[SunRescue] axil 220 and hello n stuff

[=?iso-8859-1?q?kebabthesheep?=kebabthesheep at yahoo.com]

--- Ken Hansen <n2vip at bellatlantic.net> wrote: 
> > > As you know, they have two "stacked" sbus slots,
> I suspect that heat disipation was the motivation -
> rather than create a
> very small area above the SBUS cards with limited
> air flow, by stacking the
> cards they could possibly get better air flow...
> (those big areas on each
> side with all those side vents lead to good airflow)

But, surely stacked cards lead to pockets of trapped -
i.e. execessively heated air -> overheating ?  It
would be better, to just have one long card - it has
the same effective dissipating surface area, just
doesn't trap so much.  The big holes in the case I
suspect do help cooling :)  As do the dual cooling
fans on the side of the case.

> Another thought would be the impact on the
> motherboard area - they would
> have lost more circuit area to the second connector,

True.  But look at the IPX - it is REALLY quite
integrated, but still manages two sbus slots,
side-by-side!  There isn't _that_ much on the axil's
motherboard anyway - its mainly done by a few large
asics.  

One afterthought - stacking the connectors allows one
to directly route the signals togeather - i.e.
corresponding pins on each connector can be (almost)
connected by a straight line, rather than having to
use a two layer structure with vias (one layer to do
the forwards/backward connections and one the do the
sideways), like you would if they were side-by-side. 
Thus a gain in board space has been achieved.  I
suspect this was the point rather than anything else.

> Also, there are not that many "modern" SBUS cards
> that are doublewide, so
> the limitation was considered slight, I'd guess...

Good point.  Especially as sun would encourage
designers to make thier clones incompatible with old
'obsolete' cards.  They were never very keen on people
reusing stuff.  Things look bleak for axil, anyway,
since Hitachi closed down the company some time ago :(

Dave.  

Who just found the unix dumping room at work.  Full of
HP apollos, Vax servers, and a _lurvely_ vax crate :) 
All I gotta do is wait for the relevent bloke to come
back off holiday...

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