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Machiavellian on 03 April 2013
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Machiavellian said:
ethomaz said:

Machiavellian said:

DIfference is one is performing 64 threads while the other is doing 32.  As I stated this is what the poster draws his conclusion that the 12 SC or Shared Cores he likes to called it is actually an Array of 4 CU cores instead of just being one CU core.

No. You are reading wrong... the memory mapping is 64bits not 64 threads and each CU have 64 threads.

VGLeaks just use wrong terms.

- as SMID is CU (in vgleak term)

 - each SMID = 64 thread lockstep (Vgleak term) 
 - each CU : 16 Operation /cycle across 4 ALU = 64 ALU per cycle/lockstep

 - in Vgleak term Thread = ALU
 - in vgleak 1 Operation = 4 Thread

Edit - Fixed.

 

Ok that makes sense.  I just did some more digging and see that vgLeaks is confusing a SIMD with a CU because here is what they say about the PS4 arch in this artical.

 


 

UPDATE: some people is confused about the GPU, here you have more info about it:

Each CU contains dedicated:

- ALU (32 64-bit operations per cycle)

 

 

This is from vgleaks concerning the PS4 GPU specs.  From there statement they are saying that the ALU executes 32 operations per CPU clock cycle.  Which would mean either the CU unit on the PS4 has only 2 SIMD or they were just wrong in their assessment. 

 

 

 

 

 

OK, I am quoting my own post because I wanted to make clear why it seems that vgleaks is confused about what they are saying concerning the Durango SC Unit.  What could be happening here is that their diagram has the wrong terms or names which makes a big difference in how you view this content.
Here is the breakdown of the SC unit in durango from vgleaks

http://www.vgleaks.com/durango-gpu/sc_durango/

If you change the SIMD to CU then you start to understand why this could be a blunder by vgleaks.

Now here is where it gets interesting.  This is the breakdown of the 7970 AMD card, does the diagram look very familiar

http://i.imgur.com/g61Dtdy.jpg

Could it be that the SC or shader cores on the Durango are an array of 4 CUs instead of 4 SIMD.  If so, then the Durango has 48 Cu instead of 12.  Could the Durango actually have a 7970 (actually a little better as the 7970 only has 32 CU).