Friday, May 10th 2019
AMD Ryzen 3000 "Zen 2" a Memory OC Beast, DDR4-5000 Possible
AMD's 3rd generation Ryzen (3000-series) processors will overcome a vast number of memory limitations faced by older Ryzen chips. With Zen 2, the company decided to separate the memory controller from the CPU cores into a separate chip, called "IO die". Our resident Ryzen memory guru Yuri "1usmus" Bubliy, author of DRAM Calculator for Ryzen, found technical info that confirms just how much progress AMD has been making.
The third generation Ryzen processors will be able to match their Intel counterparts when it comes to memory overclocking. In the Zen 2 BIOS, the memory frequency options go all the way up to "DDR4-5000", which is a huge increase over the first Ryzens. The DRAM clock is still linked to the Infinity Fabric (IF) clock domain, which means at DDR4-5000, Infinity Fabric would tick at 5000 MHz DDR, too. Since that rate is out of reach for IF, AMD has decided to add a new 1/2 divider mode for their on-chip bus. When enabled, it will run Infinity Fabric at half the DRAM actual clock (eg: 1250 MHz for DDR4-5000).
This could turn into an additional selling point for AMD X570 chipset motherboards, as they'll have a memory frequency headroom advantage over boards based on older chipsets as their BIOS will include not just the increased memory clock limit, but also the divider mode. Of course this doesn't mean that you can just magically overclock any memory kit to these 5 GHz speeds - it's probable that only the best of the best modules will be able to get close to these speeds.
1usmus also discovered that the platform adds a SoC OC mode and VDDG voltage control. We've heard from several sources that AMD invested heavily in improving memory compatibility, especially in the wake of Samsung discontinuing its B-die DRAM chips.
The third generation Ryzen processors will be able to match their Intel counterparts when it comes to memory overclocking. In the Zen 2 BIOS, the memory frequency options go all the way up to "DDR4-5000", which is a huge increase over the first Ryzens. The DRAM clock is still linked to the Infinity Fabric (IF) clock domain, which means at DDR4-5000, Infinity Fabric would tick at 5000 MHz DDR, too. Since that rate is out of reach for IF, AMD has decided to add a new 1/2 divider mode for their on-chip bus. When enabled, it will run Infinity Fabric at half the DRAM actual clock (eg: 1250 MHz for DDR4-5000).
1usmus also discovered that the platform adds a SoC OC mode and VDDG voltage control. We've heard from several sources that AMD invested heavily in improving memory compatibility, especially in the wake of Samsung discontinuing its B-die DRAM chips.
112 Comments on AMD Ryzen 3000 "Zen 2" a Memory OC Beast, DDR4-5000 Possible
Maybe someone else will jump in and lend a hand, but I actually have no time to waste right now.
Can we accept Ryzen 3000 for what it once it launches or do we have to read clickbait "news" like this every day just to see for the 1000th time the real product never meets expecations if they're crazy high.
www.techpowerup.com/forums/threads/amd-ryzen-3000-zen-2-a-memory-oc-beast-ddr4-5000-possible.255405/#post-4045685
memory beast ? come on.
the title doesn't even match the contents for god's sake as it says in order to reach such speeds you need 1/2 IF divider.
But take a i9 14 core, remove two sticks and do dual channel, surprise!
Doesn't affect it that much at all!
Zens major limitation is latency more than bandwidth.
But surprise! Frequency decreases latency.
So yeah, to some extent bandwidth but I feel the latency is really what they are after.
Ontopic: I think with a half divider of IF and 2500Mhz memory speeds, you can still pack more bandwidth then ever and still get better scores. I dont think it's a useless feature but one beneficial.
I know I'm a unique usecase with full DIMM population with dual ranked modules, but I was a little surprised how weak Intel's memory controller is in this situation.
My motherboard is an Extreme Zenith paired with a Threadripper 1950X overclock at 4.0 GHz with 1.37-1.39 using the compensating voltage mode.
Before I was using 8X4 GB of Corsair Dominator, you can not make them work at their advertised speed, work at the advertising speed of 3000 MHz CL15-17-17-35, could only make then work at 2800 Mhz
4 sticks were Hynix chips and the other Micron.
If this will become true, it will actually be very good.
I mean, you get very fast memory and have to push it through a thin straw of halved IF to CPU cores. Sure if IF at 1250Mhz is significantly faster than memory at 5000 then it is not a big issue but if not - you loose that gained speed from increasing memory frequency. The more important thing when running IF at half speed would be timings. Whatever you gain from better timings in memory modules you loose much more in IF lagging behind - memory chip optimisation would gain us 10-20ns while IF running at half speed would loose us a 50ns easily? Consider that without any optimisations we get over 100ns for 2133 memory and corresponding 1066 IF speed and around 80 for 3200 memory and 1600 IF link - that is 20ns lag for 500Mhz of IF link speed. Sure increasing IF link speed would give us decreasingly smaller gains but still... going from 4000 memory with IF at 2000 to IF at 1000 would "kill the performance dead" ;)
It's good only for breaking speed records.
Now, if AMD would be to introduce 2x IF multiplier, that would enable use to lower delays introduced by slow IF link...
Consider somewhat slow memory at 3000 that results in IF running at 1500 and apply 2x to that to get IF running at 3000? IF link with delays on the order of 25ns... and even with low quality memory running at 2133 or 2400 we would get IF running at 2133 and 2400. It would eliminate the problem with IF bus concurrency when communicating with memory controller and PCIEx (GPUs) that can happen in current scenarios. All that, if IF would be able to run at that speeds.... but considering that some memory kits are able to run 3733 on ZEN+ and that means 1866 for IF it is not really far from 2133...
One can dream of course.
Edit: reading up on IF speeds in current Zen, I assume AMD doubled the width of IF links from CCX to RAM, otherwise the divider would also limit RAM bandwidth.This is the entire problem and reason for introducing the divider - IF cannot run at that high a clock. There is hope that AMD has improved IF in Zen2 but we will ahve to wait and see what approach they have taken with it.