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HBM to Revolutionize Video Cards, Starting with AMD's Radeon R9 390X

By: Anthony Garreffa | Editorials in Video Cards | Posted: May 19, 2015 12:00 pm

The Problems With GDDR5


It's funny... that right now, all of the flagship GPUs are based around GDDR5. We have no problem with them, with a single flagship card being more than capable of playing all of today's games at 4K 60FPS... but what about tomorrow's games? You have to take another step back, as it's not just about games - it's just as much about the video cards, and what is happening on them, and inside of them, that matters the most.




GDDR5 takes up a considerable amount of space next to the GPU itself, and these chips are not getting any smaller. The higher the bandwidth, the larger number of devices are required to get there. Board real estate is something that is taken up very quickly by GDDR5, which is something that HBM will solve within its first generation.





Then we have the power demands of GDDR5, which require larger voltage regulators - and again, this is something that HBM will fix with its first generation. Shrinking various parts of technology works, but die stacking is something that is coming in very quickly. We're already seeing the benefits of 3D NAND flash in SSDs, but stacking the RAM on GPUs is going to bring in an entire new beast of GPUs that we, until now, didn't think was possible.




Your next question would be "why not make GDDR5 faster?" AMD answers this quite well in the slide above, where if they were to crank up the speeds of GDDR5, it would not only require more power, but the heat generation is only going to go up, and the amount of talk between the logic chip and the DRAM chips is going to increase. Then we have the issue of the growing amount of framebuffer, with cards like the GeForce GTX Titan X featuring 12GB of GDDR5, we can't continue to 24GB, 36GB, and so on with GDDR5. It's next to impossible without video cards doubling in length.



The Interposer


We've been talking about something called 'The Interposer' more and more with our Radeon R9 390X and R9 490X rumors, but now we can go into much more detail that the NDA on this is up. Integrating as much as you can onto the interposer is something that AMD has been wanting to do for a while, but with HBM it's completely possible.




Where HBM comes in handy, is that the DRAM itself can be pulled in much closer to the logic die - as close as technologically possible right now. By shortening the space between the DRAM and logic die, it enables massively wide bus widths - with the Radeon R9 390X rumored to feature a 4096-bit wide memory bus, up from the 512-bit memory bus on the Radeon R9 290X.


Improving the proximity also greatly simplifies communication and clocking, as well as the bandwidth-per-watt. It also paves the way for integration of "disparate technologies", such as DRAM. AMD has worked closely with industry partners such as ASE, Amkor and UMC to develop the first high-volume manufacturable interposer solution.

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