[rescue] SparcEngine 20 / Aries Marixx SS MBUS Speed

[Curtis H. Wilbar Jr.]

OK, this one really has me irritated....

I have an Aries Marixx SS motherboard (a Sun Microelectronics SparcEngine 20
board) mounted in a Sparcstation 10 chassis.

It is a working board, with a Sparc 20 VSIMM installed.

Here's the irritating part....

The board is capable of 50Mhz MBUS speed....

The manual states:

"J 1401, J1403, and J1404 are used to select the main clock speed for the
Marixx SS motheboard.  There are two crystal oscillators soldered on the
motherboard, one is used to provide a standard 50 MHz clock signal, and
the other alternate crystal oscillator may provide a different speed.  At the
publication time of this manual, most Marixx SS motherboards provide a
alternate clock speed of 40 MHz.

The MBus processor modules may have their own clock circuit and be
independant of the clock frequency running on the motherboard.

The default configuration is set to 50 MHz.

To set the main clock speed at 40 MHz, install jumper J1401 and set the
jumpers of J1403 and J1404 respectively, as shown in Figure B-3.

To set the main clock speed at 50 MHz, leave jumper J1401 open and
install jumpers of J1403, and J1404 respectively, as shown in Figure B-3."

Then Figure B-3 has two pictures... (a) and (b).
(a) is "Setting the Clock to 40 MHz (Default)"
(b) is "Setting the Clock to 50 MHz"

The default label is in contrary to the paragraph that says the default is
50 MHz.

(a) is J1401 installed, J1404 set to 2-3, and J1403 set to 1-2
(b) is J1401 removed, J1404 set to 1-2, and J1403 set to 2-3

With either setting, using AA2.22.1H or 2.25R ROMs, module-info reports
40 MHz MBUS and 20 MHz SBUS.  Same results with an SM81 or HS166.

So, I'm wondering... is module-info to be trusted ?  Is something wrong with
this board, and it only clocks at 40MHz ?

Hopefully someone out there will have some experience with this board to
be able to shed some light on this situation.

If I can get this thing clocking at 50 MHz, then I've nicknamed it a
SparcStation 15 (half way between a 10 and a 20 :-) although electronically
it is much more of a 20 than a 10).  One notch better than a 10SX, and
the only "drawback" is no internal CD-ROM (which if you have an Aurora 1
chassis is nothing to cry about :-), and uses 50 pin drives (which are not
cheap if you want a decent capacity).

So... anyone have any ideas ?

-- Curt