Dell part 30KNJ is a 64GB DDR4 server memory module. It runs at 2666 MT/s, uses 288 pins, and needs 1.2V. It is an LRDIMM with a quad-rank, x4 layout, so the sticker reads 64GB 4Rx4 PC4-2666V-L.

Reading the sticker

• 64GB: the size of the module
• 4Rx4: four ranks of x4 memory chips (Dell sometimes writes 4DRx4)
• PC4-2666V: DDR4 at 2666 MT/s, which moves 21.3 GB/s per module
• L: load-reduced, meaning data buffer chips sit on the module

Why LRDIMM matters

Load-reduced modules let a server hold more memory per channel. The buffer chips hide the load of all those memory chips from the memory controller. The trade is a little extra latency and some added power.

An LRDIMM can't share a server with plain RDIMMs. Pick one type and stay with it. Match the speed too, because the whole system runs at its slowest module or at the CPU limit. Registered ECC memory also won't work in a desktop PC.

How much memory fits

A 64GB module uses one slot, the same as a 32GB module, so it doubles what each slot holds. Dell's own 64GB 4Rx4 LRDIMM at this speed, part A9781930, lists the PowerEdge R740xd, R840, R940, and T640. Check your server's memory guide for the slot layout and speed limits.

Quick answers

Is 30KNJ the same as 030KNJ?

Yes. Dell often prints a leading zero on labels. It is one part.

What does 4Rx4 mean?

More ranks put more memory chips on one module, which raises capacity. Four ranks of x4 chips is how a 64GB module is built.

What does CL19 mean?

It is the CAS latency, the number of clock cycles between a read command and the first data. Lower is quicker at the same speed.

Will it run faster than 2666?

No. The module is rated for 2666 MT/s. A faster CPU won't push it past that.

30KNJ specifications