Actual RAM limit of Thinkpad T510

Question

What's the actual RAM limit for a Thinkpad T510 CTO 4384 with i5-520M CPU?

I've often seen 16 GB working in Thinkpads even when manuals and Crucial state 8 GB, so asking before I upgrade. For example, here Crucial says the max RAM for the T420 with i5-2520M I'm using is 8GB, but 16GB runs AOK with full utilization.

I ran inxi -Fxmz in Linux, with the results:

Memory:
  RAM: total: 3.70 GiB used: 812.6 MiB (21.4%)
  Array-1: capacity: 8 GiB slots: 2 EC: None max-module-size: 4 GiB
  Device-1: DIMM 1 size: 2 GiB speed: 1066 MT/s type: DDR3
  Device-2: DIMM 2 size: 2 GiB speed: 1066 MT/s type: DDR3

Update: There are 4 slots for modules as per pages 73 & 79 of the manual but when I opened the covers, there are only 2 sockets for DIMMs; there's space for another socket but the socket ain't there, dagnabit. Oh, bother.

Answer 1

The limit is 8GB, tested and tried by garage_maxedout[1] (see video description and highlighted comment) and confirmed by fellow owners[2][3].

You can tell from other disassembly videos and comments that T510 has 2 slots while W510 has 4 slots, so the manual is misleading.

Answer 2

The maximum memory a processor supports depends on the maximum DIMM size the processor supports. Typically current processors will support two of those DIMMs on each memory channel, and have two memory channels.

That means that the maximum memory assumes that you can fit 4 DIMMs in your PC.

The main difference between laptops and normal machines is that laptops almost always have only one single DIMM slot per memory channel, while most desktops have two.

As a result laptops often support only half the amount of memory that the processor could actually allow.

Intel claims your i5-520 can only support a total of 8.3GB, which is a slightly odd number.

Answer 3

Your Hardware Maintenance Manual only specifies two DIMM slots for memory. In addition, on page 151 for the list of parts, only memory sticks of up to 4GB are listed.

For a second opinion, the RAM manufacture Crucial in its Lenovo ThinkPad T510 Series page only lists RAM up to 2x4GB. Crucial is pretty exact in its results, but for an on-spot test you could run the Crucial System Scanner which will scan your actual hardware and give a very accurate report.

The conclusion is that your computer is limited to 8GB total RAM, both because of its motherboard design and also that of the CPU (see answer by Mokubai).