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Hector Martin has a different analysis: This article talks about TB4 vs USB4 but that's a red herring. This has nothing to do with USB4 and Intel U
by mort96 3y ago
Hector Martin has a different analysis:
This article talks about TB4 vs USB4 but that's a
red herring. This has nothing to do with USB4 and
Intel USB4 compliant controllers have the same problem.
The real reason Apple Silicon is faster is simple:
Intel Thunderbolt controllers are *external* and
bottlenecked on a PCIe 3.0 x4 link to the host,
while Apple Silicon *embeds* the controllers right
into the SoC, so there is no physical PCIe link
anywhere. They connect directly to the much faster
SoC fabric, so have no such bottleneck.
I can't say whether he's right or not, but it sounds plausible.
- smith7018 3y agoI'd guess he's right. No one outside of Apple knows more about the inner-workings of the M series than Hector. For those that don't know, he's the main contributor and lead of Asahi Linux.
- toast0 3y agoI think it's reasonable to say a PCIe 3.0 x4 attached thunderbolt controller is bottlenecked by the host attachment; but that doesn't much matter if you're using PCIe 3.0 x4 mode (+/- interleaved display port). And it's also not limiting if you're in USB3 mode. There's only a real issue with capacity if you're using USB4, so I don't see how it's a red herring. Also, I've just read that Thunderbolt 3 has a hard reservation of 18 Gbps for display port data, limiting other data to 22 Gbps, so comparing TB3 to TB4 in pci-e mode will have that caveat as well.
- jakobson14 3y agoinside the TB link there's no such thing as "3.0" or "x4" hector goes over this as well, but basically you've replaced all the lower (physical) layers of PCIe's networking stack. intel like to pretend that thunderbolt and USB4 just tunnel actual PCIe links unchanged (as if they're emulating everything down the PCIe lanes and PHYs), but they don't. PCIe over thunderbolt can run at whatever speed you please, limited only by the throughput of TB and the overhead of the remaining layers of the PCIe stack.
- c_o_n_v_e_x 3y agoI dont know the specifics of the Intel CPUs in Mac machines, but I do know that some Intel core series CPUs come with TB baked into the CPU/SoC. That being said, the comment you've quoted is plausible.