AMD’s Radeon R9 380X ‘Fiji XT’ GPU Die Size and GCN Specification Leaked – Releasing in June 2015
Some very interesting information was posted over at Bitsandchips.it recently. The report states apparent inside information about AMD's upcoming Fiji XT die claiming that it boasts a die size of 550mm². The report also lists other information and concludes with the fact that AMD will be releasing the R9 380X sometime in June, just before Computex 2015.
Fiji XT has a die size of 550mm², rocks GCN 1.2 and HBM, releasing before Computex 2015 - Alleges Italian Report
Let's go step by step over the claims made by the article. First of all, Fiji XT apparently has a die size of 550mm². That is a pretty huge die, considering that Hawaii was around 438mm². However, that still is comfortably away from TSMC's 28nm fabrication limit (which is 600-650mm² depending on the exact process). For those interested, if you remember the die shot analysis of the GM200 I did, I arrived at an answer of 632mm² with a high confidence and error of margin of 2.5%. That equates to ~619mm² on the lower bound. Even if you were to assume a lower confidence and 5% MoE, that equates to ~600mm² on the lower bound - still a larger die than the 550mm² mentioned here.
The second thing mentioned is something we have known and reported for a long time - HBM memory. Unless AMD changes its mind, HBM is definitely on track. It could come as a pure HBM memory standard completely replacing GDDR5 memory or it could come as a a Hybrid memory standard with the HBM acting as buffer. Either way,memory bandwidth issues are about to become non existent. Thirdly they mention that with Fiji AMD should shift to a better, more efficient tiled version of GCN: 1.2. This is the same GCN architecture that appeared on Tonga and should provide a very decent architectural boost. Couple that with over 550mm² of die size above and you have got a very formidable chip.
Now I am fairly confident that the analysis I did would meet atleast the 5% error of margin (or low confidence), so that puts the GM200 core at exactly 50mm² more die area than the Fiji XT GPU at minimum. However, the Fiji XT is actually the R9 380X not the R9 390X. The R9 390X should be called Bermuda XT. I find it very interesting that AMD has left itself a margin to expand on the 28nm process; or could it be that their financial troubles are greater than anticipated? Taping dies is very very expensive, so I don't see the R9 390X arriving any time soon, meaning the Fiji GPU will remain the top tier AMD product for quite some time. The GPU is thought to have 300W TDP (just imagine the performance with that kind of TDP) something I wholeheartedly support on high end GPUs. As you probably already know, AMD will be using a hybrid cooler to cool this monster. It is expected to arrive in June 2015, shortly before Computex, Taipei.