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Discussion Starter · #1 ·
XP doesn’t read ram correctly, but BIOS does.

Here’s a weird situation, system has 4 gigs of ram and the BIOS reads it correctly as 4095MB. But XP Pro reports only 2 gigs. Anyone got a clue why this would happen? I’m going to try a swap out when I can get my hands on a couple of one gig modules for testing, but that’s not going to be for a few days. Advice would be much appreciated.

Some system details below. I can get more when I crack the box open.

System:
OS: XP Pro SP1
MB: Supermicro Dual Xeon 266
Mem: 4x 1gig modules. Matched set, so I’m told. Type unknown. ECC???
BIOS: Phoenix

Potential items of note:
In the BIOS under advanced chipset control there is an ECC config selection. I see only two choices – ECC or Disabled. Currently set to ECC. The item specific help says “If all memory in system supports ECC, this selection selects from: No ECC, Checking Only, Checking and Correction or Check correction with Scrubbing”. Does the lack of the four choices in this case mean the ram is NOT ECC?

In OS now - Device manager -> System Devices -> Direct Memory Access Controller. Properties notes “No drivers installed” but the driver tab notes 5.1.2600.0. Tried a driver update, but got a “no better driver than the one installed yada yada…” message. Is that normal? Probably not related, but I thought I’d mention it. There are no attention warnings anywhere in device manager.

Generally the system is running well, with a few shutdown/reboot errors that I attribute to Roxio EZCD Creator not being properly removed (I know about the regedit and will fix it one day) but it’s most important to have all 4 gig pulling their weight for CAD work first.

Thanks for any advice!

<My first posting here - please excuse me if minimal details are prefered to save space>
 

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Most memory is not ECC, so I suspect that's what you're seeing.

Exactly what CAD application do you use that requires 4gigabytes of RAM? In almost every case I've ever seen, memory past 1-2 gigabytes is wasted and doesn't add any performance...
 

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Discussion Starter · #3 ·
SurfCAM. Writing tool paths on huge assemblies (for CNC machining) is VERY ram intensive.

So you think if I "Disable" ECC in the BIOS config it will solve the problem? Will try that now and let you know the result......
 

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Discussion Starter · #4 ·
Nope - the OS is still reporting 2 gigs, the BIOS 4 gigs.

If it wasn't for the BIOS, I'd assume half the memory was bad, not seated correctly or not compatible with the other half. Since the BIOS knows, I was hoping it was a simple OS setting to make it recognize.

Anyone have a clue as to what could be causing this discrepancy?
 

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I'd download www.memtest86.com and run it overnight, just to eliminate memory as an issue. It boots from the floppy, so it should see the memory if it's detectable. The floppy is a Linux kernel that just runs the memory test.
 

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Discussion Starter · #6 ·
OK. I downloaded it and skimmed the extensive readme. Looks pretty straightforward, so I'll run the test overnight and see what it discovers.

Will post a message with the findings tomorrow. Thanks so much for the pointer!

In the meantime, if any one else has any thoughts, please let me know. I'll be online via laptop while the workstation labors all night on the memtest. Looks like it'll take quite some time......
 

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If it's running error-free, and has detected all of the 4gigs of RAM, I'd say the RAM is working. :)

If that is the case, it must be an XP issue. I see that XP is supposed to support 4gigs, but maybe there's a setting that needs to be tweaked to get it to recognize all the memory, never had more than a gigabyte myself...
 

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Discussion Starter · #9 ·
Yea - that's what I thought. The test recognises all 4 gig's and there are no errors yet. It's up to 37 hours now and still running.

Anyone know what OS setting needs to be tweaked?????
 

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Discussion Starter · #10 ·
Ha - found it! It is on OS setting! You might want to add this info to your personal knowledge base:

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

****************************
The virtual address space of processes and applications is still limited to 2 GB unless the /3GB switch is used in the Boot.ini file.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINNT="????" /3GB

*****************************
 

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Thanks, makes sense that it's an XP thing... :neutral:
 

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Discussion Starter · #12 ·
Unfortunately it didn’t work as promised by the Microsoft documentation. More research for me, unless someone else has a clue…
 

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I don't think many folks are trying to use more than 2gigs with XP, so this isn't a widely researched issue...
 
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