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PiterMcFlebor

1 Rookie

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2 Posts

41

May 14th, 2025 09:48

Dell Precision T3500 RAM size issue

Hello,

I got a Dell Precision T3500 for free and I want to use it as a cloud server but it came with 6GB of RAM only so I bought 6x4GB DDR3 RAM non-ECC unbuffered and then installed Ubuntu Server 24.04 LTS.

The mobo has a W3520 installed.

The problem is when I boot up the system kernel is only detecting 16GB of RAM usable but when I check the hardware installed it shows up that there's 6 modules of 4GB having a total of 24GB.

My questions are:

- the Dell Precision T3500 has any limit? I read that the limit of the mobo is 24GB but that's because of only allowing 4GB modules.

- the CPU itself has any limit? Searching about it looks like it doesn't have any limitation like this.

- how do I fix this?

Thanks in advance.

anne_droid

3 Apprentice

 • 

660 Posts

May 14th, 2025 22:10

Hi

I believe so.

The limit is 24 GB in "TRI" mode.

24 DR 4 GB 4 GB 4 GB 4 GB 4 GB 4 GB Tri

Kingston offers "K3" kit part numbers for Triple Channel mode.

So I can only suggest that you research this TRI mode, and perhaps check the BIOS settings for any clues.

It may just be that all 6 modules have to be identical.

https://www.mrmemory.co.uk/memory-ram-upgrades/dell/precision-workstation/t3500?search=Dell+Precision+T3500

PiterMcFlebor

1 Rookie

 • 

2 Posts

May 19th, 2025 13:38

@anne_droid​ 

Hi,

I replaced the CPU to a W3690 also all my RAMs all exactly the same as I bought all of them at the same time from the same seller.

BIOS is detecting the 24GB, the CPU-X (CPU-Z for Linux) is detecting all 6 DIMMs with RAM.

These are my installed RAMs:

  >>>>>>>>>> Memory <<<<<<<<<<

        ***** Stick 0 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 1          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8241 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

        ***** Stick 1 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 2          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8242 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

        ***** Stick 2 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 3          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8243 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

        ***** Stick 3 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 4          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8244 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

        ***** Stick 4 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 5          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8245 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

        ***** Stick 5 *****
    Manufacturer: 80AD000080AD    
     Part Number: HMT351U6CFR8C-H9  
            Type: DIMM DDR3
     Type Detail: Unbuffered (Unregistered)
  Device Locator: DIMM 6          
    Bank Locator: Not Specified
            Rank: 4
            Size: 4 GB
           Speed: 8246 MT/s (configured) / 1333 MT/s (max)
         Voltage: 8.224 V (min) / 8.224 V (configured) / 8.224 V (max)

clintonsnow

1 Rookie

 • 

83 Posts

May 21st, 2025 18:01

Here's a breakdown of your Dell Precision T3500 RAM issue:

✅ Summary of Your Situation:

  • System: Dell Precision T3500

  • CPU: Intel Xeon W3520

  • RAM Installed: 6 × 4GB DDR3 Non-ECC Unbuffered = 24GB

  • Detected by OS: Only 16GB usable

  • BIOS/Hardware view: Shows all 6 × 4GB sticks installed

🔍 Analysis:

1. RAM Type Compatibility

The T3500 officially supports ECC registered memory or non-ECC unbuffered memory, but you should not mix ECC and non-ECC or buffered and unbuffered modules.

✅ You mentioned using non-ECC unbuffered, which should work, but Dell systems are picky. Some motherboard BIOS versions don't fully support all types of unbuffered memory, especially in all 6 slots.

2. CPU RAM Limit

The Intel Xeon W3520:

  • Supports up to 24GB DDR3 officially.

  • Realistically, it should support up to 3 DIMMs per channel (6 total) × 4GB = 24GB, which matches your setup.

  • So, the CPU is not the bottleneck.

3. Motherboard & BIOS Limits

The Dell T3500's motherboard:

  • Supports tri-channel DDR3.

  • Works with ECC registered and non-ECC unbuffered, but not all brands/models of non-ECC RAM are fully compatible.

  • Max memory depends on type and configuration:

    • ECC Registered: Up to 24GB

    • Non-ECC Unbuffered: 24GB may work, but not always reliable in all 6 slots

Additionally:

  • BIOS version matters a lot. Outdated BIOS may cause incorrect RAM mapping or limitation.

How to Fix or Diagnose:

Step 1: ✅ Update BIOS

  • Go to Dell's official site and update your T3500 to the latest BIOS version (A17).

  • Older versions had memory detection bugs.

Step 2: 🧪 Test RAM Slots & Modules

  • Boot with only 3 × 4GB sticks (one in each channel) and check total RAM.

  • Then add one by one to verify if a specific slot or module causes the issue.

  • Try rearranging them across channels. Example:

    • Channel A: 4GB (Slot 1)

    • Channel B: 4GB (Slot 2)

    • Channel C: 4GB (Slot 3)

    • Add the remaining sticks in the second bank of each channel (Slot 4–6)

Step 3: 🧰 Check Memory Remapping

  • Enter BIOS setup and look for an option like "Memory Remap Feature" or "Memory Hole Remapping".

  • This should be enabled to allow full access to RAM above 4GB.

Step 4: 📋 Check with dmidecode

Use the following command in Ubuntu to confirm what Linux sees:

bash
Copy Edit
sudo dmidecode -t memory

Also check:

bash
Copy Edit
free -h

and:

bash
Copy Edit
dmesg | grep -i memory

This may show messages like "Memory above 16GB not used" or ACPI mapping errors.

🔁 Optional Workaround

If nothing works and you're stuck with 16GB, you could:

  • Use ECC Registered memory (e.g., 6 × 4GB ECC REG DDR3) which is known to work well on the T3500, especially with the Xeon CPU.

  • Sell the non-ECC and swap to ECC REG (often cheap second-hand for workstation/server builds).

🧠 Conclusion:

  • The T3500 + W3520 can support 24GB, but only if all modules are fully compatible.

  • Dell workstations are picky about RAM specs — BIOS update and testing configurations should be your first steps.

  • Consider switching to ECC Registered RAM if issues persist — it’s better supported in full-slot configs.

I hope help, feel free to ask of you have more questions.

(edited)

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