Xbox One vs PS4: ESRAM slower than GDDR5, It's Bottleneck"

[Pemalite]

drkohler said:

Pemalite said:

Then you need to elaborate.
No point claiming someone is "wrong" and not even bothering to back up such claims, you just wasted my time with reading that for no gain or benefit to any parties involved.

drkohler said:

binary solo said:

If MS did actually think about delaying Xb one in order to put in GDDR5 ..

That never happened. Once they decided on the memory system (which likely was the second decision after the cpu decision), there was absolutely no way of changing the path. This is so fundamental in the whole process that if they changed that, they'd have to go back to blank sheets of paper.

No they wouldn't.
It would literally be as simple as swapping out the DDR3 with GDDR5 memory chips, Kaveri/Jaguar has dual-memory controllers which supports both memory technologies.
They might need to revise the PCB at most.

The latest Kaveri has two ddr controlers and two deactivated gddr controlers. That combination would get you nowhere console-wise (and this kaeveri is a low-end product). I'm not going to lecture about ram technologies, you can assemble the knowledge on the internet. However, these things are absolutes if ms switched from ddr to gddr memory at some point in time:

a) Complete redesign of the apu. Check the sizes of the four ddr3 and gddr5 controlers in the apu pictures posted on the web.

b) complete redesign of the motherboard (and to that effect the entre cooling system e.g. the whole system).

c) Find a customer for the terabytes of ddr memory you already ordered

d) Find a manufacturer for the terabytes of gddr memory you do not have.

To sum up again: Once a manufacturer has decided which cpu/memory path to take, there is no way back, come rain or storm.

I will ignore "a" it's mostly assumptions.

Redesign the motherboard? For what? Redesign the cooling system? For what? TDP isn't going to get much higher, Microsoft and Sony over-engineer their cooling systems anyway for worse-case-scenarios, hence why Microsoft was able to do the upclock.

C and D are valid points.
However, the DDR3 memory can find a home in Microsoft's other products, so it doesn't necessarily go to waste.

Besides, we were thinking in terms of theoreticals, a what-if scenario, it didn't happen and certainly can't happen now anyway, we have to put up with these underpowered consoles for several years now.

drkohler said:

ok, I will explain just one point most people got wrong (I have no hope this point will stick, though). I'm trying to be as "non-technical" as possible so that everybody can understand the conclusions.

One of the big question is: Who "does graphics" faster, the XBox One or the PS4 ? (without specifying what "doing graphics" exactly encompasses).

The correct answer is simple: It is the XBox One. Now this will confuse a lot of people. So in my endless patience, I'm going to tell you why and you will hopefully see why the esram is there. (As a sidenote, it is esram and not edram simply because the manufacturer doesn't have the 28nm technology, same reason the WiiU was designed in 40nm).

First we do the numbers game: We know the PS4 gpu has a specified bandwidth of 176GB/s into gddr5, and the XBox One gpu  has a bandwidth of 109GB/s into esram or a combination of esram/ddr3 (! a crucial point of the design that often gets overlooked, but that would be anther long lecture...). Now these numbers mean one thing, and one thing only: AMD's engineers tell us there is an absolute guarantee that in no way you can shuffle more GB/s than those numbers. What these numbers do NOT tell us how fast you actually shuffle memory around. So at first sight, we all agree: 176 > 109.

Now we take a second look and find that in reality: 176 < 109.

Now that may seem rather puzzling, but reality says it's true. Those numbers 176 and 109 come from the idea that you can shuffle data with every clock cycle. Unfortunately, noone is able to do this but in a mode that lasts just a few clock cycles. This mode is called burst mode and both apus can handle burst lengths of 8 (which means for eight clock cycles you get the stated maximum GB/s). After that, all hell has broken loose in the memory and you have to do a "calm down fellows detour". Now, without going into complicated explanations of how diffferent memory types are addressed, the "calm down detour" for the gddr5 chips (which in their hearts are just ddr memories) is much longer than the detour for esram. In a rather clumsy comparison, this looks like:

XBox: Grab with 109 GB/s Grab with 109GB/s ...

PS4:   Grab with 176GB/s Grab with 176GB/s ....

As you can see, the PS4's line is much longer in the end (in this cheesey comparison). The overal effect is that, on averafe, you grab less GB in the second case than in the first case.

Now it seems I have just written that XBox "does graphics" faster than PS4. Unfortunately there is another key element not yet mentioned.  "Does graphics" mainly means doing texture stuff and raster stuff. The PS4 has more of those than the XBox One. Twice as many rasterisers (very generous and maybe overkill) and 50% more texture units in the PS4 more than offset the slightly higher clockrate of the XBox One. What you want in the end is nicer/more pixels than the other guy and there is no way the XBox One can overcome the lack of TMUs/ROPs. So while it really can "do graphics" faster, it just doesn't have enough of those "does praphics" units to beat the PS4.

The thing about the eSRAM is that if the data isn't in the eSRAM then it has to be retreived from system memory, it's not going to be anywhere near 109GB/s under those circumstances.
Where it does shine is in multiple reads/writes to the eSRAM to all the other various pieces of logic at the same time.

The Playstation 4's memory latency in terms of clockrate should in theory be higher than the DDR3 and eSRAM which is what will give the Xbox One an edge in very few real-world cases.

But, you're just reafirming what I have said in previous posts, no amount of bandwidth will make up for hardware deficiencies, RAM/eSRAM and it's derivatives doesn't do any form of processing that is responsible for drawing the pretty pictures on-screen, it just feeds the brain that does handle that.