Windows Vista Ultimate 64-Bit Won't Show 4GB of RAM


i'm running a pcchips mobo with a pentium 4 64x duo core proc. and a seagate 320gig hd. 650watt power supply and radeon x1650 pro 16x pci-express video card and 4 gigs of memory. my bios recognizes the memory but windows only shows 2 1/5 gigs
i can remove 1 2gig chip and put in place a 1 gig chip and it shows 3 gigs....
its all same brand and fsb memory what am i doing wrong?
So the BIOS recognizes the RAM but the OS wont. You say it is Vista 64 Bit right? Sounds like the RAM either isnt seated correctly or the OS is not recognizing the RAM. I would think the later. Since they removed the repair feature in Vista it might only be a full re-install that works. Did you ahve all 4GB when you first installed Vista?
Well it could be that the upgraded Memory has caused this issue. Are the memory exactly the same timing wise?

If so it seems like there is something wrong with the install that it is not recognizing the full 4GB. Maybe try a re-install if at all possible to see if that fixes it. I will see if i can find anymore info on this.
What's the southbridge on your motherboard? I know some people with the older 32-bit southbridges have this same problem, despite running an x64 OS.
I was on IM last week with a good geek friend of mine, and he told me about how Vista x64 on his laptop won't see the full memory because of this. I didn't know the Southbridge even had a 32-bit/64-bit option in the first place.
v-link 533 mb/s high bandwidth North/South Bridge interconnect
chipset is a VIA P4M890 Northbridge and VT8237R Plus Southbridge
high performence Northbridge with 1066/800/533 MHZ FSB for INTEL Core tm Duo/Celeron D processors


it is a PCChips P29G motherboard with latest bios update
bios sees 4096 megs
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Well as I said up above it maybe that the update didnt take in Vista. Who knows. Only a re-install would tell for sure if it is a Windows related issue or not. Right now i can not say for sure cause i have heard of this before. Just not this severe. Most of the time it is half a gig gone not 1.5GB lost.
Yeah, I don't think this is the 32-bit issue; because in that case the BIOS wouldn't recognize the full 4GB.
This is most definately caused by the PCCHIPS motherboard. These boards are notorious for being flawed and not working properly to specification. That board only supports single channel DDR2 at 533 FSB, and just because it says it can handle 4GB doesn't mean it will do so properly, especially if the chipset does not know how to map I/O memory (for your video card, sound card, etc.) correctly above the 4GB barrier.

Remember the issue with the MacBook only being able to support 3 GB because it was based on the 945 chipset (which was fixed in 965 / Santa Rosa)? This is essentially the same issue. I've got a 945 chipset notebook, and if I pop 2x2GB RAM sticks into it, the BIOS sees 4GB, but the system itself can only utilize ~2.75 - 3GB.

I'd recommend replacing your motherboard with one such as a Gigabyte GA-P35-DS3 or another decent motherboard based on a 965 or P35 chipset for maximum compatibility in a 64-bit environment.

Side note: I've owned two PCChips based computer systems in the past. And these motherboards suck more than Paris Hilton, if you catch my drift.
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Vista does not see 4GB of RAM

I am having the same problem as PUCK101 except I am using a FOXCONN C51XEM2AA-BEKRS2H motherboard. I have attempted to reinstall Vista Ultimate 64, I have tried switching the RAM sticks, which are the same brand and size, and the system will not run with 4GB installed (two sets of 2 X 1GB). I get the blue screen with the statement saying that windows has shut down to keep your system from being damaged.......etc. I'll take that back I have had it show the 4GB and boot all the way up but the next time it fails. If I remove one stick it runs ok as 3GB but the start up shows that it is running as a single rather than a dual core. Sorry, forgot to mention, I have an AMD X2 64 6000+, 250 GB hard drive, two DVD burners, and a GForce 7600 PCI express video card. The HD and DVD burners are SATA.
Anyone have any thoughts on this?
Thanks, Dan