"Allright guys how's it going"™ I'm pretty sure that we're all aware by now
that Polaris is going to be launching by the end of this month
so this will be my final analysis video on Polaris without having any of the
cards .
Now, one or two of you , have mentioned that I should probably point out that this is
speculation, all this stuff up till now is basically speculation but for me it's
not really speculation and this video will be explaining why . Is really all
about simple maths and knowing graphics card history ,is that combination, that
allows me to be so close with my predictions
I'm just gonna lay it all out in this video . Right, so the first place i'm going
to start with is specs
we've known for a while that Polaris 10 had one version with 36
CUs or compute units capable of more than 5 teraflops ,that alone gives
us a minimum clock speed of the card, we also know the memory size of 256 bits
there's some semi - new information on Polaris11 as well ,we can see that it's a much
smaller chip ,around about half the size, capable of greater than 2 teraflops
and with an 128 bit bus
so no great surprises here .This older slide, which i have used quite a lot
in the past, shows us that the memory size will be 4 or 8 gigabytes(GB) of
GDDR5 and also gives us a memory bandwidth of 256 GB per second
that memory bandwidth number
combined with the memory bit rate ,let's us know that it's using 8 GB/s
memory ,which is the fastest GDDR5 memory available and you also have a
number of a 150 watts of power
so here are all the RX 480's important specs
you've got the number of compute units which is 36, you can easily get
the number of stream processors from that, stream processors can be called SP
or Shaders or even cores
simply put : you multiply that 36 CU (compute unit) by 64 and you get 2304
Stream Processors .
Below that, we can see the boost clock of 1266 , where did I get that from ?
There have been leaks about this boost clock for the past two months and
all point to a 1266 MHz boost clock .
Here's one here from Computex I believe, 1266 MHz is pretty likely to be
the reference cards boost clock and by using 2304 stream processors multiply
that number
by 2, for 4608 and then multiply by the boost clock in GHz which is 1.266
gives you the 5.8 teraflops number . Stuff like texture units and ROPs, we
don't know about these, the texture units will definitely be right
ROPs I am not sure about, it could possibly be 32.
in all honesty these numbers don't mean an awful lot these days
texture units and ROPs are what used to bottleneck graphics cards a very long
time ago .
the RX 480 will basically have a choice of 32 or 64 ROPs .
I'm pretty sure will be 64 though, because they are selling it as a VR capable card.
ROPs are mostly useful for higher resolutions , so if AMD have only given it
32 ROPs and then attempt to sale it as a VR premium card, let's just say
AMD does a lot of silly things ,but this would be one of the more stupid yet
i'm pretty sure these numbers will be correct but they are not that important
so that is all the specs there that really matters most of these numbers only
really matter when comparing against other AMD graphics cards and we're
trying to figure out the likely performance range of the RX 480 the
best way to do it is against other AMD cards and then around this 5.8
teraflops level
so let's take a look at some other AMD cards around about this 5.8 teraflops
level ,and then i'm going to have a look at how architectural changes can make
the RX 480 either slower or faster than some of these cards .
So I'm going to start with the R9 380X
mostly because it's got pretty similar number of compute units and stream
processors, 32 on the 380x versus 36 on the 480 as you
already know by multiplying that number by 64 you get the number of
stream processors
if we just skip the boost clock right now we can see the teraflops of only 4
teraflops for the 380 x is quite a bit below the 5.8 of the RX 480
and that is simply because of the clock speeds, 1266 MHz divided by
970 MHz gives you a 31% higher clock speed
so if the R9 380 x had the same clock speed of 1266 MHz ,I would
have around about 5.2 teraflops, so obviously clock speed is pretty
important and the clock speed increase is a pretty natural
occurrence, whenever a new node arrives, the R9 380 x is of course based on 28
nanometer technology, where RX 480 is based on 14 nanometer FinFET
technology .
This is what has allowed AMD to increase the clock speeds by over 30%
here and basically speaking it's almost like free performance ,again the texture
units and ROPs, you can see that with 144 versus
128 texture units . That is not a huge gap because those are
tied to the number of compute units
and looking at the ROPs, the R9 380 x only has 32 ,now remember this is
speculation on the RX 480's ROPs ,it may only have 32 but i believe
it will be 64 .
If we now compare the memory, we can see that the memory bandwidth of the RX 480
is quite a bit higher and this is simply because it has got faster memory
on the same 256 bit memory bus ,and on the bottom we can see the R9 380 x
draws more power . So that's R9 380 x if you just look at those specs ,the RX480
should be clearly faster on this specs alone you would expect over 40%
faster performance from the RX 480 compared to the R9 380 x . Right ,
so now i have added the R9 390 x with 44 compute units
it is quite a bit ahead of the other two and of course with the increase in
compute units comes a corresponding increase in stream processors ,up to
2816 , because it is a 28 nm GPU however the clock speeds are a good
deal lower then RX 480
the combination of which means that the R9 390X is just ahead
in teraflops compared to the RX 480 . Once again because your texture units
are tied to your computer units, we have a higher number and R9 390X
does have 64 ROPs, again please remember that I am guessing that the RX 480
has 64 here .
so the R9 390 x is a little bit ahead there, which we can see simply by
comparing the teraflops . When we look at the memory ,however, the gap seems to
increase by quite a lot . Even though it's got slower memory, that is 6 GB
per second ,against the 8 GB on the RX 480,it has double the memory bus
width, 512 bits compared to 256 bits .
This means that, overall ,the memory bandwidth which with memory is the
important
number really, 384 GB/s compared to only 256 of the RX 480
that is a big gap and right down the bottom
we can see that it is a much more power hungry card ,275 watts compared to 150 .
If you just look at the specs overall , it doesn't seem to be any real chance of
the RX 480 beating the R9 390X, especially with the gap in
memory bandwidth, but in order to see if that is really the case
let's take a closer look at the GPU itself and some of the changes in
Polaris, to see if Polaris can overcome these deficits or not
so here's a block diagram of the R9 380 x
all those CUs we've talked about ,we have 8 CUs per shader engine ,
so if u just count those up, 8 x 4 =32 .
this RB here is your Render Backends each of which has 4 ROPs
and 8 x 4 = 32 . So 32 CU's and 32 ROPS which is
exactly what the chart shows : 32 compute units ,32 ROPs .Now this is
a block diagram of the 390x . Straight away we can see that the ROPs have
doubled
which means 64 and instead of 8 compute units per shader engine we
can see that is 11 . 11 compute units, 4 shader engines and there's your
44 compute units and again your 64 ROPs ,so if RX 480 has only
32 ROPs it will look very much like this
the only real difference being ,an extra compute unit per shader engine ,with ,
in my opinion
double the ROPs ,but if you go back to the RX 480
versus the R9 390X, how can it beat the R9 390 X when it
loses in specs ,especially on that memory front . Well, let's deal with the memory side
of things first of all . In this benchmark here over at TheTechReport, using
beyond 3D's bandwidth benchmarking test you can see here the difference between
black textures and random textures regarding bandwidth,what this actually shows is
is how well memory compression works on each of these cards ,so the solid bars
here
show the amount of bandwidth in GB/s that each card is using, while
drawing a completely black texture on the screen . When you run a random texture
through the same benchmark in some cases we can clearly see the difference
is interesting to see just how much better Maxwell is compared to the
rest
that is your GTX 980, 980Ti and Titan X . The memory compression on these cards is
much better than what is ,on for example : the GTX 780 ti and even the Fury X
but what's interesting here is that the Radeon R9 290x which as you probably
know is the same silicon ,basically the same card as the 390 X, it is
showing no difference whatsoever between the black texture and the random texture
and the reason for that is simply : the R9 290x and the R9 390x do not
have any kind of memory compression technologies whatsoever
you may also notice that the R9 290x is not capable of reaching its maximum
memory bandwidth, in this case that would be 320 gigabytes per second, so is
falling short of the capability of saturating all of its memory bandwidth and
they don't even have any memory compression at all
the reason for which is : the 290x, the 390x, are based on slightly older
Graphics Core Next (GCN) revisions
AMD did add some pretty good compression later on, it was initially added to their
Tonga class of GPUs , that is their R9 285 which became the R9 380 and
the R9 380 x . And here we can see the difference between R9 285 and R9 280
even though the R9 280 had a bigger memory bus
it did not stop the R9 285 beating it quite easily, but there's more to it
than just that , if we look at this old slide of the Polaris architecture ,we can
see all the stuff that is new
what is interesting here in terms of bandwidth, could be the new L2 cache, the
L2 cache is basically just memory on the graphics chip itself
storing data in L2 cache is much more efficient than storing data in memory
off the chip . So the stuff that is used most often gets stored the L2
and rather than having to make a trip out to the memory on the graphics card
which requires more bandwidth ,a much more efficient way of getting
performance out of a new graphic chip is by improving the L2 cache
there are a couple ways to do this, it will improve naturally, with higher clock
speeds which are of course a result of the new process . There are other ways to
do it as well though. For example, in the case of the 380x here and even in the case of
the 390X
these cards had 1MB of L2 cache, so, is it possible that with the new node
the RX 480 may have a larger, faster L2 cache
these are just things that we expect to come from a new process but the
important thing here is : all these numbers,
the 384 GB/s of memory bandwidth it's not the be and end-all
even with only half of the memory bus width I would expect the RX 480 due to
having advanced memory compression and due to having faster and possibly even
larger L2 cache
I would expect the RX 480, to have a faster, more efficient memory subsystem then
R9 390 X .
So now we've got 2 graphics cards that should be very very close together
the only real difference being this point 0.1 teraflop, but that still means
that RX 480 will be a little bit behind
unless it can make up the difference elsewhere, so what improvements can
actually be made to make the RX 480 faster than R9 390 X .
Well, if we take a look at the Polaris architecture improvements ,again ,we can
see a new Command Processor, a new Geometry Processor and new 4th
Generation Graphics Core Next CUs .
Now, generally speaking, from architecture to architecture, these
things improve
you certainly don't try to make them worse, but it's not always that simple
now, the new geometry processor, we really don't know a lot about that
but in the past ,we saw a slide mentioning the Primitive Discard Accelerator
we've got no idea what this does yet, but given the name we can sort of figure out
that the whole point of this is to get rid of unused primitives, basically so
that the engines aren't wasting time drawing stuff that isn't on the screen
so that should just cause an overall improvement and if we then look at the
4th Generation Graphics Core Next CUs
the whole point of improving these is to get more performance on a per CU basis
for one of a better term, if we just think about it as CPU IPC
(instructions per clock)
all of these improvements together, even with only 36 Compute Units, compared
to the 44 of the 390x, all of those improvements should effectively
left the RX 480 up to a level which is approaching the R9 390X
in simple terms, those 2304 stream processors could theoretically be
working just as well as 2816 of the R9 390X .More likely though, we may be
looking at say
5 -10% increase , so let's just take 10% ,which is a nice
easy number, that would mean that RX 480 has the equivalent of 2534 stream
processors and if you multiply that number by 2 and then multiply that
number by 1.266 again
you now have 6.4 teraflops of performance , that assumes the AMD has
made a progression and not a regression . It is possible, it has been clear from the start
that Polaris was designed to be a very low power architecture
so it is certainly possible that rather than increasing performance per
Compute Unit ,performance may have regressed instead . Simpler shaders to
save power .
So this is something that may happen and if the card cannot match the
R9 390X that is the likely reason why . There's a second reason and
that is of course drivers, new architectures take longer for drivers to
mature . Similar story could happen here,
even though it's still GCN ,there maybe driver issues there ,which prevent
RX 480 from showing it's true performance from the start
I'm not sure I believe that one tho, because AMD has had silicon in their
hands since last November, so I don't believe that drivers are an excuse here
for me though, is rather simple , the RX 480 should beat the R9 390X
there's been a lot of rumors suggesting otherwise but, based on the raw stats
and based on the fact that AMD should be increasing
IPC, i believe that is the far more likely probability here
there is of course one final way to improve performance : the clock speed of
1266 MHz , I am quite sure will not to be near the limit of this card.
AMD had a big problem on 28 nanometers
they simply could not overclock their cards very far and power numbers shot
through the roof whenever you tried
so they were very much limited by power and the 28 nanometer process , the
14 nanometer FinFET process should really help a lot with clock speeds and
the most recent rumors like over at WCCFTech
are suggesting around about 1500 - 1600 MHz which if true
the RX 480 at around 1500 MHz ,cannot be far away from Titan X performance at
least in DirectX 12 games .
We shall know all about that very very soon. Right , so that's it for this one
I just wanted to do a bit more educational video, I wanted to point out
have I come to these conclusions
it's just logic ,it's just numbers, it's just the history of graphics cards, all
that can happen now is that we are pleasantly surprised or unpleasantly
shocked
let's hope for the former and let's hope for a 200$ graphics
card .
The likes of which we haven't seen in a very very long time .
That's what I am hoping for from AMD here . But ,like I said that is me done
with the speculation and the conjecture for Polaris . The next stuff you hear about from me
Is going to be factual . In the meantime though
I've got a benchmarking PC to build so look out for that one soon(TM)
I'm going to be really really busy from now until the end of this month but ...
" I will catch you later guys "
yeah
d(O_O)b