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  • #10109 S_x96x_S addikt
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    Zen vs. Lion Cove

    ----

    "Intel’s Lion Cove P-Core and Gaming Workloads"
    https://chipsandcheese.com/p/intels-lion-cove-p-core-and-gaming

    """
    Compared to Zen 4, Lion Cove suffers harder with backend memory latency, but far less from frontend latency. Part of this can be explained by Zen 4’s stronger data-side memory subsystem. The AMD Ryzen 9 7950X3D I previously tested on has 96 MB of L3 cache on the first die, and has lower L3 latency than Lion Cove in Intel’s Arrow Lake platform. Beyond L3, AMD achieves better load-to-use latency even with slower DDR5-5600 36-36-36-89 memory. Intel’s interconnect became more complex when they shifted to a chiplet setup, and there’s clearly some work to be done.

    Lion Cove gets a lot of stuff right as well, because the core’s frontend is quite strong. The larger BTB and larger instruction cache compared to Zen 4 seem to do a good job of keeping code fetches off slower caches. Lion Cove’s large L2 gets credit too. It’s not perfect, because the occasional instruction-side L2 miss has an average latency in the hundreds of cycles range. But Intel’s frontend improvements do pay off.

    Even though Intel and AMD have different relative strengths, a constant factor is that games are difficult, low IPC workloads. They have large data-side footprints with poor access locality. Instruction-side accesses are difficult too, though not to the same extent because modern branch predictors can mostly keep up. Both factors together mean many pipeline slots go unused. Building a wider core brings little benefit because getting through instructions isn’t the problem. Rather, the challenge is in dealing with long stalls as the core waits for data or instructions to arrive from lower level caches or DRAM. Intel’s new L1.5 likely has limited impact as well. It does convert some already fast L2 hits into even faster accesses, but it doesn’t help with long stalls as the core waits for data from L3 or DRAM.
    """

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