eDRAM too expensive

By: Maynard Handley (name99.delete@this.name99.org), January 14, 2019 4:40 pm
Room: Moderated Discussions
Dan Fay (daniel.fay.delete@this.gmail.com) on January 14, 2019 2:16 pm wrote:
> Maynard Handley (name99.delete@this.name99.org) on January 14, 201
> > > It's not about "10% higher cost than SRAMs" because eDRAM
> > > is denser. It simply adds layers and steps that are
> > > only needed for eDRAM and increase the cost of the whole wafer. If your die would've been 80% SRAM then the
> > > smaller dies with eDRAM might very well be cheaper. But saving 5 mm² on a 100+ mm² die is a net loss.
> >
> > This is not answering the question, it's simply repeating what David said, in a louder voice.
> >
> > HOW MANY ADDITIONAL LAYERS and STEPS?
> > HOW MUCH more expensive?
>
> This is a *really* old article, but IBM estimates here ~20% more:
>
> https://www.edn.com/electronics-news/4336936/IBM-Pushes-eDRAM-as-SRAM-Replacement
>
> They claim here 3 more masks. I don't know if they're "critical layers"
> though. If they are, you might have to double or quadruple that number.
>
>

But that's kinda my point. Articles like that refer to a reality so different from today that it's impossible (IMHO) to generalize from them. If all it takes is still (and who knows whether this is even CLOSE to true) is three extra masks and a few extra steps, to create the deep trench, what could have been 20% extra costs (not what I would have called "incredibly expensive" even then) might be lost in the noise of today's almost 100 masks and almost one thousand steps.

I don't want to harp on the "incredibly expensive" because I'm a dick (though perhaps I am...) but because all too often people make wild claims about cost that are just not that important when looked at closely. A 20% higher cost IS higher, yes, and it matters if you're selling into a commodity market that is buying based on price. But it's NOT a big deal if you're selling into a market that is buying based on something other than price, or packaged into something much larger.
Apple doesn't REALLY care if they can add 20% in cost to the A13, but thereby acquire some sort of unique (or at least impressive) advantage for iPhones, whether it's new functionality (better computational photography than Pixel?) or much better battery life. And $10 more in the cost of an A13 can be lost in the overall cost of an iPhone.

As for AMD, well, that depends on the extent to which they can deliver (and market) a singular product. IF they could use a huge L4 either to get better-than-Intel-level energy in mobile, or better-than-Intel-level single threaded performance, they could charge Intel-level prices. It's clearly harder for them than for Apple; so everything depends on the precise numbers --- how much does cost go up, how much does performance go up, how much does energy go down.

My guess is it IS overall a win, even for AMD's space. But it DOES require a redesign of the system, not just the sort of minor tweak that this year's product appears to be (ie a tock - new micro-arch, rather than a tick - new process).
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                eDRAM too expensiveRicardo B2019/01/14 12:06 PM
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                  eDRAM too expensiveAdrian2019/01/14 01:44 PM
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              eDRAM too expensiveMaynard Handley2019/01/14 11:38 AM
                eDRAM too expensiveanon2019/01/14 02:00 PM
                  eDRAM too expensiveMaynard Handley2019/01/14 02:43 PM
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                      eDRAM too expensiveMaynard Handley2019/01/14 04:40 PM
                        eDRAM too expensiveDan Fay2019/01/14 05:58 PM
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                      AMD CPU die size & functionalityJan Olšan2019/01/16 08:11 AM
                  AMD IO die size & functionalityMaynard Handley2019/01/16 10:17 AM
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