So some thoughts about possible expansions soc:

Most space is going in for battery so i want a really small form factor. 5.5 x 5.5 cm will fit below camera.

Most problems with soc is powerconsumption. You are limited to <1 watt if you want to power it via N900) I may be wrong on this numbers but i meassured something about that on the sd bus and it matched with the max usb host mode values.
working suspend resume!

community support and recent drivers

linux

affordable

Some possible candidates:

intel edison
+x86 browsers
+ kind of powerful compared to n900
octane score 1000
- community unfriendly
you need an break out to do something
closed source parts
kernel 3.14?
- intel
power consumption:
standby min 13 mW (35 mW with wifi)
max <1W



beagle core
+ ti,bbb in small kind of known community
- unknown powerconsumption for core
- powerconsumption for bbb
suspend 0.1W without ethernet and hdmi
(https://e2e.ti.com/support/arm/sitar...f/791/t/374553)
3 hours on idle, 1400 / 3 ~ 500 ma => 1500 mW
(http://www.element14.com/community/c...battery-system)
- ti
octane score 800 (bbb)

rasberry pi zero
+ linux desktop in pocket
- a laggy linux in your pocket?
+ cheap
- too long in size
power consumption:
no standby (=idle)
ide 100ma at 5V = 0.5W = 500mW
(https://github.com/geerlingguy/raspb...er-Consumption or http://raspi.tv/2015/raspberry-pi-ze...r-measurements)

acqua a5
+ i like the openess of that device, it seems very friendly
+ you can get still a linux kernel 4.2 image for the older g25
? 526 mhz a5 maybe slow but 850 dmips is hopefully in the n900 ballpark
and it appears to have a hardware double precission fpu which should be 3 times as fast a8 and has 512mb
- only the version without l2 cache and neon is used on Acqua
+ atmel seems to push upstream
power consumption:
standby 33ma at 3.3V = 100mW
(https://groups.google.com/forum/#!to...ms/x2XbyutjHVA) (sadly no lpddr option witch would reduce power consumption to a 1/3 according to atmel)
ide 100ma at 3.3V = 0.33W = 330mW
max power consumption 500mw
- seems to be slower than even the rasberry pi zero


second n900
+ own battery
+ case
+ great device
- end of life n900 getting rare
- covers camera, maybe another slider
- no dp floating point unit
- recent kernel with power management is thankfully(!) worked on
but slowly
power consumption on kernel 2.6:
https://wiki.maemo.org/N900_Hardware_Power_Consumption
on 4.2:
6 hours on idle, 1400 / 6 ~ 250 ma => 800 mW
(http://talk.maemo.org/showpost.php?p...87&postcount=8)
suspend unknown

fun candidates:
ga144
+ very powerefficient
+ 144 700 Mhz cpus no floating point on these
+ forth
- maybe missing some memory
- limited io
- browser has yet to be written

The field looks very sparse for mainly a linux/browser on chip
Does anyone know other possible devices, or has experience with the acqua a5 or atmel?

I need to see if n900 supports somehow spi sd cards that would make connecting more easy. But as said in another thread my gsm is gone again. So i have to adress that first before i make improvements.