CRITICAL CORRECTION to [More memory to SPARCstation1]

[Christopher North-Keys]

An innocent user sent me the following, expecting to save money by loading
a 4/390 with 100ns RAMs.  This is not good.  The 4/390's use 40 ns chips.
The poor machine would not be a very happy puppy after such treatment, I
don't think...

|I found this on the Sun system administrator's bulletin board. Basically
|what it says is that we should spec the 4MB memory SIMMs for use on
|the Suns as 100ns access (or better), block (or "page') mode not required,
|9 bits wide, physically mountable on a Sun 4/390 memory board.
|
|| Date:    Thu, 8 Feb 90 10:40:45 EST
|| From:    bob at morningstar.com (Bob Sutterfield)
|| Subject: More memory to SPARCstation1
|
|| From: ks at tut.fi (Syst Kari)
|| Is access-time 100ns enough or should it be faster?
|
|That's fine.
|
| [ text deleted ]

>From the Sun3 and Sun4/SPARC Hardware_Configuration_Guides, November 1989:

	(Cycle time is measured in nanoseconds.)

Table 1-1 (excerpt) Sun-3 Sun-4 and SPARCsystems CPU/Memory Overview
|
|             |----------Sun-3--------| |-Sun-4-| |--------SPARC---------|
|             50  60  80  150  260 470   100 200   1    330    370    390
|MEMORY:
|Err Detect    bp  bp  bp  bp  ECC ECC   par ECC  |--synchronous parity--|
|Cycle Time   270 200 100 270   80  30    70  60   50  |----- 40 ns -----|

I returned the (hopefully accurate) response:

Be sure to purchase memory with cycle times at or below specification for
the target machine.  Plugging in the wrong memory addition would cut the
speed of the machine by a factor of at least two (I believe), effectively
wasting an enormous amount of the purchase price of the machine.  Puttin
100ns memory in a SS 390 would be idiocy.

Note that even the SS1 uses 50 ns memory, rather than 100.


Christopher North-Keys