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I've been asked questions related to the memory controller bandwidth on the past about other CPUs. Its a broad question with a bunch of answers depending on the initial question. So I figured I would try to tackle Alder Lake and DDR5. What is the sweet spot going to be and why?
It all comes down to the memory controller and what the limits are per CPU as they are not all the same. From my testing it seems Gear 1 taps out around 3600-4133 MT/s. After a BIOS update for the ASUS Z690 TUF I was able to get 4133 stable. It took some voltage adjustments to the SA and TX, but it passed the tests.
With this knowledge it was time to switch over to Gear 2. This will run the memory controller at half the speed of the memory frequency. So if 4000 MT/s is stale at Gear 1, that would be 2000 MHz for the controller. Gear 2 would mean the memory is still running at 2000 MHz, but the controller is now at 1000 MHz. It is easy to see that switching over to Gear 2 for higher frequency memory is not always beneficial. You must now run DDR4-8000 to saturate that memory controller fully.
With DDR5 I cannot get Gear 1 to work at all, but the same principal applies. Gear 2 is the new Gear 1 and Gear 4 is now Gear 2 for DDR5. If the memory controller limit is still 1600-2000 MHz regardless of the type of memory being used. We can roughly say the limit of Gear 2 is 6400-8000 MT/s. Above this Gear 4 would need to be applied. Maybe in a few years we will have 10000 MT/s memory kits. Not anytime soon though.
I believe the sweet spot in the future will be around 6400 MT/s. The bad binned controllers and MBs could still run this. While the best may tap out around 7000 MT/s. Since no retail kit is available above DDR5-7000, it will be a while until we find out for sure. After all those world-records runs are always with 1 stick and LN2. I do not count that as a good projection. Since no memory kit will be out anytime soon that is 8000+, Gear4 may never be used for Alder Lake outside of world record runs.
I would like to hear people thoughts on this and where I might be wrong on some or all of it. The 2x 32 bit bus for DDR5 may be a factor as well.
It all comes down to the memory controller and what the limits are per CPU as they are not all the same. From my testing it seems Gear 1 taps out around 3600-4133 MT/s. After a BIOS update for the ASUS Z690 TUF I was able to get 4133 stable. It took some voltage adjustments to the SA and TX, but it passed the tests.
With this knowledge it was time to switch over to Gear 2. This will run the memory controller at half the speed of the memory frequency. So if 4000 MT/s is stale at Gear 1, that would be 2000 MHz for the controller. Gear 2 would mean the memory is still running at 2000 MHz, but the controller is now at 1000 MHz. It is easy to see that switching over to Gear 2 for higher frequency memory is not always beneficial. You must now run DDR4-8000 to saturate that memory controller fully.
With DDR5 I cannot get Gear 1 to work at all, but the same principal applies. Gear 2 is the new Gear 1 and Gear 4 is now Gear 2 for DDR5. If the memory controller limit is still 1600-2000 MHz regardless of the type of memory being used. We can roughly say the limit of Gear 2 is 6400-8000 MT/s. Above this Gear 4 would need to be applied. Maybe in a few years we will have 10000 MT/s memory kits. Not anytime soon though.
I believe the sweet spot in the future will be around 6400 MT/s. The bad binned controllers and MBs could still run this. While the best may tap out around 7000 MT/s. Since no retail kit is available above DDR5-7000, it will be a while until we find out for sure. After all those world-records runs are always with 1 stick and LN2. I do not count that as a good projection. Since no memory kit will be out anytime soon that is 8000+, Gear4 may never be used for Alder Lake outside of world record runs.
I would like to hear people thoughts on this and where I might be wrong on some or all of it. The 2x 32 bit bus for DDR5 may be a factor as well.