DDR4 on Rocket Lake-S, Gear 1 and Gear 2 mode settings

One of the adjustments that Intel has made within the circuitry of its Gen 11 desktop CPUs, with Rocket Lake-S structure, is the renewal of the reminiscence controller or Northbridge. The a part of the CPU in command of speaking the totally different cores with the RAM. These adjustments have an effect on when selecting DDR4 modules for the PC. We inform you which is the most effective choice.

Gear 1 versus Gear 2 in Rocket Lake-S

Gear 1 Gear 2 Intel

When it involves speaking with RAM, the reminiscence controller in Intel’s Rocket-Lake-S structure CPUs has two totally different modes of operation known as Gear 1 and Gear 2. Gear 1 refers back to the clock pace of reminiscence or MCLK, whereas in Gear 2 mode, that pace is halved.

DDR4 being a kind of DDR reminiscence, the reminiscence clock pace is half that of the Gbps which are stipulated within the reminiscence mannequin, so the reminiscence pace of the DDR4-3600 is 1800 MHz. Regarding the communication of the built-in reminiscence controller, IMC, with the DDR-3600 in Gear 1 mode it’s 1800 MHz and in Gear 2 mode it’s 900 MHz.

The cause why that is achieved is none apart from growing the reminiscence interface clock pace will increase power consumption, so slicing its clock pace can assist greater pace RAM. Another cause is that as we enhance the bandwidth of a reminiscence with its processor, its latency additionally will increase.

CPUs in contrast to GPUs shouldn’t have inside mechanisms to masks latency and RAM with elevated latency attributable to elevated bandwidth is counterproductive in efficiency. With Gear 2 mode, Intel sacrifices bandwidth, however retains latency low and thereby maintains CPU instruction efficiency.

BCLK and QCLK on Intel Gen 11

Rocket Lake Reverso

Now that we all know the variations between each modes, it’s essential to know once we ought to activate Gear 1 mode or Gear 2 mode on the processor. Since it has been proven that the Gear 2 mode at sure clock speeds isn’t solely the one approach that the CPU helps them, however in sure settings the Gear 2 mode offers higher efficiency than the Gear 1 mode. Access by way of Gear 2 works with decrease instruction latencies.

The Rocket Lake-S onboard reminiscence controller works with the next settings:

  • BCLK: Base clock pace of the IMC, this may be 100 MHz (100 x 1) or 133 MHz (100 x 1.33) in Gear 1 mode, whereas in Gear 2 mode it’s 50 MHz (50 x 1) zero of 66.67 MHz (50 x 1.33).
  • QCLK: The clock pace multiplier, in Gear 1 mode can go from x 6 x 27. While in Gear 2 it may go as much as x 63.
  • MCLK: As we have now stated earlier than it’s the reminiscence clock pace.

The formulation to know each the BCLK and the QCLK to succeed in a particular MCLK is the next:


The cause for dividing it by 2 is that we’re speaking a couple of DDR reminiscence, to make it extra accessible we have now determined to get rid of the division, since if we wish to know if a DDR4-2400 reminiscence goes to be appropriate with Rocket Lake-S we simply should make it possible for BCLK * QCLK of a results of 2400.

DDR4 not supported by Rocket Lake-S


From the knowledge defined above we are able to know which DDR4 reminiscence is appropriate with Rocket Lake-S, which BCLK can be utilized and which QCLK multiplier have to be positioned on the BMI within the BIOS of our PC. That is why we have now determined to make two tables, one to be able to know how you can configure the BCLK and the QCLK in Gear 1 modes, the opposite in Gear 2 mode.

The varieties of reminiscence supported in Gear 1 mode might be seen within the following desk:

Rocket Lake Gear 1

As you’ll be able to see in Gear 1 mode, it’s attainable to attach a DDR4-3600 reminiscence by modifying the BCLK to 100 MHz x 1.33 mode, which is greater than the DDR4-3200 as the utmost clock pace that Intel ensures that its Gen CPUs. 11 assist. Which is nice information. As for the DDR4-2800, it isn’t supported with the BCLK in 100 MHz x 1 mode, and requires the 100 MHz x 1.33 mode. Why have we marked it in orange? By the very fact in case you are fortunate you might get one of many Rocket Lake-S with a totally practical multiplier x 28.

As for Gear 2 mode, the desk is as follows:

Rocket Lake-S Speeds RAM Gear 2

In Gear 2 mode the DDR4-4200 is the kind of DDR4 with the best pace supported, however for this it’s essential to activate the BCLK at 50 MHz x 1.33 mode. If we do not we might be restricted to DDR4-3100. Since Gear 2 mode has decrease latencies than Gear 1 mode, we suggest utilizing it. Not solely to have the ability to use reminiscence past DDR4-3200, which is the quickest kind of reminiscence formally supported, but additionally attributable to the truth that the Gear 2 has a better efficiency.

How do I modify the BCLK and QCLK on Rocket Lake-S?

Rocket Lake S BIOS

It may be very easy, you solely should do it within the RAM, many BIOS adapt the pace of the BCLK immediately with out additional issues. Others on the opposite hand will make it’s a must to modify the BCLK and the QCLK manually. In any case, it’s essential to not overlook that in the event you replace the DDR4 reminiscence to your PC with Rocket Lake-S then it’s essential to make the corresponding adjustments within the BIOS to activate a Gear or one other In Rocket Lake-S.