[Arm-netbook] HDMI High-Frequency Layout: Recommendations--Taper

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sat Jan 6 06:49:28 GMT 2018

On Sat, Jan 6, 2018 at 6:35 AM, Richard Wilbur <richard.wilbur at gmail.com> wrote:

>> now the only concern is, blasted frickin apple, has sucked world-wide
>> demand not just for the entire supply of 0.1 10 and 100uF capacitors
>> but f*****g DDR3 and eMMC *as well*.
>> i now have to be extremely careful on selecting the right DDR3 RAM
>> ICs... *sigh*.
> So the situation is the chips at the speed you designed for are
> much more expensive while faster ones are cheaper?

 yyup... except it's more complicated than that: insatiable demand for
fulfilling apple apple apple apple apple apple orders is driving
EVERYTHING up as there is only a fixed capacity at the foundries
making DDR RAM.   consequently, all remaining DDR RAM ICs at *ALL*
capacities and sizes are falling behind... consequently prices are
spiralling out of control.

>  So the trick is how to choose a faster chip and integrate successfully into a system running at lower speed than it is specified for?

 yyup.  have to use the 1800mhz 1.5v x8 DDR3 IC, which fortunately
happens to be down-compatible with 667mhz.  the 1.35v DDR3L variant of
the same chip is *not*.

 still, i cannot risk just relying on one possible DDR3 IC, so i will
have to source 1600mhz as well... and also last resort a 2gigabit IC
which will total, qty 4, only 1GBYTE of RAM.

 the budget's fixed... it's just the way it's going to have to be.
make adjustments that fit within the budget, end of story.


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