Configure the board for the 66MHz DX-2, then set the FSB to 33MHz (FSB jumper settings are printed on the PCB). The board can run anything form 25 (25x1) to 200MHz (50x4*), including your 80MHz DX2.

*only on AMD and Cyrix CPUs that interpret 2x as 4x internally.

You need to set the processor as DX or DX2.

40Mhz bus speed with 2x muliplier..

Have you find this manual:

ftp://ftp.fic.com.tw/motherboard/manual/486/486-vip-io/

kanecvr wrote:

Configure the board for the 66MHz DX-2, then set the FSB to 33MHz (FSB jumper settings are printed on the PCB). The board can run anything form 25 (25x1) to 200MHz (50x4*), including your 80MHz DX2.

*only on AMD and Cyrix CPUs that interpret 2x as 4x internally.

Basically as an AMD486 dx2 3-volt? Would that not run as an 66mhz then?
Or does the board run this as 80 internally and 33 externally?

EDIT
Is the Resistor, RN20, the one that sets the voltage to 3volt?

Robin4 wrote:

Have you find this manual:

ftp://ftp.fic.com.tw/motherboard/manual/486/486-vip-io/

Yes.
I have downloaded that manual plus the settings from total hardware.
And I have printed them, just to have it by the hand.

brostenen wrote:

Basically as an AMD486 dx2 3-volt? Would that not run as an 66mhz then? Or does the board run this as 80 internally and 33 exter […]
Show full quote

kanecvr wrote:

Configure the board for the 66MHz DX-2, then set the FSB to 33MHz (FSB jumper settings are printed on the PCB). The board can run anything form 25 (25x1) to 200MHz (50x4*), including your 80MHz DX2.

*only on AMD and Cyrix CPUs that interpret 2x as 4x internally.

Basically as an AMD486 dx2 3-volt? Would that not run as an 66mhz then?
Or does the board run this as 80 internally and 33 externally?

EDIT
Is the Resistor, RN20, the one that sets the voltage to 3volt?

You set the voltage to 3.3v or 3.45v (not 3v). I know it has 3v printed on the chip, but I don't think any socket 3 boards can do 3v - only 3.3 and 3.45, so set for one of those. Your best bet is to set ALL jumpers the same as for the 3.3v AMD DX2-66, then set the FSB to 40MHz. That will get you 2x40MHz=80MHz @ 3.3v

I don't think RN20 sets the voltage - if I remember correctly, there's a series of jumpers near a square 3 legged transistor above the CPU socket that are used to set voltage.

Ahhh.... I see.
I have set the jumpers to Amd dx2-80, yet the CPU is detected as an AMD dx4-120 mhz.
Crosschecked the jumpers again, and they are correctly set up.

... you set the multiplier to 3x.... so it's set up for a DX4 - 100, and with 40MHz fsb you get 120MHz... you need to have it set to 2x. Alternatively set the FSB to 33MHz and you will get 100Mhz. It should be stable since 70-80% of DX2-80 are actually rebranded DX4-100 cpus.

The multiplier jumper (J27) is set to 2-3. So it should be running at 2x

Basically this means that the CPU is a DX4-120?

No, it means the multiplier is most likely set to 3x. It would be a good idea to check clock speed in speedsys and cachecheck or PCconfig - it's possible the bios is incorectly identifying the CPU. If they read 120Mhz or the machine freezes, set J27 to 1-2 or remove it completely until you get 2x40. Sometimes jumpers are incorrectly represented in manuals, or differ from revision to revision. The CPU itself has no way of setting it's own parameters like modern CPUs, so it runs on what you set it to run on.

Solved....

It was not the multiplier. When changing J27, the board get confused, and after some swapping around with no change to actual speed. The board simply refuses to boot until I have installed and run the 5x86-133 correctly.

What was the source of the board not recognicing the Amd 486dx2-80, was the voltage regulator. I had to set the voltage regulator to 3.45 volt instead. Then it would first run as an 66mhz, and then I changed it to 40. Tested it through with 4 levels of Doom and 2 times Superscape.

brostenen wrote:

Solved....

It was not the multiplier. When changing J27, the board get confused, and after some swapping around with no change to actual speed. The board simply refuses to boot until I have installed and run the 5x86-133 correctly.

What was the source of the board not recognicing the Amd 486dx2-80, was the voltage regulator. I had to set the voltage regulator to 3.45 volt instead. Then it would first run as an 66mhz, and then I changed it to 40. Tested it through with 4 levels of Doom and 2 times Superscape.

glad you figured it out 😀