On Fri, 19 Nov 2004, Dennis Grevenstein wrote:

> >  Yeah.  Don't forget to jumper the motherboard for the 5000 mode.
>  
> What jumper do you mean and why is that necessary?

 It's located in the TC slot 0 area, beneath the option board, if you have
one installed.  It should be open for the 5900 and closed for the 5000.  
Originally it was apparently meant to be a diagnostic jumper, but when the
5900 was engineered, it got redefined.  Its state is visible as bit 15 in
the I/O ASIC's SIR register.

 I know it's used by Ultrix to differentiate between the two systems; it's
quite possible it's used by the firmware as well, but I can't tell for
sure.  It won't hurt to set it correctly anyway.  Barring this setting,
there is actually no way to differ the two systems by software means.

  Maciej