Xbox One (Durango) Technical hardware investigation

[Kaotik]

Not commenting on anything else, but DDR4 isn't "paper RAM", it's been ready for quite some time and can be produced in mass quantities if someone wants it.

 

[MrFox]

From what I read, DDR4 is supposed to launch at 2133 anyway for mass production, but I'm curious if it could be less expensive in the long term, because it's the lowest bin of DDR4, while DDR3-2133 is the top, most expensive bin.

 

[MfA]

Not commenting on anything else, but DDR4 isn't "paper RAM", it's been ready for quite some time and can be produced in mass quantities if someone wants it.

If someone wants to pay through the nose for it ... until it's actually used in PCs it's boutique, even moreso than GDDR5.

 

[Grall]

Not commenting on anything else, but DDR4 isn't "paper RAM", it's been ready for quite some time and can be produced in mass quantities if someone wants it.

It was called "paper RAM" I suspect because nobody's making it in quantity, it is not scheduled to be produced in quantity for quite some time and if anyone wants it right now they'd have to pay boutique prices for it instead of commodity, since there's no competition driving prices down.

 

[Scott_Arm]

DDR4 would mean a different memory controller in the APU as well as a new PCB layout for address bus, data bus and command signaling, plus whatever differences there are in clock, power and whatnot.

Edit: meaning incredibly incredibly unlikely if the kits had been going out with DDR3 recently.

 

[Lalaland]

http://www.vgleaks.com/world-exclusive-durangos-move-engines/

Lots of detail already leaked, probably from official MS doc.

Cheers DrJay not sure how I missed that after 80 pages of lurking! So they are just DMA engines with two having additional JPEG/LZlib functionality. Are these a good thing in and of themselves or a good thing because of the ESRAM/RAM split? Can they read/write from CPU cache (not in the article but it would seem like a useful feature to me as an ignorant forum lurker)?

 

[Lalaland]

It was called "paper RAM" I suspect because nobody's making it in quantity, it is not scheduled to be produced in quantity for quite some time and if anyone wants it right now they'd have to pay boutique prices for it instead of commodity, since there's no competition driving prices down.

Spot on, I was indulging in hyperbole after a long day at work! My meaning was that while it may be a spec until someone has invested significant amount of cash to start fabbing it, that's all it is. I'd love to hear if it has been produced in quantity as I want me some for my PC!

 

[dobwal]

I was looking through some AMD patents specifically the ones dealing APUs (APD is the term AMD likes to use in their patents). I was looking mainly at their patents dealing with QOS, pre-emption and context switching, which is basically part of their 2014 roadmap.

There are several patents involving pre-emption and context switching. As I was going through the patent drawings which are commonly shared across these patents I noticed what AMD labeled as memory 130. I though nothing of it at first because it vaguely described in most of the patents.

Within the system 100, APD 104 includes its own memory, such as graphics memory 130 (although memory 130 is not limited to graphics only use). Graphics memory 130 provides a local memory for use during computations in APD 104. Individual compute units (not shown) within shader core 122 can have their own local data store (not shown). In one embodiment, APD 104 includes access to local graphics memory 130, as well as access to the memory 106. In another embodiment, APD 104 can include access to dynamic random access memory (DRAM) or other such memories (not shown) attached directly to the APD 104 and separately from memory 106.

However this patent explains the memory 130 a little more.

Accessibility of graphics processing compute resources
http://www.google.com/patents/US20120229481

After the processing of work within graphics pipeline 162 has been completed, the completed work is processed through a render back unit 176, which does depth and color calculations, and then writes its final results to memory 130.

In this document, the terms “computer program medium” and “computer-usable medium” are used to generally refer to media such as a removable storage unit or a hard disk drive. Computer program medium and computer-usable medium can also refer to memories, such as system memory 106 and graphics memory 130, which can be semiconductor memories (e.g., DRAMs, etc.). These computer program products are means for providing software to unified computing system 100.

Maybe, the eSRAM in Durango isn't simply a MS's invention based on cost savings but a reflection of AMD's intention of using eDRAM or eSRAM in its future post 2013 APUs.

 

[BRiT]

It was called "paper RAM" I suspect because nobody's making it in quantity, it is not scheduled to be produced in quantity for quite some time and if anyone wants it right now they'd have to pay boutique prices for it instead of commodity, since there's no competition driving prices down.

The exact same thing can be said for "8GB GDDR5."

It seems like "paper RAM" will be used all around.

 

[Rangers]

Maybe, the eSRAM in Durango isn't simply a MS's invention based on cost savings but a reflection of AMD's intention of using eDRAM or eSRAM in its future post 2013 APUs.

plausible to likely, given high end haswell has edram.

 

[MrFox]

The exact same thing can be said for "8GB GDDR5."

It seems like "paper RAM" will be used all around.

Still, there's a huge difference between a new type of RAM that is untested and needs a new controller design, and a mere capacity bump from an existing production, with a proven controller.

Using GDDR5 4Gbits is very low risk, and has no impact on any design choices nor on the SoC design. They can plan everything with 4GB and switch to 8GB at the last minute if a supplier can do it within the time and budget limit (this is probably what happened). Capacity increases always come with new nodes and there's no doubt about volume, all GPU cards will start using 4Gbits at a predictable pace.

OTOH, DDR4 is high risk. It needs an SoC designed from the start with early non-final specs, there are chances of delays, chances of specs changes, and there are no backup plans, the whole console will be delayed if DDR4 is delayed, they can't go back to DDR3 at the last minute if there's a problem.

The question is why would they take that risk instead of going with DDR3, if it provides the same performance anyway? Sure DDR4 will eventually cost less, but when? A launch delay for a console is a pretty big deal

 

[AlphaWolf]

Specs for ddr4 aren't exactly recent, Samsung first sampled it over a year ago. If someone wanted to design a system around it I doubt you're looking at serious issues.

 

[Rangers]

I do recall the original Durango rumors centered on DDR4. Remember that? The reasoning was it would be cheaper down the line.

Later it was said to be DDR3, although I dont recall if that was clarified as final, or just what was in the dev kits.

In performance (bandwidth) terms it shouldn't matter much.

I'm not sure if the DDR4 densities would allow for a increase to 12/16GB on 256 bus where DDR3 would not? That type of thing is above my pay grade.

 

[MrFox]

8GB or even 16GB capacity aren't an issue with DDR3. You can do 32GB easily on 256bit with inexpensive parts.

 

[Scott_Arm]

What exactly would they gain if they switched to DDR4, assuming they keep the memory clocks the same? Don't know what the bandwidth advantage is. Isn't it a little unlikely to send out specs showing memory bandwidth between all of the parts of the system, including Move Engines, and then change it all last minute-ish?

 

[Rangers]

supposedly the thought was ddr4 will be cheaper than ddr3 in the future.

in a few years presumably ddr4 would be in it's prime while ddr3 being phased out thus more expensive.

 

[Gradthrawn]

Did some quick Googling about DDR4 and found this interesting little article about its current roll-out and adoption.On a side note, it appears to offer some nice power savings over DDR3 (not to mention bandwidth):

The latest PCs and servers come with DDR3 SDRAM, and mobile devices have just started getting a type of low-power memory called LPDDR3 (low-power DDR3). DDR4 is the successor to DDR3, and consumes 20 percent to 40 percent less power while offering double the throughput of its predecessor.

I'm not implying anything about its possible use in the Durango, I just thought the article was interesting.

 

[McHuj]

I think Durango can potentially move to DDR4 down the road. DDR4 will certainly meet the bandwidth requirements and if the latency is as good (or better than DDR3), there maybe a cost revision down the line (maybe in 2014 or so) with DDR4. To that software that could be transparent, but the power savings should help.

 

[dagamer]

I think Durango can potentially move to DDR4 down the road. DDR4 will certainly meet the bandwidth requirements and if the latency is as good (or better than DDR3), there maybe a cost revision down the line (maybe in 2014 or so) with DDR4. To that software that could be transparent, but the power savings should help.

Why would the power savings help in a device plugged into a wall? It's not a mobile device, the benefit certainly doesn't outweigh the risk at this point.

 

[AlphaWolf]

Less power equals less cost to dissipate the heat as well as savings on the psu. Cooler components will typically last longer as well.

What risk?