There were rumors for quite some time that Apple was developing its own discrete GPU alongside the all-in-one SoC packaging of the M-series chips.
Was the rumors really about a discrete GPU?
“… According to relevant sources, Apple's self-developed GPU is progressing smoothly. The research and development code is Lifuka. Like the upcoming A14X processor, it is produced using TSMC's 5nm process. Apple has designed a series of processors for Mac personal computers. The new GPU will provide better performance per watt and higher computing performance. It has tile-based deferred rendering technology that allows application developers to write more powerful professional application software and game software…..”
Apple will debut a powerful custom-designed graphics procesing unit in its first Arm-based iMac which is set to launch in the second half of next...
www.macrumors.com
This was a GPU for an iMac . Apple didn’t release a 27”, large screen iMac. They released the Studio with M1 Max and Ultra SoCs . Furthermore Lifuka is an island that is a part of ( subset of ) Tonga. The code name is indicative of something that is part of a whole. Not necessary something completely independent ( e.g. a complete discrete and detached GPU ) .
Apple did the Ultra . There is another GPU on another chip there ( relative to the primary die there in the package. ) . But it is not ‘discrete’ in the same sense that adjective is used in the general GPU discussions .
Decent chance folks were mapping there current understanding of the Intel iMac over the last 6-9 years .
Apple GPU going to use tile rendering …. that is like saying water is wet . They have done that all along since using the Imagination Tech baseline design . TSMC N5 … the whole M1 line up does. Performance per watt as major feature …. A Key feature of M1 Ultra reveal .
[ at one time pretty good chance there was a large screen iMac , but also extre likely that it shared SoC packages with the Studio . It highly like was not the GPU that suppressed that for now. Screen costs ( e.g. mini LEDs that didn’t scale ‘cheap’ ) , Studio Display priority , supple chain logistics , and/or market segmentation ]
Running a GPU that presents as a single GPU split over two dies would have been a research project .
It wouldn't be impossible that Apple might release Mac Pro chips as a new series outside of the M family (one that doesn't have to be updated as regularly) - CPU/Neural Engine-focused chips that that support modular GPUs and RAM.
Not impossible . Also not impossible that large meteor will fall out of sky and hit Apple campus center ring building like a bullseye .
Apple forks off a SoC package and Apple GPU driver stack that only works in the Mac Pro ? Probably not. The telling indicator is that Apple has put little visible effort into any discrete GPU driver stack develop ( both their own GPU or anyone else’s ) over last 18 months. skipping in 2020 is excusable as they were busy getting new OS branch off the ground. 2021 skipping again starts to more look like long term plan.
The rumors also point to a quad die M-seres solution to scale to a relatively massive GPU. That
entirely lines up Apple‘s driver work so far M1 ‘plain’ -> Ultra. Apple spends 10’s of millions developing the Ultra Fusion connectivity …. pretty good chance going to leverage that further in GPU space going forward.
Designing and manufacturing these sorts of custom parts for a small portion of the Mac market would no doubt be expensive, but given the current price points of the Mac Pro it wouldn't be a far leap. Doing so would free Apple to ramp up core counts on both the CPU and GPU without having to make the chip die impossibly large.
Modern 2.5 and 3D chip packaging means Apple does not need to go past 500-650mm^2 dies to scale. Apple may shrink the equivalent of the Ultra into a single die ( and just do a double Ultra )
Decoupling the CPU and GPU would mean Apple would need a new software stack that they don’t have now .
in most case , the bulk of the Mac Pro cost is not the CPU package .
8 core system $5,999 . W-3225 $1,199 -> 20%
16 core system $7,999 . W-3245 $1,999 -> 25%
Yes, the 24 and 28 core pacackes have both Intel’s “ > 1TB RAM “ tax and Apple’s “ pile on top” tax on them , but that isn’t the bulk of MacPro sales.
Furthermore Apple is already charging $2,000 to go from full M1 Mac to Full Ultra .
if talking a 3-6x more lower volume die , then the Apple markup is going to be about as many multiples of that $2k.
Apple should enable 3rd party ’compute’ GPGPUs but mainstream GPU that is detached from the Studio SoC apparoach is going to be quite small .