Hi Chuck,
I have seen this type of thing before (on Windows 2000 and XP) on different
systems. While I don't have a full explanation of exactly why this happens,
I believe it has to do with addressing on a 32 bit processor. Now you may
wonder why I say 32 bit processor when your processor is 64 bit capable.
Unless you are running a 64 bit operating system, the processor is running
in 32 bit mode only.
A 32 bit processor has a maximum addressing space of 4GB, since it uses 32
bit pointers. While it may seem logical to be able to put 4G of memory in
such a machine, the reality of the matter is that you can't use the full 4G
address space to address all the memory. There are other things that require
address space as well, mainly the hardware devices. This would be all
peripherals, including disk controllers, network controllers, video
adapters, etc. It doesn't matter if they are onboard or not.
The devices have top priority in getting address space assigned to them, on
a typical system this could easily be up to 1G of address space. Since the
memory and the devices cannot occupy the same physical address space, some
of the memory must be masked or mapped around the physical devices. I
believe it is this mapping that results in the slowdown.
In these situations, I have had good luck by installing only 3G of memory.
You won't miss it since even with 4G of memory installed, you can only use
at most 3G of it anyway. Another option is to install a 64 bit OS which
increases the address space by orders of magnitude. However, you may have
difficulty locating all the device drivers (device drivers MUST be native 64
bit), some applications may have problems, and those that run may actually
slow down slightly due to 32 bit thunking required to get them to operate in
a 64 bit environment under WOW64.
Russ Poffenberger
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-----Original Message-----
From: Personal Computer Hardware discussion List
[mailto:[log in to unmask]] On Behalf Of chuck
Sent: Saturday, October 25, 2008 5:56 PM
To: [log in to unmask]
Subject: [PCBUILD] RAM slows Vista
My system is slowing down when I add more RAM. I upped it to 4 GB and
everything slowed measurably.
The system is:
Intel Core 2 6400 @ 2.13GHz
Intel DG965OT MB
2 GB DDR2-533 SDRAM (Hyundai)
NVIDIA GeForce 8800GT 512 MB
Vista Ultimate, SP1
At first I added 2 Kingston Value RAM DIMMs with the original Hyundai DIMMs,
then tried 4 KVR's to make sure it wasn't different manufacturers. I'm
beginning to wonder if there's not a problem with DIMM slots 2 & 4. As soon
as I returned to the original DIMMs, everything was fine. Am I missing a
BIOS setting?
When I have a minute, I'll switch and just use slots 2 & 4 to see if that
replicates the problem.
Thanks for any advice you might have on this.
Chuck Finnigan
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