Some interesting news has come off the GPU rumor mill, including leaked photos of what’s purportedly the Nvidia GeForce GTX 880. The card is expected to offer up to 8GB of RAM with a 256-bit memory bus and possibly water cooling (though this may only apply to the engineering samples). Interestingly, there’s still a running debate over whether or not the next generation of Maxwell parts is built on 28nm or 20nm technology. Based on what we’ve heard, we’re guessing 28nm — 20nm at TSMC is not ramping well for graphics cards according to our sources, and neither AMD or Nvidia will have new big-core GPUs based on that technology this year.

Videocardz published a side-by-side photo of the three chips, which would seem to confirm the fact that what they call a GM2xx is actually a 28nm chip. The GM2xx GPU shown is almost exactly the same size as the GK110 — far larger than the GK104. Given that Maxwell runs larger than Kepler, this would make sense — the GK107 is 118mm sq, while the GM107 (GTX 750 Ti) is 148mm sq. Based on what we know of Maxwell, this implies that the new core either packs far more cores than the old GTX 680 and GTX 770, or an absolutely enormous L2 cache. When Nvidia built GM107, it boosted the L2 from 256KB to 2MB — an equivalent step up for this core would work out to 4MB of L2.

Take the GK104, add more cores, and octuple the L2 cache and you could easily hit GK110 die sizes on the same 28nm node. Consumer availability is being loosely forecast for Q4 2014, though we’re not standing behind that guesstimate.

AMD’s Tonga

Meanwhile, over in Team Red, we have Tonga, an upcoming refresh of something, but we don’t know what. Seriously, this bit gets confusing. Some websites are saying that Tonga is a refresh of the R9 270X and R9 280, while others report the R9 280 and R9 280X are the actual target. The card is rumored to pack just a 2GB frame buffer (down from 3GB) and a 256-bit memory bus, down from 384-bit. It supposedly offers up to 2048 stream processors, 128 TMUs, and 32 ROPS — just like the R9 280X. Opinions are divided on whether or not the core is a bog standard GCN processor with an emphasis on energy efficiency or some other form of hybrid.

Personally, I’m guessing that Tonga takes all the standard features AMD introduced on Hawaii and Bonaire and scales them down into the lower-end of the R9 family. TrueAudio, the display controller improvements, and the slightly enhanced capabilities of what’s informally referred to as GCN 1.1 are only improvements if they’re actually baked into the entire GPU product line. Did AMD opt to drop the frame buffer and cut the memory bus? It’s certainly possible — but that kind of change would be a bit awkward to introduce without changing model numbers, especially since the R9 280 and R9 280X have always been 3GB cards. Then again, it’s possible that the new Tonga cards will simply be sold as “R9 280 2GB” and will carry lower price tags as a result.

It’s a tad odd for AMD to be doing a refresh this late in GCN’s life cycle without an architectural update, but I’m guessing the company will goose the card’s clock speeds at least a little — Tonga could wind up offering 5% to 10% better performance than the older R9 280 and R9 280X cards, and it wouldn’t be surprising. We know AMD is planning a 20nm follow-up to GCN, but the company has been extremely tight-lipped on the details.

That’s the news from the GPU rumor mill so far this summer — we’ll keep you posted as events change.