Intel is officially not interested in dGPUs.
For now, at least. Might be a natural consequence of scaling up their designs. When you're pumping more money into your drivers, your uarch, your dev relations... it starts making more and more sense. They've got a nice process lead, but they're obviously behind on their architecture.
Larrabee, in part (or mostly?), failed because Intel had a terrible base to scale up from. They historically had poor drivers, poor image quality, poor performance... and suddenly, they wanted to scale the garbage up and expected to be competitive. But they acknowledged that there's huge potential to capture market share in the growing, lucrative HPC market... so we'll see how Knight's Landing looks later this year.
That's for only 128MB also, try putting even a 1GB framebuffer (which, btw, would offer outstanding bandwidth) on eDRAM and you can barely fab the chip. They will have to go to 256MB soon anyway.
I get the whole PCB and power issues but eventually eDRAM will be untenable if they want to really compete with dGPU
Yep. But that's what stacked memory is for. This is an interim solution. AMD was supposed to use GDDR5m for Kaveri, but that didn't happen.
L3 cache is very expensive isn't it? Also, putting extra L3 cache would put the GT4e skus in a weird place of having more cache than the best Xeons (per core). and more cache than their socket 2011 counterparts.
It's 3x more expensive per bit. Undoubtedly that number is lower for equivalent performance, but yeah, it's not cheap.
I think quad channel is really the answer as it also increases CPU performance greatly.
I don't think so. They'll be okay for now with eDRAM. With Skylake, they'll get DDR4, which will hold them over until stacked memory comes down in price to be able to use it.
This eDRAM will never achieve performance parity with 512 bit GDDR5 and better interfaces that dGPUs have today. It offers more bandwidth but at the cost of not having nearly enough frame buffer.
eDRAM gets really close, actually.
Iris Pro:
25.6GB/s (DDR3) + 50GB/s (eDRAM) = 75.6 GB/s
GT 650M:
80.3 GB/s
Of course with Haswell, the CPU uses that bandwidth too, but the gap still isn't that large.
Intel actually claims the following:
It would take a 100 - 130GB/s GDDR memory interface to deliver similar effective performance to Crystalwell since the latter is a cache.