Vista - Ultimate 64 not functioning with 8G ram

Hi Folks,
My machine works well with 4G ram, but I use lots of memory hogging apps at once, as well as virtual machines, so I thought I would try another 4G ram.
MB is P35DS3R and I have 4 sticks of 2G A-Data 800. As soon as the extra ram is put in, the machine takes a very long time to boot and is functionally unusable.
In msconfig > Boot Advanced Options, Maximum memory is unticked. If I tick it, 4096 is the figure which cannot be increased.
I have borrowed and tried other ram, and checked all the slots, but no joy.
Thanks for any help.

Try checking the ram power setting..that board puts out 1.8v and your RAM
uses 1.85...you should be able to up the voltage to 1.85
peter

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"innecesario" <innecesario.359kp1@xxxxxx-mx.forums.net> wrote in message
news:innecesario.359kp1@xxxxxx-mx.forums.net...

You may need to reduce the dram speed to 667 to use all four dimms. Try it.

"innecesario" <innecesario.359kp1@xxxxxx-mx.forums.net> wrote in message
news:innecesario.359kp1@xxxxxx-mx.forums.net...

I found the same as Colin. To get 4 x 2GB modules of DDR2-800 stable on my
system I had to manually assign the 667MHz ram speed in the bios.

Also check your bios for a setting related to enabling memory mapping. If
the bios is seeing all 8GB but Windows only sees 3-4GB, that bios setting is
a likely cause. On my Vista-64 system with 8GB installed ram, the msconfig
option allows me to go up to 8192 as the max memory limit.

"Colin Barnhorst" <c.barnhorst@xxxxxx> wrote in message
news:92CFA646-593E-479C-A512-C4FD8DD52B11@xxxxxx

[quote=Colin Barnhorst;623584]You may need to reduce the dram speed to 667 to use all four dimms. Try it.
I can't find any way of reducing the speed in BIOS.

What is the mobo? Most support adjusting the dram speed.

"innecesario" <innecesario.359rn1@xxxxxx-mx.forums.net> wrote in message
news:innecesario.359rn1@xxxxxx-mx.forums.net...

Thanks for all your replies, I'll have to get around to finding out out how to use the multiple quoting in this group. But for now,being busy tearing hair out, I'll say that the MB allows 0.1V increase in Ram voltage, I've done that, and I can't find Memory Mapping settings.
I should also mention that I have Dual-booted with XP 32-bit, and with the 8G crippling Vista, XP is unaffected.
Graeme

The problem may be that the memory controller is doing 32bit dma even with a
64bit OS. That is what happens with some chipsets. The memory controller
is getting overloaded. Rather than increase the memory voltage, go the
other way.

"innecesario" <innecesario.359sc1@xxxxxx-mx.forums.net> wrote in message
news:innecesario.359sc1@xxxxxx-mx.forums.net...

I found out how to reduce the RAM speed. So with RAM speed at 667 and voltage at 1.9V it still doesn't work!
Any more ideas?

Then you need to get on the mobo manufacturer's user forum for your mobo.
The users there are very expert. You still didn't say what mobo you are
using so that's about all I can suggest.

"innecesario" <innecesario.359tqc@xxxxxx-mx.forums.net> wrote in message
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