Zen 5 Architecture is the “tock” to Zen 4’s “tick” ▉

Gavin Bonshor, Anantech:

The key features under the hood of the Zen 5 microarchitecture include a dual-pipe fetch, which is coupled with what AMD is calling advanced branch prediction. This is designed to reduce the latency and increase the accuracy and throughput. Enhanced instruction cache latency and bandwidth optimizations further the flow of data and the speed of the data processing without sacrificing accuracy.

The Zen 5 integer execution capabilities have been upgraded over Zen 4, with Zen 5 featuring an 8-wide dispatch/retire system. Part of the overhaul under the hood for Zen 5 includes six Arithmetic Logic Units (ALUs) and three multipliers, which are controlled through an ALU scheduler, and AMD is claiming Zen 5 uses a larger execution window. These improvements should theoretically be better with more complex computational workloads.

Other key enhancements that Zen 5 comes with include more data bandwidth than Zen 4, with a 48 KB 12-way L1 data cache that can cater to a 4-cycle load. AMD has doubled the maximum bandwidth available to the L1 cache, and the Floating-Point Unit has been doubled over Zen 4. AMD also claims it has improved the data prefetcher, which ensures faster and more reliable data access and processing.

More pipelines means more instructions. More instructions means more gets done faster.

For CPUs, cache is king. Having wider pipelines allows it to do more tasks or just simply have more data ready without having to reach out to system memory. While it may not seem like a bog deal, in computers, reaching out to system memory is costly in terms of time. Time that may not seem that much to us but is forever in computer terms. It’s most noticeable to a user when, say, a game or application stalls or takes a while to start.

Something else AMD is claiming is that they have improved the overall thermal resistance of the CPUs and managed to reduce the operating temperatures with the Ryzen 9000 processors (Zen 5) over the previous Ryzen 7000 (Zen 4) series. In terms of thermal resistance, AMD claims a 15% improvement over Ryzen 7000. At the same time, they also claim they have managed to reduce operating temperatures by 7°C when operating at a like-for-like TDP. Unfortunately, when asked at the Tech Day in LA last week, AMD wouldn’t divulge how they managed these improvements, but that’s not a surprise.

Despite operating with a lower TDP, comparing performance like-for-like, the Zen 5 cores perform up to 22% higher on the Ryzen 9 9950X vs. the Ryzen 9 7950X, while even the Ryzen 9 9900X with a 120 W TDP against the previous Ryzen 9 7900X (170 W), performs up to 16% higher. One thing AMD’s Zen microarchitecture is known for is its power efficiency, as well as how much performance is retained when operating at a lower wattage than TDP. We did some power scaling testing with the Ryzen 9 7950X against the Intel Core i9-13900K, and we were impressed with how much performance the Zen 4 cores managed to retain despite operating at much lower than stock in relation to TDP.

This is really great to hear. One of my concerns was the trend, even with AMD, of higher and higher thermals due to more and more power draw in an effort to reach higher clock speeds. While speeds are up, the TDP is either the same or lower than Zen 4. This is probably how AMD is making their efficiency clam. Lower temps mean the chip can work longer at the same temps which means it can maintain it’s higher clock speeds in more burdensome workloads. Like gaming or compiling code.

AMD has really taken on Intel’s old “tick tock” cycle. Release a CPU that has some pretty good gains one cycle and then refine that CPU the next cycle. That’s exactly what they did here with Zen 4 to Zen 5.

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