"Steamroller" and "Excavator"

BSN* claims Kaveri isn't getting a GDDR5 memory interface:

Kaveri doesn't get GDDR5 anymore

Earlier this year we reported about Kaveri also getting a GDDR5 memory interface, a rather interesting proposition but imaginable considering AMD integrated the same memory technology into the silicon for Sony's Playstation 4. A newer version of the NDA documents seen by us no longer include the references to a GDDR5 interface. The document detailing the GDDR5 interface was from last year, while the newer one we have seen is only a few months old. It seems AMDs engineers for some reason dropped GDDR5 in Kaveri. The possibility of models with 3 compute units (i.e. 6 cores) was removed as well. This is also reflected in the roadmap.
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http://www.brightsideofnews.com/new...aps2c-shows-28nm-kaveri-for-socket-fm22b.aspx

I'm not sure how that would have worked anyways without a pin count 'splosion. Available GDDR5 memory devices would have limited a 4 x 32bit GDDR5 interface to 1GB or 2GB (with 1 or 2 ranks supported per controller). With such small 128-bit GDDR5 memory sizes, a DDR3 interface would have needed to remain for main memory. The earlier leak may have been based on plans to counter Haswell's eDRAM cache, which largely benefits graphics.

Sheppard said:
I wonder what about gddr5 that makes necessary to solder the chips to the mainboard vs a slot like ddr3...
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The type of controller is meant to connect directly to a chip (usually 1 or 2 ranks per controller). There is no standard for GDDR5-based DIMMs anyways. GDDR5 memory is not electrically compatible with DDR3 memory chips, so you can't just stick them on a DIMM.
 
well yes, but whats to keep a company from creating a Gddr5 Slot, say on the other side of the cpu slot.
Regardless, amd would be smart to figure out a way to get that GPU on there the bandwidth it needs to shine. This is where AMD has a chance to knock one out of the park, and chooses not to.
 
There is no slot for GDDR5 it is on the mainboard or it is not. There is no other way to use GDDR5 beside being physically soldered on the device (be that mainboard or videocard).
 
I know there isn't a slot for gddr5 duh. The Playstation 4 uses 256-bit wide GDDR5 memory interface, with a memory bandwidth of 176 GB/s which is over 6 times the bandwidth of an IVY bridge with dual channel 1600. If AMD Strips the desktop variant of GDDR5, could you imagine how performance Crippling that would be? AMD needs to find a way of supporting the GPU with necessary bandwidth if they expect to make a splash on the desktop side.
 
Sheppard said:
well yes, but whats to keep a company from creating a Gddr5 Slot, say on the other side of the cpu slot.
Regardless, amd would be smart to figure out a way to get that GPU on there the bandwidth it needs to shine. This is where AMD has a chance to knock one out of the park, and chooses not to.
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What would stop that from occurring is trace legnth and the space near a cpu socket is usually already cramped with the DDR3 slots on one side of the socket and the power section of the motherboard on the other side. Now what I could see happening eventually is having some DDR5 chips directly on the motherboard as either a kind of cache or fast access memory to provide plenty of bandwidth for the integrated gpu, while retaining DDR3 slots for main system memory due to capacity constrains. This may be part of the reason why AMD is introducing HSA now to facilitate something like this.

I just recalled something sort of like this in old G5 Apple systems that has a so called "back side cache" that wasn't between main system memory and the cpu but still caching data for the processor.
 
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Kaveri isn't being stripped of an existing GDDR5 interface. The PS4's APU architecture is 2 quad core Jaguar CPUs grafted on to a GPU, and isn't comparable to desktop models.

Sheppard said:
well yes, but whats to keep a company from creating a Gddr5 Slot, say on the other side of the cpu slot.
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Nothing would. Performance would be degraded and without a standard, supply would be low and price would be insanely high.
 
Sheppard said:
I know there isn't a slot for gddr5 duh. The Playstation 4 uses 256-bit wide GDDR5 memory interface, with a memory bandwidth of 176 GB/s which is over 6 times the bandwidth of an IVY bridge with dual channel 1600. If AMD Strips the desktop variant of GDDR5, could you imagine how performance Crippling that would be? AMD needs to find a way of supporting the GPU with necessary bandwidth if they expect to make a splash on the desktop side.
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Imagine that the PS4 APU is embedded like a video card's GPU. Trace lengths will increase when you put memory on a DIMM, and high clocks seem to have issues with longer traces.

If the actual Kaveri die is small enough, could 256-512MB of GDDR5 be installed like Crystalwell on Haswell? I know 1+GB is out of the question for an eDRAM/PoP setup.
 
JMccovery said:
Imagine that the PS4 APU is embedded like a video card's GPU. Trace lengths will increase when you put memory on a DIMM, and high clocks seem to have issues with longer traces.

If the actual Kaveri die is small enough, could 256-512MB of GDDR5 be installed like Crystalwell on Haswell? I know 1+GB is out of the question for an eDRAM/PoP setup.
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It would be the rebirth of TurboCache! :D
 
Gman1979 said:
What would stop that from occurring is trace legnth and the space near a cpu socket is usually already cramped with the DDR3 slots on one side of the socket and the power section of the motherboard on the other side.
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Speed and probably would be out of spec for GDDR5 too. In order to get any sort of bus that fast enough to meet or beat top end iGPU Haswell they're going to have to at least solder RAM to the mobo and add a dedicated bus to the NB.

But that would mean a whole new chipset would be required and AMD's "FSB" as it is probably isn't fast enough to offer much advantage so that would have to be greatly improved as well. More realistically they'll put GDDR5 on package which is expensive but still easier than trying to add enough traces/pads to make GDDR5 soldered on to the mobo around the CPU socket work. It'll probably also be lots faster too. There is a reason why you see all these very high bandwidth buses/memory configs soldered either directly together on package or on a single mobo.

I suppose AMD could also release their new APU's in BGA format and just have the CPU soldered to the mobo with the GDDR5 RAM around the CPU package as well. That would work well too and maybe be cheap enough to make sense but the rumor mill hasn't even hinted at them doing something like that AFAIK.

Gman1979 said:
I just recalled something sort of like this in old G5 Apple systems that has a so called "back side cache" that wasn't between main system memory and the cpu but still caching data for the processor.
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There were old K6/Pentium/3-4-586 systems that had on mobo cache in a removable and upgradeable slot. Doesn't make sense to do that today since they're too slow and high latency for today's CPU/GPU.
 
JMccovery said:
If the actual Kaveri die is small enough, could 256-512MB of GDDR5 be installed like Crystalwell on Haswell? I know 1+GB is out of the question for an eDRAM/PoP setup.
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Sure. The die size isn't the problem. A CPU package can always be made bigger. The problem is heat and cost (yield effects this greatly + market forces, people probably won't pay $400+ for a APU that is maybe as good at gaming as a mediocre dGPU + CPU).
 
I am disappointed the road-map said two and four cores, i liked the idea of a six core Kaveri.

Not surprised that GDDR5 is off the table, never believed it. Always made more sense to me to opt for triple channel memory, and use the same socket for SteamrollerFX.
 
R3MF said:
I am disappointed the road-map said two and four cores, i liked the idea of a six core Kaveri.

Not surprised that GDDR5 is off the table, never believed it. Always made more sense to me to opt for triple channel memory, and use the same socket for SteamrollerFX.
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If Fm2+ is limited like FM2 100 Watt would be the reason for not having 6 cores.
The reason for GDDR5 is the bottleneck between GPU and memory.
 
R3MF said:
I am disappointed the road-map said two and four cores, i liked the idea of a six core Kaveri.
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I don't think you'll see a 6 core APU any time soon. They have to dedicate too much resources/TDP to the GPU for it to make sense. Maybe in a couple of process shrinks.

R3MF said:
Not surprised that GDDR5 is off the table, never believed it. Always made more sense to me to opt for triple channel memory, and use the same socket for SteamrollerFX.
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If GDDR5 is off the table then a triple or quad channel DDR3 is also probably off the table. You'd need one hell of a package to do quad or triple channel DDR3 memory and it probably look a whole lot like Intel's 2011 LGA when you're done. None of that is impossible to do but none of it is cheap or easy to do either and AMD's APUs have to be priced aggressively to sell. If they're stuck on dual channel DDR3 then next gen AMD APU's will lose performance wise vs. the top Intel Iris iGPU but will still be able to compete on price.
 
Pieter3dnow said:
If Fm2+ is limited like FM2 100 Watt would be the reason for not having 6 cores.
The reason for GDDR5 is the bottleneck between GPU and memory.
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i know why they might want more bandwidth, i just don't ever see GDDR5 as the answer when a triple channel DDR3 2133 would work very nicely at less cost.
 
In certain interviews AMD already said that it would never pursuit triple channel. And only quad for server purposes.
 
JMccovery said:
If the actual Kaveri die is small enough, could 256-512MB of GDDR5 be installed like Crystalwell on Haswell? I know 1+GB is out of the question for an eDRAM/PoP setup.
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ATI mobile GPUs had multiple memory devices added on package. That makes more sense than adding it externally due to the pin count.

It's certainly possible, if the GDDR5 could run at the temperatures near what the rest of the IHS gets up to. That's an issue 15-20W GPUs didn't have to face.

Stacked memory certainly is coming for situations like that.
 
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Damn, I was looking forward to a hexacore APU, but I guess it would be a bit unfeasible. I was wondering just how they'd get it done. A shame to see GDDR5 out too.

The thing that gets me is how the roadmap says Kaveri is still coming later this year, but in the recent Richland FM2 Newegg video, the AMD guy said "next year" when referring to Kaveri. He also said it'd still be on "Socket FM2".

Anyone know anything and care to clarify here, because as it stands we have a few contradicting statements lol.
 
Pieter3dnow said:
In certain interviews AMD already said that it would never pursuit triple channel. And only quad for server purposes.
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cheers, when did they say that?

still think a custom GDDR5 interface is les likely than AMD opting for the simpler option of triple channel DDR3.
 
still think a custom GDDR5 interface is les likely than AMD opting for the simpler option of triple channel DDR3.
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I would expect DDR4 being more likely than either option but it will not happen in 2013.
 
Hulk said:
Boys lets keep this thread under control. So should I upgrade to fx8350 and new motherboard now or wait a year till steamroller rolls around? Currently running a 965be with a non working motherboard. Another option I have is to just buy a cheap motherboard for the 965be and wait till steamroller is available.
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mate, get the best, most stable (8+ power phase) am3+ motherboard you can afford to buy, overclock the f*** out of that 965, and wait for steamroller! that is exactly what i am doing with my 955 :)

i dont really need the fx-8350, although it would be nice, but my 955 overclocked play bf3 multiplayer 64 players perfectly!! might just squeeze in a cheap 7950 to complement my overclocking :p
 
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