AMD: Southern Islands (7*** series) Speculation/ Rumour Thread

[Tchock]

http://www.3dcenter.org/news/die-finalen-spezifikationen-zu-amds-cape-verde-radeon-hd-7750-7770

Interesting... just 640SPs and still quite close to the 6850 (leaky benchies)?

80W doesn't hurt either.


p.s I don't exactly place that much faith in the CU count, especially with the prior leaks at hand, but this does seem to have more of an official leakness to it

 

[AnarchX]

Running the front-end @ 1GHz should be a big help to reach this performance.

If its true, we might consider 2x10 CUs for Pitcairn?

 

[CarstenS]

I'd think the Pitcairn chip has 2x 12 CUs and 1/16th DP-rate. Probably, not all CUs will be enabled though, depending on performance and whether or not they see GK104 in reach with higher clocks/CU counts.

 

[AnarchX]

A 1280SPs Pitcairn XT with a 1GHz front-end, 32 ROPs should be very close to a 1792SPs/32ROPs@800MHz 7950.

 

[Jawed]

A 1280SPs Pitcairn XT with a 1GHz front-end, 32 ROPs should be very close to a 1792SPs/32ROPs@800MHz 7950.

Maybe it has 24 ROPs and 256-bit memory interface?

 

[AnarchX]

256-Bit @<5Gbps for sure, if it is in ~260mm² range.
But it should be 32 ROPs, because Cape Verde is supposed to have 16.

Maybe Tahiti has no hidden CUs, but hidden ROPs?

 

[Jawed]

But it should be 32 ROPs, because Cape Verde is supposed to have 16.

Why?

 

[AnarchX]

Why?

At least doubled CUs und doubled BW. And they did (nearly) the same in Barts compared to Cayman, which should be also considered with its 32 ROPs@900MHz.

Some performance speculation, for usual 1080p 4xMSAA/FXAA:

HD 7950 - 170-180%
HD 6850 - 100%
HD 7770 - 80-90% estimated


If Pitcairn XT doubles the 7770 specs-wise, it could land with some sub-linear scaling at ~150-160%, which puts reference 7950 only at ~10% higher performance.

 

[Jawed]

Cayman had too many as did Barts. That's why 32 ROPs have been matched with 264GB/s in HD7970.

 

[AnarchX]

In some cases Tahiti looks to be limited by this decision.
And why they put 16 ROPs on Cape Verde?

 

[CarstenS]

Maybe because 16 (and 32 respectively for Tahiti) are a perfect match for the rasterizer?

 

[AnarchX]

Maybe because 16 (and 32 respectively for Tahiti) are a perfect match for the rasterizer?

So 32 should be also the perfect match for Pitcairn.

 

[Jawed]

In some cases Tahiti looks to be limited by this decision.

Tahiti looks limited by drivers. We can revisit this subject in 6 months and get a decent understanding.

And why they put 16 ROPs on Cape Verde?

Yep, that looks excessive to me, just like Barts.

But Carsten's point is the clincher and why I'm prolly wrong.

 

[CarstenS]

So 32 should be also the perfect match for Pitcairn.

If Pitcairn had dual graphics engines which 16 rasterized pixels per clock each, 32 ROPs would be a natural fit.

 

[AnarchX]

It looks like AMDs partners mixed up some Cape Verde and Pitcairn data:

- OBR reports that are 1280/1024SPs @128-Bit!!! and 80/60W TDP printed on his 7700 boxes
- the same at OCUK and they were told prices of ~$180 for 7770 and ~$150 for 7750

 

[Lukfi]

You know, Obr always claims to have various unreleased hardware, but he never provides any proof of that. 1280 SP for a chip that's supposed to be under 150 mm²? I have a hard time believing that. Unless Cape Verde is actually not GCN and these are Barts/Cayman shaders. That would more or less fit, not-GCN Cape Verde being roughly double RV740 (which had 640 SP). Except the memory, that seems slow.

 

[Deleted member 13524]

Nah it's all GCN, that's pretty much confirmed.

 

[iMacmatician]

http://verdetrol.com/

Just noticed something.

If you look carefully at the "Check back soon for a stimulating promotional video!" dotted rectangle on the webpage, you can see a very pale ATI logo.

I was under the impression that AMD had stopped using "ATI" stuff when the 6970 launched?

 

[Lukfi]

Oh my god, you're right. I couldn't see it on my LCD though, at least not before fiddling with levels.

 

[fellix]

ATi shall return!