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A PC specification
Build
2006112507 is the result of a 12 month major implementation of the product on a new fleet of
patrol boats comprising 4 x 12 metre, 6 x 16
metre, 2 x 22 metre and (in development) 1 x 28-30
metre.
One
of the elements of this implementation was a concerted
effort to design and supply on-board PCs that truly
suited the application.
While we have
never done such an exercise before we did have
something like a decade of experience observing others
implement the product on all manner of on-board PCs
including "data bricks" (too hot, no grunt, limited
I/O), "tuff books" (limited I/O, limited start/stop
capabilities) and miscellaneous desktop PCs (power
supply issues, limited start/stop capabilities, fragile,
space consuming).
A primary
customer requirement was that the system was to be
automatically started when either ignition key was
turned on and automatically stopped when both ignition
keys were turned off. This was dictated by previous
experience (frustration?) with implementations that
required the vessel operator to manually turn the system
on and off.
To enhance
system longevity a self imposed requirement was that
orderly shutdown of Windows and the PC was to be
performed when loss of external power occurred.
The major
elements of the puzzle were therefore seen to be:
o
Power:
o
Supply to be either 12 or 24VDC in.
o
Internal battery backup, to facilitate orderly shutdown
when external power loss is detected.
o
Power supply module to signal when external power is
lost.
o
Motherboard:
o
BIOS capable of starting PC when external power is
detected, to facilitate automatic start when ignition
key turned on.
o
Digital I/O ports, to facilitate detection of loss of
external power.
o
High FSB spec, to maximize performance.
o
Avoidance of daughter boards, to minimize the potential
effects of shock and vibration.
o
I/O via physical ports (RS232 and USB 2.0) rather than
via external devices such as RS232 to LAN converters.
o
Watchdog timer, to trigger automatic hardware reset in
event of C_wiz shutdown or freeze or Windows freeze.
o
CPU:
o
At least 1.2GHz clock (Pentium 4 cycles).
o
Maximum L2 cache, to maximize performance.
o
Appropriate speed specs to match motherboard FSB.
o
Low wattage, to reduce heat problems.
o
RAM:
o
1GB, to maximize performance by minimizing paging to
hard disk.
o
Appropriate speed specs to match motherboard FSB.
o
Hard disks:
o
Use of laptop hard disks with high anti-vibration and
anti-shock specs.
o
Extreme shock mounts.
o
Mounted in easily removable trays, to facilitate fast
repair and troubleshooting.
o
Enclosure:
o
To be common to all vessel classes, to facilitate fast
repair and troubleshooting.
o
Positive pressure ventilation, to avoid dust
accumulation.
The
single most difficult element was the power supply and
associated battery backup.
A 146mm x
203mm industrial motherboard was used that has the
following major specifications:
o
Socket 479 base support (Intel Pentium M CPU).
o
Up to 533MHz FSB.
o
2 x DDR266/333 SDRAM sockets, up to 1GB per socket.
o
4 x RS232 + 6 x USB 2.0 I/O ports.
o
4 input + 4 output digital ports.
o
All the other normal ports such as 10/100 Mbps LAN, PS/2
mouse + keyboard, parallel, VGA, speaker, microphone
etc.
o
Display specifications include "Intel GMCH Integrated
Graphics controller", "Integrated AGP 4X 2D/3D engine"
and "shared system memory up to 32MB (DVMT)" - in other
words not brilliant but seems to be more than adequate
for our purposes.
The
motherboard is driven by a 1.7GHz Intel Centrino CPU
(supposedly roughly equivalent to 3 GHz Pentium 4) with
400 MHz FSB and 2MB L2 cache with a 25W power
consumption rating, in conjunction with 1 GB of DDR333
SDRAM.
Initially
the hard disks were mounted in a commercially available
shock mount - essentially just a fairly hard rubber edge
strip. This proved inadequate in the 12 metre class
vessels which can be subjected to substantial pounding
at speed. A simple solution in the form of an edge mount
constructed from open cell foam used for air
conditioning inlet filters solved the problem.
The
enclosure type and width was basically dictated by other
PCs being installed on the larger vessel classes - 19"
rackmount. Enclosure height was dictated by the
dimensions of the largest component - the power supply -
resulting in a "2U" (88mm) height. Enclosure depth was
not a major restraint so one which left some space for
unforeseen expansion was chosen.
Positive
pressure ventilation was achieved by only using inlet
fans - i.e. no exhaust fans.
The rear of
the enclosure was professionally modified with a purpose
built anodized aluminium I/O panel.
If you have
any questions, suggestions or comments please do not
hesitate to
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