What AMD’S 64-core ‘Rome’ server CPU tells us about Ryzen 2

Rome fea­tures a ‘chiplet’ de­sign with 7nm-based x86 cores sur­round­ing a 14nm IO chip.

PCWorld (USA) - - News - BY GOR­DON MAH UNG

AMD’S Ryzen 2 con­sumer CPU isn’t com­ing un­til 2019, but we saw hints of what to ex­pect in “Rome,” the 64-core server CPU AMD un­veiled in early Novem­ber. It’s based on a new 7nm Zen 2 core that’s likely to find its way into Ryzen 2 next year. Let’s take a closer look.

Each Rome CPU will fea­ture 64 cores with sym­met­ri­cal multi-thread­ing for 128 threads per socket. The CPU it­self is “rev­o­lu­tion­ary,” AMD said, and is built around eight sep­a­rate 7nm “chiplets” with eight cores each.

The chipsets con­tain no mem­ory con­troller or PCIE, but are in­stead tied to a cen­tral IO chip built on 14nm. The IO chip has 8 chan­nels of DDR4 plus sup­port for PCIE 4.0. The com­pany con­nects each chiplet to the IO

chip via a 2nd-gen­er­a­tion re­duced la­tency In­fin­ity Fabric.

The chiplet isn’t the only new fea­ture. AMD said it re­worked the Zen 2 core to of­fer dou­ble the throughput, in­creased float­ing point per­for­mance, a dou­bled core den­sity and half the en­ergy use per op­er­a­tion of Zen. Com­pared to Zen, AMD said to ex­pect twice the per­for­mance and four times the float­ing point per­for­mance per socket. Just the process im­prove­ments alone would give it a 1.25x per­for­mance bump if the power con­sump­tion were kept the same, the com­pany said.

And yes, it’s fast. AMD showed a pre­pro­duc­tion, air-cooled, non-over­clocked Rome out­per­form­ing a dual-socket Sky­lake SP with 56 cores and 112 threads in the float­ing-point in­ten­sive C-ray bench­mark ( go.pc­world.com/cray).

SO WHAT DOES THAT MEAN FOR RYZEN 2?

What’s not known is how much of the Rome DNA will make it into the con­sumer Ryzen 2 due early next year. At a min­i­mum, we’d ex­pect the same 8-core chiplets to be scaled down for desk­top use. All of the front-end im­prove­ments, float­ing point per­for­mance, and ef­fi­cien­cies of the 7nm process are likely to make it a mean CPU.

“By us­ing the Zen 2 ar­chi­tec­ture and 7nm, on desk­tops,” said an­a­lyst Pat Moor­head of Moor In­sights. “I am ex­pect­ing im­proved raw core per­for­mance with fre­quency and IPC im­prove­ments pos­i­tively im­pact­ing lower

AMD’S lat­est “Rome” CPU fea­tures a ba­sic chiplet de­sign with the 7nm ex­e­cu­tion cores con­nected to a 14nm IO chip via faster In­fin­ity Fabric.

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