🚀 go-pugleaf

I'm not certain, but it sounds like I may have the same mboard or a similar
board by the same manufacturer as you.  It's a PCI bus 486 board with
AMI BIOS.  I also bought it with a 486DX4-100Mhz chip, only my chip is
made by Cyrix.

First of all, the DX4-100Mhz chip, contrary to what you think, uses a
33 Mhz board speed.  It may work with a 25Mhz board, but I would guess
that it would be slower.  33Mhz is the speed that Intel "recommends".

Second, the problems you're having sound like the ones I had.
Here's what I did to fix it (it may work for you, it may not, no
warranties express or implied).
Look for some option called "Auto-configuration" and set it to "off" or
"false".  Setting "Auto-configuration" to "on" or "true" set the cache
speed to "high" or "fast" on my board.  Next, find the cache speed setting
and set it to the slowest speed possible.  That fixed my machine so
that it could boot.

In my case, choosing the option "Load BIOS defaults" was a bad mistake
for me.  Among other things, the BIOS defaults turned Auto-configuration
on.  With previous motherboards I've owned, I've always been able to 
"Load BIOS defaults" and have things work when I got into trouble.
However, with this motherboard, I got into worse trouble.  I talked with 
a couple other people, and they said that indeed, loading BIOS defaults
is not a wise thing to do unless you write down _all_ your current settings
before loading the BIOS defaults.  

A general rule I have followed when messing with BIOS is to only change
one thing at a time.  However even this isn't completely safe;  
in the case of turning "Auto-configuration" to "on" on my motherboard,
other settings were changed, and they weren't corrected by simply reversing
the Auto-configuration setting.

				Scott Miller

David Longley <David@longley.demon.co.uk> 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