Comment by ralferoo | Hacker News Reader

Comment by ralferoo | Hacker News Reader

I wonder if we'll eventually start seeing a trend for chips to shrink in size.

The existing Ampere chips are already massive (see previous STH videos etc), and most of that is because usually each time they double the number of cores, they usually double the number of memory lanes and IO lanes like PCI etc. But that's squashing ever more heat into a tiny (well, not so tiny with these chips) space.

I'm sure there are some good use cases where you might need that many cores on a single chip, like if there are lots of cache dependencies between all the threads, but I suspect the majority of these chips will end up carved up into smaller VMs and it seems to me that a multi-chip solution is probably more optimal for cooling and air flow.

I guess the counter argument is that chips designed using chiplets could still have a reasonable amount of space between each chiplet on the chip to allow each a greater cooling surface area and presenting one flat metal surface for cooling might perform better than several chips that potentially don't lie exactly co-planar.

At some point, with the current parallel buses, it'll become prohibitive to add more memory bandwidth to a socket. IBM did a lot of interesting things with OMI in their POWER 9 and 10 chips. These serial buses can reduce the pin count substantially.

https://www.servethehome.com/microchip-smc-1000-for-the-seri...

I think we already have that no?

BIG.little with ARM, efficiency cores with Apple, 4C/5C cores from AMD. IF you want more cores, but want to do it efficiency, we have that tech now.

AMD is building out full 4C/5C-based CPUs where everything is efficiency cores, but it gives them more overall cores.

That's not quite what I meant, because these are still just single chip machines.

I was specifically thinking of data centre use where more cores are obviously desirable, and in previous generations multi-chip designs were common e.g. dual-Xenon all the way up to I think quad-Xenon motherboards.

With the rise in core counts recently, most designs have gone back to single-CPU motherboards, but I wonder if we'll decide that 64, 128 or whatever cores per chip is enough, and just have more chips on a motherboard instead. Would give more flexibility for upgrades or replacing faulty CPUs, as well as probably being cheaper to make and easier to keep cool.

We can already do multiple 40GB/s interconnects from on-chip to outside the PC using PCIe/USB-C 3.2, so that kind of fast bus between separate chips on the same motherboard should be achievable for when you actually need cache sharing, and I suspect that with appropriate core-affinity settings, most jobs don't require all that much shared cache access.

You should try looking at any of AMD's server CPUs from the past four generations. They've been making chiplets of 8-16 CPU cores, with several chiplets per package to get much higher core counts than Intel, while still also supporting multiple CPU sockets.

> but I suspect the majority of these chips will end up carved up into smaller VMs

As someone who works with BSD Jails and preferably (though not as often) illumos Unix Zones, I look down my nose at those who would run VMs on these chips.

My org's competitors should go ahead and use VMs.

Reply on news.ycombinator.com