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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