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If they stick with UMA, gpu performance is going to be severely limited, unless they can make the unified memory GDDR6 or something.
by gameswithgo 6y ago
If they stick with UMA, gpu performance is going to be severely limited, unless they can make the unified memory GDDR6 or something.
- ksec 6y agoI would love to know as well. I think it could be HBM2, something similar to Fujitsu A64FX [1], the problem with both GDDR6 and HMB2 is that are limited in capacity to ~64GB, or at best 128GB. Which is far from the 1.5 TB of memory the current Mac Pro is capable of. [1] https://www.anandtech.com/show/15885/hpc-systems-special-offer-two-a64fx-nodes-in-a-2u-for-40k https://www.anandtech.com/show/15885/hpc-systems-special-off...
- dylan604 6y agoWhat if you gave the GPU its own dedicated memory again?
- ksec 6y agoThen it would make sense to have the two chip separate and not on the same Die. Which is essentially what the current PC system are doing. The whole hypotheses is built on Mark Gurman's suggestion of Mac Pro using something similar to SoC like the current M1.
- dylan604 6y agoWhy? Clearly, I'm not a chip designer, so maybe it's a dumb question. If you can place GPU cores, CPU cores, Neural Engine, and RAM on the same die, why can't you then use a second bank of RAM dedicated for the GPU cores? Why would this not be considered similar?
- wmf 6y agoThere's nothing stopping a chip from having HBM and, say, DDR5 DIMM slots but that has only been done once before by a doomed Xeon Phi. It's more likely that the future Mac Pro will use Lifuka which everyone in this thread is ignoring.
- marmaduke 6y agoXeon Phi is actually a pretty nice system to work with but as picky about performance as a GPU while more expensive and harder to find. Combining regular tool chains for code with high core count and SMT on top of AVX512 was nice. 68 cores, 4 way SMT, and 16 way SIMD, provides 4k “threads” in the GPU sense, except the memory hierarchy isn’t nearly as harsh because of the MCDRAM.
- ksec 6y agoBecause Lifuka; the GPU, hasn't had any other source other than the first Taiwanese publication. And those publication has been known to pop up all kinds of rumours only to pump up TSMC's stock price. And has relatively poor track record of any Apple information, or as a matter of fact, any information. It would be interesting if Apple did make a discrete GPU, that would means they are making a separate GPU die for their Mac Pro and iMac with volume estimated to be no more than 1M unit per year. It makes sense from a technical perspective, it surely doesn't from a cost perspective. Although Apple could happily charge $1000 just for the GPU to make up for ROI.
- wmf 6y agoYeah, it worries me a little that Apple thinks they can charge anything for the Mac Pro and probably iMac Pro. $10,000 starting price anyone?
- gameswithgo 6y agoWhether CPU and GPU share ram is orthogonal to whether the gpu and cpu are on the same die. You can do any combination of same die same ram, different die same ram, etc etc. The advantage of GPU having it's own memory is you can use super high throughput ram that the GPU needs, while using higher capacity/lower energy/cheaper ram for the cpu. The downside of using separate ram is that you have to shuttle data back and forth from one ram to the other quite a bit, as well you get less flexibility in how your total memory is used.
- an_opabinia 6y agoWhy couldn’t they? The 3090 ships with 24GB of GDDR RAM today.
- wmf 6y agoA future Mac Pro should support 1-2 TB of RAM which isn't really possible with GDDR.
- jmnicolas 6y agoGiven the premium Apple charges for RAM, I don't even want to "napkin calculate" how much a 2 TB ram Mac pro would cost!
- zimpenfish 6y agoIt was £200 to go from 8GB to 16GB which makes 2TB ... £51,200 or thereabouts.
- rthille 6y agoWell, on the current Mac Pro, going from 32GB to 1.5TB is $25K, but you also have to upgrade to the higher spec CPU @ $6K.