Low power SBC with large memory

I've got an application that needs an SBC (a redundant pair, actualy)
which will survive 24 hours on battery power.  I either spec a bank of
big batteries, or find something less hungry than the 12-watt Ampro
board I was originally looking at.

I need Ethernet, 4 RS232 ports, USB, and 512MB of DRAM.

I did some searching for Alchemy or XScale SBCs, but everything strikes
out on the memory requirement.

What's the lowest-power big-memory SBC out there?  Thanks.

rich@kastle.com wrote:

> I've got an application that needs an SBC (a redundant pair, actualy)
> which will survive 24 hours on battery power.  I either spec a bank of
> big batteries, or find something less hungry than the 12-watt Ampro
> board I was originally looking at.

> I need Ethernet, 4 RS232 ports, USB, and 512MB of DRAM.

Getting much below those 12 Watts is going to be near enough to
impossible to not be worth trying, I'm afraid.  The problem is the 512
Megs of DRAM.  I don't have hard numbers at hand, but from the
technically oriented reports on laptop PCs I got an impression that
512 MB of DRAM may well eat a good fraction of those 12 Watts all by
itself.

So prepare to bite the bullet and get a serious battery.  12 Watts for
a full day ==> a full-size car battery.  Per SBC.  Or consider a UPS
system with higher energy density than a lead-acid accumulator.  Fuel
cells look promising on that front.

> What's the lowest-power big-memory SBC out there? 

You may already be looking at it.

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

rich@kastle.com wrote:
> I've got an application that needs an SBC (a redundant pair, actualy)
> which will survive 24 hours on battery power.  I either spec a bank of
> big batteries, or find something less hungry than the 12-watt Ampro
> board I was originally looking at.
>
> I need Ethernet, 4 RS232 ports, USB, and 512MB of DRAM.

The geode sbc have ethernet, 1 RS232, 4 USB and 512MB/1G DDR2.
It consumes about 5 watts.  You can use additional USB to RS232
converters.
We are planning to run it from a 12V solar panel ourself.

>
> I did some searching for Alchemy or XScale SBCs, but everything strikes
> out on the memory requirement.
> 
> What's the lowest-power big-memory SBC out there?  Thanks.

rich@kastle.com wrote:

> I've got an application that needs an SBC (a redundant pair, actualy)
> which will survive 24 hours on battery power.  I either spec a bank of
> big batteries, or find something less hungry than the 12-watt Ampro
> board I was originally looking at.
> 
> I need Ethernet, 4 RS232 ports, USB, and 512MB of DRAM.
> 
> I did some searching for Alchemy or XScale SBCs, but everything strikes
> out on the memory requirement.
> 
> What's the lowest-power big-memory SBC out there?  Thanks.
> 

Have a look at the VIA boards in mini-itx form factor.
We had one of them running with 8W including hard disk
with Linux. The same configuration with Win2k took 34W
though. But with an XP embedded the consumption
should come down.

Rene
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
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On 16 Mar 2006 20:24:47 GMT, Hans-Bernhard Broeker
<broeker@physik.rwth-aachen.de> wrote:

>rich@kastle.com wrote:
>
>> I've got an application that needs an SBC (a redundant pair, actualy)
>> which will survive 24 hours on battery power.  I either spec a bank of
>> big batteries, or find something less hungry than the 12-watt Ampro
>> board I was originally looking at.
>
>> I need Ethernet, 4 RS232 ports, USB, and 512MB of DRAM.
>
>Getting much below those 12 Watts is going to be near enough to
>impossible to not be worth trying, I'm afraid.  The problem is the 512
>Megs of DRAM.  I don't have hard numbers at hand, but from the
>technically oriented reports on laptop PCs I got an impression that
>512 MB of DRAM may well eat a good fraction of those 12 Watts all by
>itself.

Unless modern DRAMs are really different from old DRAMs, a single
readout will always require writing the whole row back into memory
cells. Thus, the larger number of memory accesses, the larger the
power consumption. 

If the processor sleeps most of the time, the DRAM power consumption
should drop dramatically. Ultimately, the minimum power consumption
depends of the refresh consumption. Thus, some assumptions about the
processor duty cycle should be available, before determining the DRAM
power consumption.

Various DRAM cycles with a single RAS but multiple CAS accesses, will
consume less power, since the CAS only cycles would activate only the
column output selectors after the full row has once been processed by
the sense amplifiers during the RAS cycle.

Paul