Dear Listers
I have a 486 motherboard as follows: OPTI-895GREEN 486WB. I have the
manual. Currently I am running it with an Intel 486 DX4-100MZ CPU. I
would like to replace the CPU with an AMD AM486 DX4-120 (but at 100MZ).
Thew markings on the chip are - A80486DX4-120NV8T. The chip says 3 volts;
does this mean 3.3 volts?

>From what I can guess in the manual, all the jumper settings are the
same for both CPUs.

Am I correct in this assumption? Can I do any harm if I change some
settings (according to guesses form the manual), as long as I don't
change the voltage form 3.3 to 5?

Joel Bluming
[log in to unmask]

I did a search once through yahoo for OPTi895 and it turned up several
interesting bitmaps of the board and jumper locations for each cpu.
I don't think the jumpers will be the same, although I can't promise
because my bios are pretty old ( I have 4 OPTi895's) and they don't
mention the AMD cpu's.  I do know that the AMD cpu you have is
a write-thru cache model ( NV8T ) as opposed to the faster write-back
cache ( SV8B ) model.  The voltage is 3.3 and your board may be 3.45
like mine, but the difference will not be a problem.  If the existing Intel
cpu is using write-back, and I will guess it does because of the WB on
your board's part number, then you will see a decrease in performance when
you install the AMD cpu.  You will probably need to change a jumper
to tell the board the AMD cpu does not support write-back caching.
Some board manuals list the AMD write-back as an SL-DX4 in the tables
of jumper settings to distinguish it from the write-thru model.
Check your CMOS settings to see if there is a setting for cache and
to verify if it is supporting write-back for the Intel DX4.

You could try http://www.indi.nl/cgi.bin/getjumpers/cgi?14
or just www.indi.nl but the site is in Dutch since it is hosted in The Netherlands.
I haven't tried it because it was an incredibly slow site, although it will be worth
it if it answers your questions.

tom turak