🚀 go-pugleaf

In article <819765886snz@longley.demon.co.uk>
           David@longley.demon.co.uk "David Longley" writes:

> - PCI Bus Mainboard 486 - AMIBIOS 1994/5
> 
> I  have  just  spent  the evening trying to get  a  new  "PCI  Bus 
> Mainboard 486" motherbaord to work with a new Intel DX4-100 and a 
> 16MB SIMM (no parity). AMIBIOS (c) 1994, creation date July 1995,
> 
> The system started up first of all, but couldn't see the  floppy. 
> From  then  on,  things just got worse. In the  end,  the  system 
> wouldn't boot at all. Power connections are OK, as are the  leads 
> to the system unit, RAM is OK...cabling is OK....
> 
> Has  anyone  got  any experience of this board or  this  kind  of 
> failure?
> 
> How do you clear CMOS RAM? The only thing I can think of is  that 
> I have switched something on like internal cache when there isn't 
> any. Could that account for the observed behaviour of the system?

The  only thing that looks like it *may* have been wrong  is  the 
pin configuration for the clock speed.

The  manual says that JP11,JP12, & JP18 are the CPU  Jumpers  and 
that JP11 is JP11-A JP11-B and JP11-C.

On the board they are set as follows (schematically):

      ISA         PCI           SIMMS


                        |
              |  |  |   |  Pins 1 & 2 on
              |  |  | 
             on on on
             A  B  C   
               JP11    JP12


            CPU            256K Cache


The manual *looks* like it should be A & B off and JP12 2 & 3.

JP11-A JP11-B and and JP11-C on are for 33MHz CPU in the manual
for JP12, 1 & 2 are on for the 40 and 50Mhz CPU (but then JP18 is 
on as well).

As the board came pre-fitted and sold as a DX-100 system I didn't 
think to change anything, and I'm only guessing that a DX4 should 
be set for 25MHz? (Or should they be at 33MHz?)

I've  tried clearing the CMOS by setting the correct jumper,  but 
it makes no difference.
-- 
David Longley