Panther Lake's iGPU is basically an Arc A770 jammed into a mobile chip

After Intel's breakdown of the Xe3 architecture I tested a Panther Lake laptop and found the iGPU is very good. On paper that should be a given: the Arc B390 packs 1536 shaders, 16 MB of L2 cache and a 2.5 GHz boost clock, making it far more potent than most integrated GPUs.

I used Nemez's GPUPerfTest, added to Chips and Cheese's benchmarking suite, to compare the B390 against a couple of other mobile chips and the Alchemist-powered Arc A770. Intel has largely consolidated what worked and shored up weak areas, so Xe3 often feels like a nicely vamped-up Xe rather than a radical redesign.

Microbenchmarks explain why. In fused multiply-add throughput the B390 keeps the Arc A770 in its sights despite having far fewer shaders. Cache and memory tests show impressive internal bandwidth and a wide internal data bus — the B390 pulled roughly 6 TB/s from L1 — while the 4096-shader A770 still leads on raw pipeline count.

panther lake, igpu, arc a770, arc b390, xe3, intel, shaders, l2 cache, gpuperftest, internal bandwidth