I believe you only have to set the multiplier to 1x. I seem to recall that those were specifically designed to upgrade old systems where regular DX/2 or DX/4 won't work and which have only 5V as the CPU voltage. I believe the CPU multiplier is fixed internally.

Fun fact, it is actually 3.3V CPU but because of its purpose as an upgrade it comes with an integrated 5V to 3.3V voltage regulator (It's that black device on the top partially hidden by the heatsink).

i will try tonight with 1x but i have my doubts
it runs way hot the black thing burns your finger

what i found strange is that on other motherboards like pcchips i set it at 3x and detected 100mhz correctly..did not try 2x or 1x on pcchips

It's a small heatsink withut a fan... HOT, so maybe you can add a small fan if you're worried.
The multiplier seems to be locked at 3x so you may only be able to control cpu- via fsb-speed.

this overdrive thing is great, the i486 overdrive 100
works right away with the old motherboard detecting it at 100mhz using the 486 dx2 66mhz jumper setting.
i also have a trident VLB videocard.

Some thing i notice, 100mhz is not enough, this motherboard has 256k real cache. And i did notice some slowdowns on doom, specially on big rooms, while on corridors the speed is faster.

i dont remember that happening with a AMDx5 133mhz.
i also need to find out how to make it compatible with an AMD X5 133mhz , the cpu has 4x multiplier, but the manual is so old that there is no info about newer cpus

The AMD 5x86 is a 3.3V CPU, which your motherboard does not support. I think that Evergreen technologies released a 5V version of the CPU but, all they did was to add a voltage regulator in between (similar to what you now have with your Overdrive CPU).
Chances are that your motherboard won't recognise the AMD 5x86, since the BIOS must support it.

You can try to overclock the 486DX4 100 MHz to 120 MHz by setting the FSB to 40 MHz but I would then definitely add a fan on top of the heatsink.
You will then also have to set the VLB jumpers accordingly for >33 MHz operation (this essentially applies a wait state for stability reasons).

Personally, I would leave the CPU stock standard - you risk damaging your CPU.and these CPU's are becoming more scarce.
If Doom runs too slow, use a faster PC or, try a faster VLB graphics card.

Doom is demanding,
if you want more speed you will have to raise the front side bus above 33mhz.
The Am5x86 would most likely be recognized as a DX4 which interprets the 2x multiplier as 4x BUT you would need an interposer or an update processor(e.g. by Evergreen/TI/etc.), which already contains one, to get the appropriate 3.xV voltage.

amadeus777999 wrote:

Doom is demanding,
if you want more speed you will have to raise the front side bus above 33mhz.
The Am5x86 would most likely be recognized as a DX4 which interprets the 2x multiplier as 4x BUT you would need an interposer or an update processor(e.g. by Evergreen/TI/etc.), which already contains one, to get the appropriate 3.xV voltage.

Member Vegge just posted his new Evergreen AMD 5x86 133Mhz in the recently bought this and that thread. I find the Evergreen upgrade a great option and very compatible! It usually is recognized as a "486 DX2 @ 133 MHz" in older 5V only motherboards and can be set to run both 3x or 4x multiplier without motherboard support.

Pabloz wrote:

i also have a trident VLB videocard.

Perhaps upgrading this for a proper video card has more effect than a faster CPU.
I recall back in the day when we had 486DX2-66 systems, that the video card had quite an impact on how smoothly DOOM ran.
A fast VLB card, especially if it can run at zero-waitstate, could make all the difference.
Those Trident VLB cards are barely faster than a decent ISA card, which will bottleneck your game.
You may want to look at an ET4000 or CL542x VLB card, those are fast.

Back in the day, my 486DX2-66 with 0 ws CL5426 VLB card even ran smoother than a friend's new Pentium 60 with some early PCI video card.
Once he upgraded to a Diamond Stealth video card, his system was finally faster than mine.
CPU isn't everything.