Panther Lake Arc B390 iGPU on SO-DIMM memory performs worse compared to using LPDDR5X, 16% slower in 3DMark

The Arc B390 is Intel's latest and fastest iGPU to date; however, one quirk of the GPU is that it requires high-speed LPDDR5X to reach its advertised performance. YouTuber ETA Prime tested the Arc B390 with slower DDR5-5600 SO-DIMM memory to see what the performance repercussions were and saw noteworthy performance losses compared to running the same iGPU with much speedier LPDDR5X memory.

The system ETA Prime used to test was an ASRock NUC BOX-358H featuring a Core Ultra X7 358H with 16 cores and an Arc B390 iGPU. The small form factor PC features two SO-DIMM DDR5 slots rather than embedded LPDDR5X, with support for up to 128GB of memory at up to 7200MT/s. But for testing, the YouTuber opted to put in two 16GB DDR5 sticks running at 5600MT/s. The YouTuber put the system through several benchmarks but only compared the Panther Lake system to an identical system running LPDDR5X memory in one benchmark, 3DMark Time Spy.

In 3DMark Time Spy, the Core Ultra X7 358H with DDR5-5600 memory achieved 6,221 points; by contrast, the same CPU with speedier 8335MT/s memory achieved 7,345 points, representing an 18% advantage in performance. In Forza Horizon 6, the NUC achieved roughly 73 FPS average at 1080p high settings, around 65 FPS average in Spider-Man 2, at 1080p medium settings using XeSS in balanced mode. In Cyberpunk 2077 at 1440p high settings, the game hit around 85 FPS average using XeSS frame gen set to a 3x multiplier.

The YouTuber unfortunately did not provide any gaming comparisons to a B390 equivalent system paired with LPDDR5X memory, but previous footage from the YouTuber's channel shows the same Arc B390 and 358H CPU in a laptop achieving very similar frame rates in Spider-Man 2 but running at a substantially higher 2880x1800 resolution and using high settings with XeSS balanced mode.

ETA Prime's findings confirm that Intel's Arc B390 is highly memory sensitive and demands the fastest system memory to wring the most amount of performance from the chip. Memory speed is so critical that Intel stops displaying the Arc B390 by its namesake in Windows if you pair the iGPU with slower memory, instead displaying "Intel Graphics". It seems a bit harsh to not display the iGPU's name in Windows, but Intel's logic behind this idea is understandable due to the various memory configurations that work with its Panther Lake CPUs. DDR5-5600 is not even the slowest DDR5 RAM you can buy; speed bins as low as DDR5-4800 exist as well.

For the uninitiated, the Arc B390 is the latest flagship integrated graphics chip to come out of Intel, and is built on its latest Xe3 GPU architecture. The GPU comes with 12 Xe cores, clocked at up to 2.3 GHz, and has a base power rating of 25 watts alone (not counting CPU power). The B390 is a massive leap over Intel's previous fastest iGPU found in its Lunar Lake CPUs, with advertised performance matching entry-level discrete GPUs such as NVIDIA's RTX 4050.