Intel's Arc Alchemist and DG1 discrete GPUs are buggy with problems in DDT and PCIe 4.0

Intel Xe sample for developers
Intel DG1 dev kit

Intel is almost ready to take a swing at AMD and Nvidia with its first-gen Arc Alchemist GPUs and the entire lineup recently leaked out courtesy of Intel's own driver. However, tests have suggest there are many teething issues and bugs that must be ironed out before Intel's discrete GPUs are ready to join the arena.

The latest bug was discovered by Twitter user Löschzwerg who has been testing the Intel Xe LP-based DG1 graphics card for a while. The bug pertains to PCIe 4.0 throughput wherein the Gunnir Index V2 DG1 is unable saturate the PCIe 4.0 lanes using 3DMark's PCI Express feature test.

The Index V2 seems to work well on all the previous PCIe interfaces up to the 3.0 standard. But on PCIe 4.0, the card is performing the same as PCIe 3.0 even though it should get around double that score. This indicates either some form of bottleneck or a bug on DG1.

Gunnir DG1 Index v2 3DMark PCIe test

PCIe 4.0

Gunnir DG1 Index v2 3DMark PCIe test

PCIe 3.0

Gunnir DG1 Index v2 3DMark PCIe test

PCIe 2.0

Gunnir DG1 Index v2 3DMark PCIe test

PCIe 1.1

Moving on to Arc Alchemist, which is based on Xe HPG architecture, the successor to Xe LP, the first review for Arc A350M have also shown that Intel's Dynamic Tuning Technology (DTT), a feature similar to AMD's SmartShift technology, is hurting the performance of the Arc GPU. When DTT is turned off there is nearly a doubling of the framerates as can be seen in the images below:

Arc A350M performance comparison with DTT on and off
Arc A350M performance comparison with DTT on and off

The DTT should be fairly easy for Intel to fix if it hasn't already been as it likely only needs some optimization to the power states (P-states). Meanwhile, fixing the PCIe bug might be a bit more difficult as the issue isn't generally such a common one among AMD Radeon or Nvidia GeForce GPUs. However, the bug so far has only been noticed on the older DG1 cards which is rarely on anyone's purchase radar as it was never officially released for the DIY market.

Sources and images: Löschzwerg (Twitter) and BullsLab Benchmarks (YouTube)

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