[NLRS] 439MHZ Radar

[goverby@charter.net]

Dr. Gerald N. Johnson wrote:
> I think the more recent liquid cooled large computers use silicon oil
> instead of water because of its better dielectric properties and lack of
> corrosion. I'm sure silicon oil doesn't have the heat transfer qualities
> of water (very hard to beat) though. That was a late model Cray, but
> since Cray seems to be out of the market and has been for a while, that
> might give credence to the description as "old." The most recent desktop
> PCs have made a few year old mainframe computer look slow and puny.

Since we apparently don't have any crayons on the list to take the bait, it
falls to the ex-crayons.  So I will...

The Cray 2 and Cray T90 were immersed Fluorinert, made by 3M.  It's got a lot
of uses in electronics, and I once found a web page describing its use as as
an artifical blood plasma replacement.  Google will give you good links for
fluorinert.  I never heard it described as a "silcon oil" but I'm not a
chemist.

The Y-MP/M90,C90,T3D and T3E used fluorinert in a cold plate between boards (2
boards on a cold plate).  When I asked why, I was told that Fluorinert had
good heat transfer properties, and it didn't wreck your computer if you
spilled some on it.

Memory bandwidth on this class of systems is as important as clock speed, and
AMD seems to have learned this.  Memory interconnects are as complex as CPUs;
the Cray vector processors had four paths from the CPU to memory: 2 vector, 1
scalar, 1 scalar + instruction fetch.

Cray was bought, but now they're back.  A few years ago SGI sold off the
"Cray" or vector processor side of the company to Terra Computing who changed
their name to Cray, Inc. (NASDAQ:CRAY).  Their twin cities software
development & marketing office is in Mendota Heights.  Their newest vector
system is the Cray X-1.  It's a new CPU, with an SGI ccNUMA memory
interconnect and a boatload of paths from the CPUs to memory.  The CPUs were
planned to be multi-chip modules.  I believe it's primarily air cooled, with a
closed loop fluorinert system that basicly makes up a heat sink for the
hottest ASICs.

As I understand it, our radar sites are running custom systems based on DSP
chips.

Glen Overby, KC0YIT