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Well, they could put in a memory controller for both DDR5 and HBM on the die, so they would only have one die to tape out.

The Max variant is something they are using in their own datacenters. It would be possible that they would use an HBM solely for themselves, but it would be cheaper overall if they did the same thing for workstations.

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nsteel a day ago | parent [-]

HBM has a very wide, relatively slow interface. A HBM phy is physically large and takes up a lot of beachfront, a massive waste of area (money) if you're not going to use it. It also (currently) requires you to use a silicon interposer, another huge extra expense in your design.

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sroussey a day ago | parent | next [-]

> A HBM phy is physically large and takes up a lot of beachfront, a massive waste of area (money) if you're not going to use it.

The M3 Max dropped the area for the interposer to connect two chips, and there was no resulting Ultra chip.

But the M1 Max and M2 Max both did.

I have yet to see an x-ray of the M4 Max to see if they have built in support for combining two, have used area for HBM or anything exotic, but they have done it before.

Could you recognize HBM support in an x-ray?

As for the Ultra, they used to have 2.5 TB/s of interprocessor bandwidth years ago based on M1, so I hope they would step that up a notch.

I don’t put much stock in the idea of the 4 or 8 way hydra. I think HBM would be more useful, but I’m just a rando on the interwebs.

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sroussey a day ago | parent | prev [-]

> It also (currently) requires you to use a silicon interposer, another huge extra expense in your design.

Guess what the Ultra chips use? That’s right, a silicon interposer. :)

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nsteel 13 hours ago | parent [-]

OK, but that's an ultra expensive chip, pretty much by definition. The suggestion was to burden other products with that big expense, and that doesn't make sense to me.

	▲	sroussey 9 hours ago \| parent [-]
		I guess I was pointing out that they already do that with the UltraFusion interconnect that’s on the Max chip found in notebooks but never used there. But the more I think about it, the more I bet they are creating a native Ultra chip that is not a combo of two Max chips. I bet the Ultra will have the interconnect so you can put two together and get the often rumored Extreme chip. They will have enough volume for their own datacenters, that the Mac Studio and Mac Pro will simply be consumer beneficiaries. It makes more sense in this framing to put HBM on these chips. And no DDR5. In this case, the M4 Max has neither HBM nor the interconnect. I’d love to see someone de-lid and get an X-ray die shot.