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Comment by wtallis | Hacker News Reader

> Another intriguing aspect is the separate CPU and GPU design. If true, this essentially means M5 will not use a unified memory architecture (UMA) shared between the CPU and the GPU.

This does not follow. Intel is shipping unified memory processors with CPU cores and GPU cores on separate chiplets but still sharing the same memory controller (on a third chiplet, for Meteor Lake and Arrow Lake). AMD is about to launch Strix Halo, a high-end mobile processor that is rumored to consist of one or two CPU chiplets and an IO die with a big GPU and 256-bit memory controller.

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Agree. Here is an article on SoIC from Anandtech [1].

Edit: [2] The tweet doesn't even mention about UMA. The interpretation is entirely made up by Notebookcheck, I feel like I am reading WCCFtech again making stuff up.

I am just thinking if this allow Apple to do something crazy like 1024bit LPDDR5x or HBM3e memory solution.

[1] https://www.anandtech.com/show/21414/tsmcs-3d-stacked-soic-p...

[2] https://x.com/mingchikuo/status/1871185666362745227?ref_src=...

Plus Apple themselves are already kind of doing it with the M Ultras - those are two chiplets glued together, each of which is only connected to half of the systems memory directly, but it still behaves like unified memory even though half of the memory traffic has to be routed via the other chiplet.

And in the datacenter space, AMD has taken things even further with the MI300A:

> Twenty-four x86-architecture ‘Zen 4’ cores in three chiplets

> Six accelerated compute dies (XCDs) with 38 compute units (CUs), each with 32 KB of L1 cache, 4 MB L2 cache shared across CUs, and 256 MB AMD Infinity Cache™ shared between XCDs and CPUs

> 128 GB of HBM3 memory shared coherently between CPUs and GPUs with 5.3 TB/s on-package peak throughput

Indeed. Very similar to the grace + hopper, grace + dual hopper, and grace + dual blackwell.

Maybe Apple has figured out something better than a unified memory architecture.

It's hard to rule out their ability to create silicon that is a step change.

I wasn't really trying to comment on what Apple could or could not pull off. Just pointing out that Notebookcheck seems to be misunderstanding what they're reporting on from Ming-chi Kuo, and the headline itself seems to be something Notebookcheck made up rather than something from Kuo's rumors. So this whole thread is even more baseless than it appears at first glance, but it would still be interesting to have an informed discussion about the pros and cons of unified memory for consumer SoCs, and alternatives.

They didn't even figure out unified memory - even original xbox (20+ years ago) had that.

And SGI O2 30 years ago.

Great reminder. I should have been clearer that I meant in the current context the note was being made about Intel and AMD working on things that apple's not.

Nvidia Jetson are all unified memory as are the raspberry pis.

CHIP memory

I think the Apple II frame buffer was in a unified system memory.

Ha ha, right! And with interlaced rows, 7 pixels per byte, and a cockamamie color generation scheme, it had a hardware "graphics decelerator".

And yet it is legendary for running all sorts of great games (Ultima, Bard's Tale, Wizardry, Castle Wolfenstein, Robotron, Prince of Persia, Maniac Mansion, Choplifter, Lode Runner, and many, many others.)

I still want to try last year's Wizardry remake – which actually emulates the original Apple II code (or subsequent NES code), with a capability of displaying the original interface if desired.

UMA is trivial if you have so little RAM that bandwidth doesn't matter.

The original XBox (2001) had 64MB. I think my PC from 1998 had that.

Good point - maybe this is a part of Apple's reasoning, or there's something else architecturally.

For sure, they aren't always the first, but they do seem to scale through some things in their own way. Got me my first fastest cpu laptop with meaningful battery life.

The Amiga had unified memory almost 40 years ago, at least for the first 512K to 2 megabytes (depending on hardware, which Agnus chip, etc.)

The Mac 128k in 1984 had unified memory.

Not to mention nearly every Intel and AMD desktop that has a small iGPU on board, even for the chips not marketed that way.

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