BSD 4_2 development

[unix-history] / usr / doc / hints / 05.t

.sh MEMORY
All VAXes are sold with at least the minimum amount of DEC memory adequate
to run diagnostics.
Additional memory is the lowest risk alternate vendor choice.
We buy the remainder
of our 780 memory from Mostek, National Semiconductor or Trendata.*
.FS
* A list of second
vendors and their phone numbers is given at the end of the document.
.FE
This area is extremely price competitive and there are at least
six possible vendors.
By all means, ask for competitive quotes.
Assure yourself, however, that you are not the first customer for a
new vendor.
.LP
Add in memory for the VAX 750 is a newer item and prices are not as low.
However, this memory is almost identical to the 11/70 MK11 memory and
several vendors have managed to build this product by modifying
their previous 11/70 add-in product.
Trendata also has 1 Mbyte 64K RAM modules for both 750s and 730s.
.LP
Small quantities (one to two megabytes) are usually available off the shelf.
Large quantities (4 megabytes and up)
have taken less than 30 days.
.LP
For the 11/780 memory,
the RAM chips are socketed, and two replacement chips per
board are supplied
by all vendors we mention;
You can pull out the board and replace the
chip at your leisure.
Since single bit errors are corrected this has never involved
any unexpected down time for us.
There is at least a one year return to factory agreement on the boards,
included in the purchase price.
Out of warranty repairs are said to typically cost less than $300.
We have returned only one board to the plant in about
30 board years.
.LP
When purchased from DEC, memory is much more expensive
for any of the machines.
Maintenance on a 1 Megabyte DEC memory module is
$179 per month with
board replacement through field service.  The boards are not socketed.
Delivery times on memory from DEC have typically been substantially
longer than times from second vendors.
.LP
If you are going to have more than
4 megabytes of memory on your 780 you
will need a CPU expansion cabinet
and a second memory controller that includes
a second half-megabyte of DEC memory.
.LP
There are two models of 11/750 memory controllers and backplanes around.
The one currently being manufactured by DEC can be filled with either
quarter Megabyte or full Megabyte modules for a maximum capacity of
8 Megabytes\(dd.
.FS
\(dd It is important when mixing memory module sizes in VAX 11/750s
to install the memory in consecutive slots beginning with the first
and starting with the 1 Mbyte modules.
.FE
The older memory controller and backplane can be populated with only
quarter Megabyte modules for a total capacity of 2 Megabytes.
To make matters even more complicated, 750s exist which
have the newer style backplane and the older controller.
These too will only hold 2 Megabytes of memory.
The smaller capacity system can be upgraded to the larger one, but
this is quite expensive;  check with DEC before buying one, or be sure
that you will be satisfied with a maximum of 2 Megabytes.
.LP