News Alder Lake Tested With DDR5-6400 Memory, Reveals Unexpected High Latency

InvalidError

Titan
Moderator
In other words: business as usual.

Historically, the fastest memory on a new standard comes at the expense of increased latency and you are better off using reasonably fast low-latency previous-gen stuff for most workloads. It has always been that way as far as I can remember so I would never buy first-gen memory or first-gen CPUs on new memory, too many things need to get tweaked on both sides before next-gen memory gets a mostly clean benchmark suite sweep for a palatable markup over premium but still cheaper previous-gen stuff.
 

wifiburger

Honorable
Feb 21, 2016
442
9
10,815
9
horrible latency, not sure why we need 80Gb/s+ for bandwidth on consumer chips
I would bet not even 16core will make use of it

If that was the case, we would of got 3 or 4 channel DDR4 by now with Ryzen cpus

If DDR5 needs Gear4 , no amount of speed will recover that crazy latency.

Usually Intel is considered the best when it comes to memory controllers ... wonder what AMD latency will be lol
 

InvalidError

Titan
Moderator
horrible latency, not sure why we need 80Gb/s+ for bandwidth on consumer chips
I would bet not even 16core will make use of it
16 cores is getting bottlenecked by dual-channel DDR4 in many workloads, so DDR5 will be very much necessary for consumer CPUs to scale beyond that. More system memory bandwidth will also be great for future IGPs and the latency of affordable DDR5 should be considerably better by then, along with the overall performance of 2nd/3rd-gen DDR5 controllers.
 
Reactions: Makaveli

JWNoctis

Upstanding
Jun 9, 2021
338
73
290
5
I'd expect much larger L3 cache and/or some exotic kind of L4 cache going mainstream, while DDR5 lasts. What's the typical latency of an on-module HBM2 stack?

Even then, there are still those workloads where no reasonable amount of cache is going to help. Not that there are many in client space, though.
 

InvalidError

Titan
Moderator
Simply put: exercise patience, don't early adopt, except if circumstances force you to do so - and even then, Ryzen is an alternative...
Zen 4 will be on DDR5 too and I'd expect it to have similar issues with DDR5 until lower latency DDR5 equivalent to today's 3200-16 bargain basement stuff becomes readily available.

Keep in mind that 6400-40 is 25% worse CAS latency than today's relatively cheap and plentiful 3200-16.
 
Reactions: Makaveli

Phaaze88

Titan
Ambassador
Zen 4 will be on DDR5 too and I'd expect it to have similar issues with DDR5 until lower latency DDR5 equivalent to today's 3200-16 bargain basement stuff becomes readily available.

Keep in mind that 6400-40 is 25% worse CAS latency than today's relatively cheap and plentiful 3200-16.
Well... never mind.
Just wait, except if forced to do so.
 

thestryker

Honorable
Apr 19, 2016
7
3
10,515
0
One would think this is actually completely expected given the increased latency in DDR5. I'd be shocked if gear 4 was necessary to run 6400 as that'd be the same as running RKL gear 2 at 3200 and would imply a major reduction in the quality of the memory controller. Now if those tests were done with 6400 and gear 2 then it might be something worth note. Gear 4 shouldn't really enter into play until we're in the 8000 range, and even then I'd bet the increased latency wouldn't be worth it unless you specifically needed the bandwidth.
 
In other words: business as usual.

Historically, the fastest memory on a new standard comes at the expense of increased latency and you are better off using reasonably fast low-latency previous-gen stuff for most workloads. It has always been that way as far as I can remember so I would never buy first-gen memory or first-gen CPUs on new memory, too many things need to get tweaked on both sides before next-gen memory gets a mostly clean benchmark suite sweep for a palatable markup over premium but still cheaper previous-gen stuff.
95 ns seems a lot, previous migrations were in their 80's, in 3->4 and then they fell each iteration. Still ddr2 -3 and 3-4 were less drastic changes, so I assume they were a lot easier to make.

I don't find it wired that young product vs mature one have such differences. It's literally the first kit you could get at that speed, I am sure they relaxed the screws a lot, just for the sake of getting enough of the sticks out there. Being first on the market means more than starting with good product when all early adopters are already riding someone else product.
I am quite sure 6M from start, there will be "enthusiast kit" available with ~20% lower latency.

I might be one of the early adopters, as extra ram AND performance gains will be enough for me. I will be moving mobile workstation from 8'th intel, so it's still a lot more than I have in this frying pan.
 

InvalidError

Titan
Moderator
It will be interesting to see the assorted 1080P gaming benchmarks with assorted DDR5 varieties available at launch...
With DDR5 officially starting at 4400MT/s which should be plenty for CPUs under 16 cores, I predict that the launch sweet spot for most next-gen CPUs will be whatever the lowest effective latency DDR5 will be. And as usual, the cheapest next-gen memory that will consistently beat premium previous-gen will be pricey.

If you don't mind sticking with high-premium DDR4 at the highest frequency that will run 1:1/Gear1, something along the line of 4000-16-19-19 will likely rob DDR5 of many real-world benchmark wins and probably still be cheaper at launch, at the expense of being screwed if you ever need to upgrade RAM later.
 

ASK THE COMMUNITY

TRENDING THREADS