Durango dev docs said:
this has already been discussed in detail in some thread of other, so let's put an end to it. MS measured data across their bus. Over one second it as 100 GB of data. Over another it was 200 GBs. Over another it was 150. And they came up with an average attained BW of 150 GB/s. How can we be sure of this, you ask? How do we know that isn't 150 GB/s for one millisecond and the rest of the second it was only managing 100 GBs? Because 1) That figure makes sod-all sense when trying to communicate to your developers what resources they have at their disposal, and 2) the peak BE is 200 GB/s, so if Ms just wanted the biggest possible measurement, they could have contrived a scenario like that and reported, "we've measured 200 GB/s average use."Well yes, the other DF number strangely gives us more informationthe other one never mentions what its was from, how long a time step, what operations it was over, its just '150GB/s' is what we have achieved, when? how? for how long? what operations?.
The measurements are for developers. Real world measurement are far more useful for targeting an engine and assets than paper metrics.
Im pretty sure he means the XBONE GPU, not 1x the GPU
So how do you run a test without real code? Simulate it?
That's discussed in the other thread. One can add bandwidths together but it's a pretty meaningless value.
Yes. 150 GB/s for ESRAM and 60 odd for DDR3, means ~200 GB/s. How devs make use of that bandwidth is a complicated issue as it's not directly comparable to 200 GB/s of a unified RAM pool. For further discussion, how devs use the hardware as opposed to what the HW is, use the existing RAM discussion thread.
So how do you run a test without real code? Simulate it?
Anyway, MS just did throw out some arbitrary efficiency numbers in that interview without backing them up at all. Numbers from fillrate test from a respected hardware site (hardware.fr) got already posted in this forum (of course using using real code running on real graphics cards, basically the same as MS will very likely measure their bandwidth numbers) which prove, that alpha blending (also mentioned by MS as a scenario for getting more than 109GB/s out of their eSRAM) is good enough to realize 91+% of the theoretical bandwidth of GDDR5. Pure read (or writes) attain 93% in the tests using a Pitcairn GPU (that is reasonably close to the bandwidth and ROP configuration of the PS4).
So could you please stop to use the arbitrary multipliers. The most straightforward assumption is that this "efficiency" applies to both achitectures, XB1 and PS4, roughly the same way. For this kind of stuff the GPU is very likely able to use the available bandwidth with about the same efficiency, as long as proven otherwise. The picture is likely more complicated if you dive into the different characteristics of DRAM and SRAM (which we don't know in detail) and parallel use scenarios. But your grossly simplified approach is leading nowhere other than to fuel some crappy fanboy advantage arguments.
We had this topic already, conclusion was, they counted all SRAM, including the redundant stuff. That changes a few of the GPU numbers:
Thanks for the response. Since the MS guy was using "coherent read bandwidth" and framing it as the BET against other competing systems, it stands to reason that it was quite important. The big difference is the ESRAM and the audio blocks since most of the other stuff is shared by each system. As such the ESRAM would be the biggest contributor to the "coherent read bandwidth" difference. Seems to be a lot riding on that particular piece of real estate ;-)
Having it all laid out there when they state the coherent read bandwidth "bet" I think they are probably averaging up collective bandwidths and then parsing that out over the 47 MB ...say 47 MB / 140 GB/S ( just making that last number up ) for some ratio of memory to bandwidth or maybe just averaging the bandwidth. Just a supposition.
So forward going in terms of the BET the MS engineer suggests seems to be suggesting that their coherent bandwidth advantage ( depending on how that is defined ) will give the XB1 longer legs compared to some other not to be named system and it's GPGPU bet.
Ah another thread for that discussion.
Honestly I have no idea what you're talking about right now lol.
The Coherent Bus isn't connected to the ESRAM & it says that "Any DRAM data can be coherent with the CPU caches" it's 30GB/s but it's part of the 68GB/s DDR3.
Thanks again. So I was wrong in remembering the 47 mb as being coherent then
You can read and write from/into both ESRAM and DDR3, so no issue.
