Ask HN: Why hasn't x86 caught up with Apple M series?

> A big thing is storage. Apple uses extremely fast storage directly attached to the SoC and physically very very close. In contrast, most x86 systems use storage that's socketed (which adds physical signal runtime) and that goes via another chip (southbridge).

Why would PCIe SSDs need to go through a southbridge? The CPU itself provides PCIe lanes that can be used directly.

> That means, unlike Mac devices that can use storage as swap without much practical impact, x86 devices have a serious performance penalty.

Swap is slow on all hardware. No SSD comes close to the speed of RAM - not even Apple's. Latency is also significantly worse when you trigger a page fault and then need to wait for the page to load from disk before the thread can resume execution.

> The CPU itself provides PCIe lanes that can be used directly.

It does, but if you look at the mainboard manuals of computers, usually it's 32 lanes of which 16 go to the GPU slot and 16 to the southbridge, so no storage directly attached to the CPU. Laptops are just as bad.

Intel has always done price segmentation with the number of PCIe lanes exposed to the world.

Threadripper AMD CPUs are a different game, but I'm not aware of anyone, even "gamer" laptops, sticking such a beast into a portable device.

> Latency is also significantly worse when you trigger a page fault and then need to wait for the page to load from disk before the thread can resume execution.

Indeed, but the difference in performance between an 8GB Windows laptop and an 8GB M-series Apple laptop is noticeable, even if all it's running is the base OS and Chrome with a few dozen tabs.

> It does, but if you look at the mainboard manuals of computers, usually it's 32 lanes of which 16 go to the GPU slot and 16 to the southbridge, so no storage directly attached to the CPU. Laptops are just as bad.

Why would the southbridge need a whole 16 lanes? That's 32 GB/s of bandwidth (or 64, if PCIe 5). My (AMD) motherboard has the GPU and two M.2 sockets connected directly to the CPU and it's one of the cheaper ones. No idea about my laptop but I expect it to be similar because it's also AMD. Intel is obviously different here because they're more stingy with PCIe lanes.

There should be no reason for a laptop with only an integrated GPU to dangle storage off the southbridge. They take at most 4 lanes and can work with less.

> Indeed, but the difference in performance between an 8GB Windows laptop and an 8GB M-series Apple laptop is noticeable, even if all it's running is the base OS and Chrome with a few dozen tabs.

Any Windows laptop that comes with 8GB of RAM is going to have a crappy SSD included because those are always built to be cheap, not performant. It could even be a SATA SSD (500MB/s bandwidth max). Most likely they'd come with a processor significantly slower and a decent chance the RAM would also be single channel, too.

> It does, but if you look at the mainboard manuals of computers, usually it's 32 lanes of which 16 go to the GPU slot and 16 to the southbridge, so no storage directly attached to the CPU.

AFAIK that's not the case at least on AMD (not Threadripper, but the mainstream AM5 socket). They have 28 lanes of which 16 go to the GPU slot, 4 go to the southbridge, 4 are dedicated to M.2 NVMe storage, and 4 go to either another PCIe slot or another M.2 NVMe storage. See for a random example this motherboard manual https://download.asrock.com/Manual/B650M-HDVM.2.pdf which has a block diagram on page 8 (page 12 of the PDF).