I'm certain there is a way to interleave 2 1GB stacks into a single 1024-bit channel, memory has always by its very nature been interleaved. This "dual link interposer" business is totally made up as far as I can tell... unless y'all are trying to talk about merely interleaved memory on the same bus.
The Anandtech write up even explicitly called out that it should be easier to incorporate control logic now that its all on an interposer. GPU would see a 2GB memory pool on that 1024-bit bus, control chip could split it across the two attached stacks (much like PLX bridges for PCIe for example). It's for sure possible.
Now whether AMD actually did this or not is an entirely different issue. The slide seem to imply they designed for 4 GB. It could be that an interleaved design ruins the latency advantage of HBM or any other variety of issues they identified with such a solution. I trust that there would be a reason, even if its just that going to 8 with an interleaved design adds too much cost.
Hynix itself have been overly optimistic because they dreamt of 8 high HBM1 and 16 high HBM2. That has been reduced to half later on in their precentations. A classic issue of new untested technology and manufactoring.
I'm certain there is a way to interleave 2 1GB stacks into a single 1024-bit channel, memory has always by its very nature been interleaved. This "dual link interposer" business is totally made up as far as I can tell... unless y'all are trying to talk about merely interleaved memory on the same bus.
Yes, so?
I believe that would require a redesign of the GPU itself...
I believe that would require a redesign of the GPU itself...
I'm certain that the HBM1 standard is publicly available, and has no single word on clamshell-like thingy. Let alone the fact that 1024-bit interface is comprised of eight 128-bit channels. Moreover, that's not really interleaving but more of "share command bus but split DQ".
well, some of them wants to keep the card for 3 years. I could understand that. 0.12% of gamers are 4k. if I am a 4k gamer I would not want a 4gb card either, especially if the price is 700 to 800$ I can understand this too.I find it weird that so many are already sing 4GB wont be enough. Wait until the reviews come out. If the card can do what you want, great, if not, skip it. Why would anyone want to skip a card because of a spec that may or may not be a limit?
idk I'm confident in AMD's ability to optimize their memory usage like Macri said they did.
I dont see the issue with 4GB anyway. 1-1½year down the road when 16/14nm hits, its upgrade time again.
I believe that would require a redesign of the GPU itself...
Not to mention the memory controller would be huge in comparison.
The publication alleges that the AMD Fiji GPUs are not going to form the flagship models of the Radeon R9 390X series, rather form their own separate niche of ultra high end, luxury products from AMD. Basically, the Titan-equivalent of Radeon.
I dont see the issue with 4GB anyway. 1-1½year down the road when 16/14nm hits, its upgrade time again.
These are expected to be 28nm?
AMD's CTO, Joe Macri, explained the 4GB limitation to Ars in a telephone call:
"You're not limited in this world to any number of stacks, but from a capacity point of view, this generation-one HBM, each DRAM is a two-gigabit DRAM, so yeah, if you have four stacks you're limited to four gigabytes. You could build things with more stacks, you could build things with less stacks. Capacity of the frame buffer is just one of our concerns. There are many things you can do to utilise that capacity better. So if you have four stacks you're limited to four gigabytes, but we don't really view that as a performance limitation from an AMD perspective."
"If you actually look at frame buffers and how efficient they are and how efficient the drivers are at managing capacities across the resolutions, you'll find that there's a lot that can be done. We do not see 4GB as a limitation that would cause performance bottlenecks. We just need to do a better job managing the capacities. We were getting free capacity, because with GDDR5 in order to get more bandwidth we needed to make the memory system wider, so the capacities were increasing. As engineers, we always focus on where the bottleneck is. If you're getting capacity, you don't put as much effort into better utilising that capacity. 4GB is more than sufficient. We've had to go do a little bit of investment in order to better utilise the frame buffer, but we're not really seeing a frame buffer capacity problem. You'll be blown away by how much capacity is wasted."
From ArsTechnica:
http://arstechnica.com/information-...hbm-why-amds-high-bandwidth-memory-matters/2/
"we're not really seeing a frame buffer capacity problem. You'll be blown away by how much capacity is wasted"