[Arm-netbook] EOMA68-A20 schematics review - enable verified boot ???

[Luke Kenneth Casson Leighton]

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


On Thu, Aug 18, 2016 at 9:29 AM, Xavi Drudis Ferran <xdrudis at tinet.cat> wrote:
> El Sun, Aug 14, 2016 at 11:14:07PM +0100, Luke Kenneth Casson Leighton deia:
>> ok i need to do a schematic / PCB upgrade to add an extra address line
>> to the current EOMA68-A20 PCB to be able to access 2GB of RAM instead
>> of the current limit of 1GB.  i've looked at the cost of the 2x DDR3
>> x16 RAM ICs and they're nuts: $9 **EACH** whereas 4x DDR3 x8 RAM ICs
>> are $3.95 giving a total of $12 for the 2GB RAM.
>>
>
> I thought the production units were going to be like the existing
> prototype, but since there's a redesign I just thought it might be
> time to add some switch or jumper to enable/disable writing to some
> NAND area or SD or something ?

 no. sorry.  this is already the absolute minimum that i'm prepared to
do, and it's risky enough as it is.  the board is UNBELIEVABLY dense -
there's hardly a single area of the board where routing on TOP, BOTTOM
and internal Layer 3 aren't absolutely stressed to the limit.

> If the NAND eventually becomes too corrupt to boot from it, then the
> computer card can be repurposed to non-verified uses or sold to someone
> who wants such uses. (or the NAND could be socketed enabling repair,
> but that does not seem easy at all).

 it's doable using a BGA Infra-red Solder Station, heats up the board
locally to 230C and that one IC can be taken off easily.  the only
thing you have to watch is to not knock any of the surrounding
components, or heat the board up so much that components on the other
side start to move or fall off.

 l.