Does the HD7850 have GCN?

[lakedude]

A while back I read this:

http://www.anandtech.com/show/4455/amds-graphics-core-next-preview-amd-architects-for-compute

which talked about a move from VLIW to SIMD vector processing. That move being what makes a GCN a GCN, if I understood correctly.

Then I read this:

http://www.brightsideofnews.com/new...-mix-gcn-with-vliw4--vliw5-architectures.aspx

which says "When it comes to discrete parts, parts with the codename Cape Verde (HD 7500, 7600, and 7700) and Pitcairn (HD 7800), they are all based on the VLIW4 architecture. The "Graphics Core Next" architecture is reserved just for the 7900 Series."

But then I read this:

http://www.anandtech.com/show/5625/...-7850-review-rounding-out-southern-islands/15

which says "With GCN AMD significantly overhauled their architecture in order to improve compute performance" (regarding the 7850 and 7870)

So what is the deal? Is the vector thing the same thing as GCN? Does the 7850 have GCN or SIMD vector thingies?

 

[notty22]

Yes, but it's proportioned different than Tahiti.
http://www.tomshardware.com/reviews/radeon-hd-7970-benchmark-tahiti-gcn,3104.html

Pitcairn has twice the number of CUs, twice the number of ROPs, twice the memory bandwidth, and of particular importance twice as many geometry engines on the frontend. This works out to 1280 SPs among 20 CUs – organized as a doubling Cape Verde’s interesting 4/3/3 configuration – 80 texture units, 32 ROPs, 512KB L2 cache, and a 256-bit memory bus. Compared to Tahiti, Pitcairn still has 12 fewer CUs and as a result less shader and texturing performance along with the narrower memory bus, but it has the same number of ROPs and the same frontend as its bigger brother, which as we’ll see creates some very interesting situations.

​

 

[Red Hawk]

Yes, it is. That article stating the 7800 and 7700 series use VLIW4 was working off of rumors at the time. The 7900, 7800, and 7700 series all use GCN. On laptops, anything designated Radeon HD 7600m series or lower is a rebadged VLIW5 part, usually the same chip as the Radeon HD 6600/6500 series.

 

[lakedude]

Thanks guys!