[Arm-netbook] RAM

[Vincent Legoll]

Hello,

and apologies if this already has been talked about, I tried to find
previous discussions on ML archives, elinux & rhombus sites.

It looks like the DRAM will be standard DDR3, has low power DDR3
been studied ?

Too expensive ?
No available init code ?

I ask because some other ARM boards differentiate themselves
from the other one by using LPDDR3 and that has much better
power consumption characteristics, and so do not heat as much.

The regular DDR3 ones (in certain cases have a heat problem and
have to be down-clocked to operate properly whereas the LP ones
don't...

On the same subject of heat dissipation, some boards use a layer
of the pcb just below the soc to act as a heat spreader by having
a copper area that is not used for signals, and it looks like this is
effective, because other boards that don't have it endure heat
problems.

I had a look at EOMA PCB pictures, but I lack knowledge to definitely
tell if there is such a copper layer provisioned.

Thanks

And Luke, don't overwhelm yourself into burn out.

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Tue, Sep 13, 2016 at 9:31 AM, Vincent Legoll

Post by Vincent Legoll
Hello,
and apologies if this already has been talked about, I tried to find
previous discussions on ML archives, elinux & rhombus sites.
It looks like the DRAM will be standard DDR3, has low power DDR3
been studied ?

i'm not paying someone $10,000 to redo the RAM layout, or spending
6-15 weeks to do the work and have to do multiple revisions because i
get it wrong several times. also i am not sure if the A20 can use
LPDDR3. it can't use DDR3L, i know that.

Post by Vincent Legoll
Too expensive ?
No available init code ?

nobody's using it. 800mhz DDR3 only uses 350mA so it's tolerable.

Post by Vincent Legoll
I ask because some other ARM boards differentiate themselves
from the other one by using LPDDR3 and that has much better
power consumption characteristics, and so do not heat as much.
The regular DDR3 ones (in certain cases have a heat problem and
have to be down-clocked to operate properly whereas the LP ones
don't...
On the same subject of heat dissipation, some boards use a layer
of the pcb just below the soc to act as a heat spreader by having
a copper area that is not used for signals, and it looks like this is
effective, because other boards that don't have it endure heat
problems.

yes. that's in the power layer. it also acts as a voltage reference
stabiliser.

Post by Vincent Legoll
I had a look at EOMA PCB pictures,

there's no such thing as an EOMA PCB. EOMA is an umbrella (class) of
standards. you may be referring to thr specific board which is
designated EOMA68-A20. see standard's (newly-added) glossary on
elinux.org

Post by Vincent Legoll
but I lack knowledge to definitely
tell if there is such a copper layer provisioned.
Thanks
And Luke, don't overwhelm yourself into burn out.
--
Vincent Legoll
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