The more I think about it, the more true that seems to be - they're point-versions apart in terms of technology, e.g. 1.0 and 1.1, but calling them 1 and 2 has a warm and fuzzy marketability to it.
It may be more than 0.1, if it turns out that HBM1 is SDR and HBM2 is DDR. That seems like enough of a change for a .5 or more. The legacy mode, if that turns out to be an actual legacy mode, might speak to a planned evolution for the standard. Maybe the original intent was for HBM1 to serve as the initial somewhat-rough effort that would have gone into graphics earlier, and the legacy mode is something to compensate for the time lost.
Old threads are so much fun, I get lost in them for hours at a time:
Nvidia GT300 core: Speculation
NVidia never did the memory hub. And, Aaron was convinced that GDDR5 would never get to the speeds it's now reached. Differential signalling was the dead-certainty. Did XDR2 ever appear in a product? Dare I utter the word "Rambus"
I am not aware of a XDR2 being used. The motivation for the hub concept seems lost, since memory didn't change much in the years since. HMC is something like it, but it uses stacking to eliminate one half of the high-speed IOs that the hub concept presented.
IBM's Centaur memory buffer may mean that HPC installations with Nvidia will have a buffer on the CPU side, although the reasons would be different.
In the face of the physical constraints of transmitting over a PCB, GDDR5 has managed to use 6 years to hit the 7 Gbps threshold, with potentially some future product nudging to 8 Gbps.
Perhaps the skepticism was stemmed from the expectation of a GDDR6 in the intervening half decade, which could ill afford to start at the top end of GDDR5 with nowhere to go without differential signalling.
Hybrid memory cube is the next high-speed over PCB standard, which is differential.
HBM gives up on the PCB and the high speed.
I was uncertain at the time if another vendor would want to get in on an AMD memory standard, given how unhelpful it turned out to be for the last one. HBM seems to indicate there was still a case for such a collaboration on niche memory, while HBM1 vs HBM2 feels like the same conditional benefits are in play.
Could we see HBM1 stacks as salvage variants of HBM2? e.g. the stack consists of HBM2 dies, but with large chunks turned off or de-rated, therefore good for only HBM1?
If the signalling is different, I am not sure how that works unless legacy mode effectively behaves like SDR HBM2.