Member Avatar for ggeoff

Hi

I have a Dell Precision workstation 490 and increased the initial one GB ram (two 512MB sticks) to five by adding two 2GB sticks after I upgraded the op system to Windows 7 Pro 64bit and I have installed the most recent BIOS. There was no problem, the system recognized five GB of memory.

I have bought two 4GB sticks and added them. The system in Setup now only recogizes nine GBs. I took all the memory out and reinserted the two 4GB sticks to check. The system reported no memory fitted! I took them out and reinserted the two 2GB sticks together with the two 4GB sticks. The system now lists four 2GB sticks of memory when it should be twelve the total installed memory is 4GB though.

Is there something wrong with the 4GB memory sticks? They were bought secondhand. All the memory is ECC FBD

The Dell has eight memory slots. The slots are marked as different by having four slot retainer clips cream and four black. I could understand that each "bank" might need four similar sized memory sticks, but then the Dell manual doesn't mention that.

I ran memory diagnostics and all the memory is OK. System Information reports 8GB installed memory but total physical memory 4GB. Available physical memory 3.05GB Available virtual memory 7.99GB and Available virtual memory 6.96GB

From Control Panel > system View Basic Info: Installed memory is reported as "8.00 GB (4.00 GB usable)"

Geoff

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A few focused points that clarify what can cause the symptoms shown in this thread and a short, practical test plan to isolate the problem.

The Precision 490 uses Fully‑Buffered DDR2 (FB‑DIMM) memory and expects modules to be installed in matched sets. For best behavior the board requires matched sets of four (matched in size, rank and organization) and the DIMMs must be populated in the board’s labelled order (matched sets into DIMM slots 1–4 first, then 5–8). The manual also calls out heat‑spreader and population rules for higher‑speed DIMMs — these are common causes of strange detection behavior. Dell Precision 490 User’s Guide

Quick diagnostic checklist (do these one at a time, in order):

  1. Consult the system‑board labels and install a single new 4GB DIMM in the first labelled DIMM slot; boot and note whether the BIOS sees it.
  2. Repeat with the other 4GB stick (same single‑slot test).
  3. If each stick is seen alone, try them as a matched pair in the pair population order the manual prescribes, then add the 2GB modules in the correct order.
  4. If a stick is not seen alone, the stick is likely incompatible or faulty — test that stick in another known‑good Precision 490 (or have the seller test it). Use Dell Diagnostics or memtest86 for additional validation. For basic single‑slot isolation steps see Dell support/community guidance. (Testing single slots is a standard step to detect bad DIMMs or bad slots.)

If Windows reports “installed X GB (Y usable)”: that can be a 32‑bit OS limitation or an address‑space reservation issue; 32‑bit Windows cannot address more than ~4GB. On 64‑bit systems, also check BIOS options (memory remapping / hardware remap) and confirm the OS is actually 64‑bit via msinfo32. Physical memory limits (Microsoft)

Practical note: FB‑DIMMs are pickier than ordinary unbuffered DIMMs — buy matched kits of four (same vendor/part number, same rank/organization) and insist on return/testing by the seller if behavior is odd. See the Dell manual for the exact slot order and matching rules.

Member Avatar for ggeoff

Hi

I have a Dell Precision workstation 490 and increased the initial one GB ram (two 512MB sticks) to five by adding two 2GB sticks after I upgraded the op system to Windows 7 Pro 64bit and I have installed the most recent BIOS. There was no problem, the system recognized five GB of memory.

I have bought two 4GB sticks and added them. The system in Setup now only recogizes nine GBs. I took all the memory out and reinserted the two 4GB sticks to check. The system reported no memory fitted! I took them out and reinserted the two 2GB sticks together with the two 4GB sticks. The system now lists four 2GB sticks of memory when it should be twelve the total installed memory is 4GB though.

Is there something wrong with the 4GB memory sticks? They were bought secondhand. All the memory is ECC FBD

The Dell has eight memory slots. The slots are marked as different by having four slot retainer clips cream and four black. I could understand that each "bank" might need four similar sized memory sticks, but then the Dell manual doesn't mention that.

I ran memory diagnostics and all the memory is OK. System Information reports 8GB installed memory but total physical memory 4GB. Available physical memory 3.05GB Available virtual memory 7.99GB and Available virtual memory 6.96GB

From Control Panel > system View Basic Info: Installed memory is reported as "8.00 GB (4.00 GB usable)"

Geoff

I returned the memory to the supplier who tested it in a 490. One of the memory sticks was defective. He is sending out a replacement.

Member Avatar for yoakim

Normally this indicates that you are running a 32bit OS not 64 ie XP or Win7

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