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Comment by initplus | Hacker News Reader

The missing L3 cache is interesting, I can only assume that it's another sacrifice made for power optimisation. Maybe their perf metrics showed disabling L3 provided a worthwhile power/perf tradeoff?

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It seems like a test artifact on the latency test.

> L3 issues seem to be gone with a bandwidth test, with similar results using Windows or Linux. We see over 200 GB/s of L3 bandwidth with an all-thread load.

Somethings weird. There's definitely an L3 and it definitely works but not as predictably as most cores.

Maybe cost too. Custom 7nm silicone aint cheap and the steamdeck is quite an affordable product considering Vlave don't have access to the same economies of scale that Sony, Nintendo or Microsoft do.

The L3 cache appears again in Windows, so it's clearly there physically on the die. But under the default performance tuning of the deck seems like it's not really being used. Possibly they are turning L3 off/down at runtime?

Big guess here (I mostly know CPU design from what EE I gleaned from college) but my guess is that the L3 is shared per CCX, which probably makes it harder to properly power down/up when only one core is in use.

Steam Deck only has a Single CCX.

isn't that expected for a 4 core?

Yep.

Maybe AMD took on a bit of the costs for developing the Steam Deck APU so that they can sell it to other users as well like NVIDIA did with the Tegra chip.

AFAIK nothing else uses the Steam Deck APU despite there being several PC handheld manufacturers. All the others go with standard laptop chips for better or worse.

Although I wonder how much exclusivity you get anyways with how remarkably similar the PS4/Xbox One and PS5/XSX designs are.

> considering Vlave don't have access to the same economies of scale that Sony, Nintendo or Microsoft do.

Don't underestimate them, Valve is similar in revenue to Microsoft Gaming Division, so I think they can afford selling hardware at a loss.

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