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Comment by kalleboo | Hacker News Reader

It still has a lot of limitations that matter to many pros - max 16 GB of RAM, max 2 displays (only 1 external for laptops), only enough PCIe lanes to support 2 thunderbolt ports. eGPUs aren't supported either, but hopefully that is a software thing that will be fixed.

It will be very interesting to see what the performance will be of the more "pro" chip that overcomes those limitations that they'd put in the 16" and iMacs

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It’s a first generation chip in a thin-and-light laptop. I suspect all those problems will be fixed as they scale it up. Not to mention their unique position of leverage dedicated acceleration silicon in their software now.

eGPU support will depend on if they have a way to work around the need for a PCIe I/O BAR. Many GPUs require that to initialize and as far as I know no ARM cpus support it since it's a legacy-ish x86 thing. It'll be the same problem that prevents gpu use on raspberry pi 4s still. I bet you can make a controller that'll provide a mapping for that to allow it but that'll mean needing a new enclosure (probably not a huge deal) and new silicon and drivers.

I don't quite get how Apple could claim to be Thunderbolt-compatible with this sort of limitation in hardware, though.

It's not a limitation in hardware. It's a legacy feature of the x86 that isn't supported on ARM.

This could be solved by the GPU engineers by removing the legacy compatibility. "Nobody" boots a modern PC from BIOS anymore

AMD GPUs work just fine with POWER8 hardware so this is certainly solved.

AMD GPUs do not require I/O BARs, and highly doubt Nvidia ones do either. The VBIOS will probably assume it can use it, but most modern cards can be initialized without actually running the VBIOS (because people use them on headless servers, for virtualization, and things like that). The I/O BAR is only required for legacy VGA compatibility, you can ignore it.

max 2 displays (only 1 external for laptops)

I wonder if that includes AirPlay screens, or just wired.

This may work. On a 2014 macbook air, which officially only supports only one external display, I've been able to use two external screens at the same time by sharing one through airplay. However, you're always limited in resolution and latency that way.

I would imagine just wired - it's probably a lack of DisplayPort/HDMI encoders rather than rendering resources.

why would it be only 1 external display? Can you not plug into a thunderbolt dock and use multiple external displays? I do exactly that with my 2012 MacBook Pro.

It's a limitation of the M1 chip apparently

https://appleinsider.com/articles/20/11/11/how-apple-silicon...

That’s merely speculation as to why.

You can use sidecar with an ipad for a second external display.

With some iPads. Not all. I was thinking of using an older iPad for this purpose, but alas. Won't work. Too old.

The embedded GPU doesn't support it

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