runs natively 64-bit cannot operate without the PAE bit set, hence there is no way to disable it".
(It's just easier to say "there is no PAE" )

(PAE == 0) & (CPU mode == x86) = 2^32 bytes addressable (4GB)
(PAE == 1) & (CPU mode == x86) = 2^36 bytes addressable (64GB)
(PAE == 0) & (CPU mode == x64) = invalid configuration
(PAE == 1) & (CPU mode == x64) = 2^40 bytes addressable (1024GB - currently artificially capped to 128GB for Windows)

Will be interesting if we ever need to expand beyond 40 bits for memory addressing... 2^52 = 4,194,304GB
The good news is that Windows would only need a kernel update for the 64-bit version to accommodate extra bits if they become used.

[Agent]

I thought I was going mad for a moment there and went on a Googling spree in case I'd made a tit of myself

Thanks as always Paul for putting it so well

Will be interesting if we ever need to expand beyond 40 bits for memory addressing... 2^52 = 4,194,304GB

I always wonder how quantum computing will alter the way we think / use memory. We often hear how these magical processors will allow insane processing speeds, but never the parts which will support them?

[Thorsson]

Getting back to the issue itself, which I agree is hardware. OP, try putiing 3 different sticks in but make sure use the memory slot that the "problem" stick was in. I'm thinking it may be a motherboard memory slot fault.

[Lucio]

I always wonder how quantum computing will alter the way we think / use memory. We often hear how these magical processors will allow insane processing speeds, but never the parts which will support them?

Or, more likely, the programing will be less than perfect due to the need to support legacy methods of working and will never reach their full potential.