Yea it's the chicken and the egg problem. I was thinking of devices like the 12'' macbook with sholdered ram and pretty much every ultrabook with an intel ulv that has dual channel ram sholdered or in sodimms. I guess the thermal budget issue will become less of a thing when we get to ddr4l On Tue, Mar 14, 2017 at 10:55 AM, Bill Kontos vkontogpls@gmail.com wrote:
The problem right now is that pretty much none of the arm SoC
manufacturers
adds what is needed for supporting a full desktop/ laptop experience, that is more than 4 gb of ram, sata3, general purpose pcie lanes and more
memory
bandwidth for the igpu.
each of those interfaces as hard macros costs around $50k to $100k to license. also the power budget is... well... see below. the licensing cost (and design NREs) for using greater than 4GB of RAM - even if ARM *actually does it* - would be cost-prohibitive.
but the thing is, there's an example SoC that breaks the example that you've given: the rk3288. the rk3288 easily out-performs recent high-end intel atom systems, and can do 4GB of RAM, and is available in a *lot* of very popular chromebooks.
Most of the arm chips right now are stuck at 64 bit ddr4 at most, and the ones we have access too ( being libre) have even
less
bandwidth and are even more limited when it comes to ram.
Just an example, going from single channel to dual channel on an intel
igpu
increases performance by 20-30%, and that's even on a gpu design much
worse
than any powervr or mali gpu.
... with the disadvantage that it increases the power budget (relatively) by an *enormous* amount.
* 32-bit DDR3L @ 800mhz uses around 300mW * 32-bit DDR3L @ 1600mhz uses FOUR TIMES that amount - 1.2 watts. * 64-bit DDR3L @ 1600mhz uses around 2.5 watts
that's just for the RAM ICs, excluding the driver power budget on the SoC itself. a 128-bit channel would be in excess of FIVE watts at 1600mhz.
if you're used to working with SoCs that *don't even need a heat-sink*...
so now you're in to heat-sinks, fans, extra-careful thermal design: now you're in to a $200k design, now you have to *justify* that... and there's no chinese ODM that's going to bother when they can make much more money selling tablets and phones than they can desktops and laptops *with no OS*.
i realise that's a circular trap.
l.
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