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I lost 512MB of RAM.... why?

J

jimmarako

Junior Member
I have an AsRock 939SLI32-eSATA motherboard I'm trying to add memory to. The system has 4 DIMM slots, and claims to support 4GB of memory. I built up the system about 6 months ago with 2x512 (1GB) of Patriot 2-3-2-5 DDR (dual channel kit). The system has run fine with this memory... I even had it running at 2-2-2-5 @2.6V most of the time. According to the boot up screen its says "dual channel" so I think it is working in dual channel mode.

If I run some work at home, it sometimes exceeds 1GB which brings the run time of the system way down. So I've been looking to upgrade. I found an open box deal at newegg on 2x1GB (2GB) Patriot 2-3-2-5 DDR (dual channel kit). So this memory seems to be the same memory as my original memory, just a 2GB kit vs a 1GB kit (both kits appear to be double sides, 16 chips).

When I place the memory in my system, both the boot up screen and Windows claim I know have 2560MB (2.5GB) of memory... so I lost 512MB somewhere (it still says dual channel though). Before I installed the extra memory, I slowed the access back down to 2-3-2-5 with 2T timings. I've swapped the pairs of memories between the slots with no luck. I've changed the timing in the BIOS to 2-3-2-8 with 2T at 2.8V (the higest voltage the MB will do) and still get 2.5GB. I've tried just the 2x1GB kit and it correctly shows up as 2GB.

If you go into the BIOS it will show all 4 DIMMS correctly (2 1GB dimms and 2 512 dimms). I run various mem-test programs (such as everest 3.0) that show speeds consistant with Anand's review of the board (mem reads of ~5500MB/s) and also find all 4 dimms correctly.

The manual for the MB says that pairs of dimms must be same speed, size, make, type, etc.... for dual channel to work. It also claims that if 4 dimms are used they must all be the same speed, make, size,...... Searching the internet seems to say that the pairs of DIMMS do not have to be the same.... so 3GB should be possible. Maybe the MB has an extra restriction?

Any thoughts?
Thanks
JM
 
32-bit systems can only support up to 2.5 gigs of memory. If you throw in any more than that, it'll only detect and use 2.5. so it's not a problem with your mobo, it's just all 32-bit operating systems in existence. If you have a 64-bit cpu and OS, then you have until 128terabytes of ram before it'll stop recognizing it. That's why people say anything more than 2 gigs is a waste.

Text
 
Thanks for the quick reply.

I'm using an AMD Athlon64X2 3800+ (so a 64 bit, dual core AMD). So at a minimum, on the POST screen I would expect all 3GB of memory to be seen since the OS is not involved yet at this point, and surely the processor can address over 2.5GB of memory.

I'm running Win2K SP4 with all updates up to a few months ago. My understanding was that Win2K could not assign more than 2GB of memory (RAM and/or Swap space combined) to any one process. I have actually hit this limit running some Chip synthesis runs. But I thought that 4GB was the total physical memory limit for Win2K (2^32 = 4GB).

I have a WinXP box here at work with 4GB of ram (This is a Xeon based workstation). XP claims to have 2.75GB of RAM. The people setting it up explained that XP doesn't report memory correctly or that it takes some off the top for caching... something like that. I just rebooted that machine and its POST said that it did indeed have 4GB of memory. My Athlon is newer (and probably faster) than this Xeon so again I hope at post it would atleast see the 3GB.

The only other XP box I have has 2GB of memory, and XP reports that machine as having 1.75GB of RAM so there seems to be something funny with the way XP reports memory.
 
Wow, thanks. I guess since my Xeon system here is able to go up to 8GB the chipset/memory controller has that "memory hole" at some other location than the 4GB mark.

I dug around the ASRock site and it seems that they say if you populate the MB to 4GB that it will read as ~3.5GB. So its good to know that I can increase the memory some more at a future dat if I need to.

Thanks
 
OK, I have some more information to give, and another question to ask.

I contacted ASRock's customer support. There is a setting in the BIOS called "Memory Hole". By default this is disabled. I have changed that to enable and Presto!!! on boot up, the POST screen shows a full 3GB of memory. So that problem is partially solved. As far as I can tell from searching the internet, this switch exist on most if not all modern MB's

Here is the odd part now:When I boot into Win2K the computer says I only have 2GB of memory. This is odd becuase when the BIOS was only seeing 2.5 GB of memory, Windows happily said I have 2.5 GB of memory. So there seems to be some kind of "conflict" bettween the HW/BIOS mapping of this memory hole and the OS. Some BIOS's seem to have a Soft and Hard memory hole switch... not mine though.

Are there any Win2K experts that have a solution for this? My quick searches seem to suggest there are way to set switches in the BOOT.INI file, or other patches but I haven't been able to figure them out yet. Many sites have claimed that the Win2K memory linit is actually over 4GB with the "proper" switches.

So I'm one step closer. Worst case I'll disable the memory hole and go back to 2.5GB... thats more memory for the OS to work with. It will be quite a while before I find the $$$ to buy another 2x1GB chunk of RAM to see what changes at the 4GB limit.

Thanks
JM
 
I haven't had much luck getting Win2k to acknoledge/accept my 3GB of memory. Oh well, I guess I need to keep the old google search going. I'd consider upgrading to XP but XP seems to be worst. And there is no way I'm going to Vista64 anytime this decade.... new drivers, new SW, new restrictions from MS... yuk!

JM
 
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