You raise a number of points still not justified effectively IMO. You say cost is a concern - what's the price difference between an APU using two different memories with two different buses versus using one pool of the more expensive stuff? Is that clearly quantitatively of the cards. You state high-end laptops are a no-go; ToT's link suggests very much otherwise, and shows a growth that AMD would have been aware of when (if) designing a high-end APU. And you state latency is a problem again. Is there any actual evidence that it is? Have you a link to an investigation of a PC OS running on GDDR versus DDR with significant penalties versus the benefits of the increased bandwidth?
No, I never said high performance laptops where no go. I said high performance APUs in laptops are no go, clear distinction. There are laptops out there with Quadro 5000 GPUs and 16GB of GDDR6 dedicated to graphics. There are alot of high performance laptops out there, but there are none high performing APUs and I gave the reasons why.
Creating high performance APU for laptop poses several design problems. As would be in this case, you would either have to go for very high amount of expensive, fast and power hungry RAM or you would split the memory.
Splitting the memory, like 100% of high performing laptops are doing these days, gives you ability to dedicate specific amount of fast RAM required for gaming tasks with second pool of RAM acting as system memory.
This is because apart from gaming, you will most likely spend more then 50% of your time working on actual productive things (or surfing or whatever) and design where 16GBs of GDDR6 in this case are used for 30 Chrome tabs, Netflix and Photoshop is just downright horrible. You are basically wasting fast, expensive RAM for tasks any memory will do ALONG with wasting considerably more power and pushing costs of laptop higher. Point is, DDR4 :
a) uses much less power then GDDR6 per GB
b) costs much less then GDDR6 per GP
c) sacrifices no performance in general system performance
And that is a reason why laptops have split RAM, especially in high performance gaming sector. If anything, single pool memory is used diametrically opposite, on lower end of laptop spectrum.
In case you go with single pool of GDDR6, you design yourself in a corner from beginning with higher costs and lower battery life without perceived performance benefit. In laptop environment, when Nvidia already has perf/watt advantage, that is already a lost battle before it has even started. This is why I just ask what would be the point of single pool of GDDR6 in laptop. It brings no benefits in this space and if it did, well surely there would at least be few percent of these on market. Instead, there is quite literally not a single one in existence.
Benefit of lower end APUs (which, all of them are and which is actually their main purpose) is the fact that you do not have to use fastest RAM out there, but DDR4 will do. It will give enough BW for most novice GPU tasks and plenty of battery life. Obviously, AMD is placing their APUs at lower end of spectrum because their advantage over Intel in this field is clear, but bringing APU into high performance space would lose them ALL the benefits, while further increasing their deficit in areas where they are already behind.
