decserver 550 in Kansas City

From: Jonathan Engdahl <>
Date: Thu Feb 27 23:38:00 2003

Here is the webpage where I tell exactly how to mod the DECserver CPU into
an 11/53.

In short, you have to reburn the ROMs, and solder in a 1K resistor. On the
old (.5 meg) boards, you also have to cut a jumper.

And here is the best example of the result to date (this is the description
page for the system I just eBayed):

Most of the DECserver boards I have found have 1.5 megs of RAM, late
revision CPUs, and 18 MHz cystals. Last week I got one of these for $5 on
eBay. Using a complete rebuild of UNIX as a benchmark, such an 11/53 is only
about 20% slower than an 18 MHz 11/83 with PMI memory. When I "diff -r" two
directory trees, the 11/53 is actually significantly faster.

I drill off the S-box handles, and replace them with a standard latch from
the stock that I got from Ethan. My web page shows how to build the console
cable. I have the user guide for this board. Does someone want to scan this
and put it on the web?

You can drill the handle off a DESQA, install a standard latch, short out
the fuse connector, carefully disassemble the AUI connectors, and replace
the AUI ribbon cable with a longer one. The result is identical to a DELQA.

RQDX3 are cheap and easy to find. The only really difficult part is finding
(large)hard drives. For that, I've figured out how to use other Maxtor
drives (see But even the
substitutes are hard to find.

Jonathan Engdahl
"The things which are seen are temporary,
 but the things which are not seen are eternal."  II Cor. 4:18
----- Original Message -----
From: "McFadden, Mike" <>
To: <>
Sent: Thursday, February 27, 2003 10:35 AM
Subject: decserver 550 in Kansas City
> Wandering through the local surplus I found a decserver 550 in a full
> rack.
> It had the following boards in it.
> 4 X CXA16-M   M3118
> 1 X DESQA-SA  M3127
> 1 X KDJ11-SD  M7554
> Bulkheads, power supply, and cables
> I read somewhere that it could be converted to a 11/53 with a minimal
> effort.  How much trouble?
> Mike
> m m c f a d d e n _at_ c m h . e d u
Received on Thu Feb 27 2003 - 23:38:00 GMT

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