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New processor system will be built on TSMC's new smaller transistor node

Advanced Micro Devices Inc. (AMD) and its fab partner Taiwan Semiconductor Manufacturing Comp., Ltd.'s (TPE:2330) (TSMC) are reportedly preparing an upgraded version of the system-on-a-chip (SoC, or APU (accelerated processing unit) in AMD lingo) that powers the Xbox One.

I. A LinkedIn Leak

The coming upgrade was revealed in a careless addition to the resume of an AMD manager on LinkedIn Corp.'s (LNKD), an addition which was quickly noted by "Mosen" on Beyond3D's Forums.

What does this mean for Microsoft Corp.'s (MSFT) console?  Well currently the console's processing is driven by an AMD SoC with 2x 1.75 GHz quad-"Jaguar"core modules (8 total CPU cores) + 853 MHz Radeon Graphics GCN 1.1 (Graphics Core Next) module with 12x units w/ 64x cores per unit.  (The on-die GPU is derived from the Hawaii die found in the Radeon R9 290X, a Volcanic Islands series GPU.)

Xbox Motherboard
The Xbox One's SoC (center) is due for an upgrade. [Image Source: PC Perspective]

The source of this new info is Toronto, Ontario, Canada area engineer Daniel W. McConnell.  According to his LinkedIn resume, Mr. McDonnell spent seven years at ATI (1999-2006) before the acquisition of the GPU maker by AMD.  Since the acquisition, he's spent the last eight years working as an AMD senior manager, most recently managing the console SoC unit.  Assuming the leak wasn't purposeful on AMD's part, we can only assume that he made an innocent mistake, not realizing his LinkedIn resume was visible to the public.

He's since made his resume private, but here's a somewhat redacted version that we managed to get (click for full resume):
David McConnell
As originally noted by "Mosen" in the forums of the blog Beyond3D, the "Senior SOC Physical Design Manager" entry under the "Experience" section previously had a lot more bullet points with some interesting information.  It read:

Currently managing a global team of 80+ PMTS, SMTS, MTS, Senior and Junior Engineers for the XBOX One APU with a planning horizon of 12-24 months.
  • Successfully planned and executed the first APU for Microsoft’s XBOX One Game Console in 28nm technology and a cost-reduced derivative in 20nm technology.

  • Drove technical management to support project teams across multiple geographic locations simultaneously including internal IP, CAD and RTL teams to meet the project schedule.

  • Operated as the Physical Design interface to the Microsoft XBOX team resulting in an excellent relationship that has aided in contract negotiations and conflict resolution between the two companies.

  • Developed secure flows for customer specific secure IP. This flow was executed on the original product and was then carried forward to 2 successive SOCs.

  • Aggressively drove down product costs through area saving initiatives like increased tile utilization and working with IP’s to reduce area, resulting in several million dollars of savings over the ASIC lifetime.

  • Assembled and grew two cross-site execution teams for 2 successive XBOX APU revisions. This included developing key technical leads into senior positions allowing for successful execution and future team expansion to handle more SOCs.

  • Regularly presented program status to AMD and Microsoft senior executives, communicating risk mitigation plans to keep the project on schedule.
The items in bold were deleted soon after EuroGamer caught wind of the forums post and wrote an article.  The resume has since been made private as in only accessible if you have a LinkedIn account.

II. The Timing Adds Up

Does the timing of this supposed die shrink add up?  In a word -- yes.  

2014 has been an off year for AMD in terms of die shrinks, but 2015 should look a lot more like 2013, when AMD introduced the Volcanic Islands and Sea Islands GPUs.  According to leaks site WCCF Tech, the first 20 nm design will be released in H1 2015 and will be dubbed Pirate Islands.

Here's the roadmap on the GPU front:

  Pirate Islands Volcanic Islands Sea Islands Southern Islands Northern Islands
Manufacturing process 20nm 28nm 28nm 28nm 40nm
Time of Release 2015 2013 2013 2011 2010
First Product To Release TBD Hawaii/290 Bonaire/7790 Tahiti/7970 Cayman/6970

In a piece from Sept. 2014, WCCF Tech writes:

The [20 nm] GPU architecture will be integrated into all of AMD’s future GPU and APU products, including ones based on project Skybridge, so we’ll see this architecture in low power ARM based SOCs as well as good ol’ APUs which bodes very well for its potential power efficiency and scaling.

If the leak is correct (which it likely is), it would stand to reason that the console APUs would be due for a shrink as well.

On the GPU side, as seen above, AMD has been seeing dies shrinks roughly ever 3 years.  It had shrunk from 55 nm to 40 nm midway through the R700 family rollout.  Specifically the M97 die (Mar. 2009: Mobility Radeon HD 4830/60) and RV740 die (Apr. 2009: Radeon HD 4750/70) were based on a 40 nm process.

And in Jan. 2012 it launched the Radeon 7000 Series (Southern Islands) which shrunk to a 28 nm process (first cards were the Radeon HD 7950/70 based on the 28 nm Tahiti die).  So Mar. 2009 and Jan. 2012 were the last two die shrinks; so one would expect a GPU die shrink will be released in the wild sometime in Jan.-Mar. 2015.

On the CPU side (non-console), AMD has been executing a faster series of die shrinks, albeit at smaller intervals (1-2 years).  The last APU die shrink came with the Kabini/Temash APU families in 2013, which jumped from a mix of 40 nm TSMC chips and 32 nm GLOBALFOUNDRIES chips to TSMC's 28 nm process.

Kaveri A Series


Kaveri
The Kaveri APUs from AMD are similar to the APUs found in the Xbox One and PS4, but use Steamroller cores, rather than groups of the lighter weight Jaguar cores. [Image Source: AMD]

It's reportedly prepping 28 nm APUs based on GLOBALFOUNDRIES' new 28 nm process, as well.  These chips are dubbed Carizo, and are set replace this year's Kaveri early next year.  They swap out the Steamroller cores found in Kaveri for Excavator cores.

So both on the GPU and CPU side, this die shrink is in line with everything we know.

III. How Will Going to 20 nm Affect the PS4 and Xbox One?

What does that mean for the Xbox One?  In a word -- "slim".

A similar die shrink for Sony Corp.'s (TYO:6758PlayStation 4 (PS4) shouldn't be too far behind, but the PS4's higher power consumption calls into question whether 20 nm will be enough to allow a "slim" edition SKU.  For the Xbox One, though, which already has a roughly 25 watt lower in-game power draw, the case is more clear cut, though: this will almost surely allow a "slim" Xbox One.

The difference between the impact of 20 nm on the PS4 vs. Xbox One may seem a bit confusing, but bear in mind this general premise: the two are powered by very similar chips, but there are slight differences between the cores on the memory and graphics fronts.  These differences are reflected in power consumption.  According to a study [PDF] by the National Resources Defense Council (NRDC), an Xbox One draws 112 watts during gameplay versus 137 watts for a PS4.  

NRDC power consumption
[Image Source: NRDC]

The first major difference between the cores is the memory.  The PS4 packs 8 GB of GDDR5 with a theoretical bandwith of 176 GB/s (Gigabyes per sec.).  The Xbox One packs 8 GB of DDR3 with a theoretical bandwidth of 68.3 GB/s.  So the PS4's memory is roughly twice as fast.  But the Xbox One carries a special on-die 32 MB cache of ESRAM (embedded static RAM), which has a theoretical bandwidth of 192 GB/s -- a chunk of memory that is marginally (1/11th) faster than the GDDR5 used in the PS4.

Xbox One SoC
The Xbox One features a fast cache of ESRAM. [Image Source: Microsoft]

Of course real world performance of both memory schemes likely falls short of the theoretical bandwidth (e.g. Eurogamer reports the ESRAM was achieving 133 GB/s -- roughly two-thirds of its theoretical bandwidth.)  But suffice it to say that that what at first glance appears to be a clear cut win for the PS4 becomes a more complicated comparison upon closer inspection.

Xbox One SoC

Xbox One
The Xbox One features a nearly identical pair of CPU core packages to the PS4, but differs on the memory and GPU fronts. [Image Source: Microsoft]

The Xbox One's use of ESRAM is interesting as this means that it could get a memory boost from going to 28 nm to 20 nm, as the memory is on the SoC.  This is not the case for the PS4, whose memory is wholly off the die in GDDR5 chips.

The difference is much more stark with the GPUs.  Performance wise the picture is not so rosy for Microsoft, but in terms of power consumption, its leaner on-die graphics give it the edge in terms of rolling out a slim console.  The Xbox One's Durango GPU has less available cores than the PS4's Liverpool GPU.  The dies for the Xbox One and PS4, respectively have 768 shading units (SU) (12x compute units, or CUs) / 48 texture mapping units (TMUs) / 16 ROPs and 1152 SUs (18x CUs) / 72 TMUs / 32 ROPs [further reading].

Microsoft has compensated slightly by bumping the clock speed of its SUs from the 800 MHz the PS4's SUs operate at to 853 MHz (a 1/15th speedup).  But the PS4 remains the more powerful GPU when the SUs are fully loaded, given its significant edge in SUs.

So the Xbox Durango GPU consumes less power because it has less process power.  Further, the PS4 is a more compex design with 8 asynchronous compute engines (ACEs), which allow it to process 64 simultaneous compute instructions on SUs that the graphics pipeline isn't currently using.  The Xbox One, by contrast has 2 ACEs, enough to simultaneously process 16 compute instructions.

AMD ACEs

AMD ACEs
The Xbox One has a quarter of the GPU Compute queues as the PS4. [Image Source: AMD]

This means while the graphics may be similar on the Xbox One and PS4, the PS4 likely has extra SUs for general purpose GPU (GPGPU) computing, allowing it to accelerate physics or AI algorithms.  The upside is that while it lacks the PS4's prowess in GPGPU compute, the Xbox One consumes less power as a result.

IV. Slim Xbox One Could Trim $50 Off the Price, be a Third Skinnier

All of this adds up to the fact that a die shrink to 20 nm could save it enougn power to enable a "slim" variant of the Xbox One.

TSMC's information on the die shrink from 28 nm to 20 nm state an average power savings of 25 percent power (at constant clock speed). So assuming that 80-90 percent of the Xbox One's power consumption is in the SoC, this indicates that the Xbox One with the new chip should be drawing around 90-100 watts.  

Xbox One
[Image Source: GenGame.net]

By shaving nearly 25 watts (at maximum) off the TDP, the Xbox One is very close to being able to drop the large 112 mm fan in lieu of a large copper heat sink.  On desktops, parts suppliers like Quiet PC have fanless copper coolers for chips < 95 watts TDP.

As we see from iFixIt's teardown of the console, the fan is one of the tallest components of the console.  With a metal passive cooling system for the new SoC, a slimmer hard drive mount, and a slimmer Blu-Ray disc drive, Microsoft should be able to trim up to a third off its console height-wise.
Xbox One Fan
The Xbox One's fan adds substantially to its height. [Image Source: iFixit]

The slim console may also be priced slightly lower as Microsoft (according to Eurogamer) is currently paying roughly $50 USD per SoC from AMD.  Going from 28 nm to 20 nm increases yields 1.9x, according to TSMC.  So theoretically Microsoft should be trimming $20-25 USD off its bill of materials.

Microsoft recently announced a holiday promotion where it will offer the Xbox One without Kinect 2 (originally $399 USD) for $349 USD.  The lower cost of the processor brains of the console could help Microsoft make that cut permanent and trim the price of the console with Kinect 2 from $499 USD to $399-$449 USD.

Microsoft Xbox One holiday
Microsoft's Xbox One holiday price cut to $349 USD could become permanent.

What's even more intriguing is the mention of a second APU upgrade.  Will that bring another die shrink (e.g. TSMC's pending 14 nm FinFET process)?  Will it bring a performance upgrade?

Sources: LinkedIn [no cache available], "Mosen" on Beyond3D Forums, EuroGamer





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