Manual clearly states it supports up to 128MB of ram. When it says 16M it means 16M x 36bit = 64MB SIMMs
Manual has jumper settings for DX4 with 3x multiplier = 100MHz. Those were only in 3V. Board lacks 3V regulator 😮 WTF is going on?? Is the regulating transistor mounted inside the socket under CPU? Comparing jumper tables it looks like Jumper 16 dual block is responsible for switching between 5 and 3.3V. In theretroweb picture there is an empty 3 pin footprint nearby that could be the missing 3.3V regulator.

Are you sure you correctly set all the jumpers for "DX4 with 3x multiplier" from the manual? page 84 second option
as a last ditch effort set fsb to 25MHz

i think i did there is a voltage regulator on the board next to the cpu socket
the board came with 32mb it works but makes everything even slower \
i wil try again tomorrow and see if i can get the 100mhz to speed up

make sure the ram you use is FPM

i tried all options iam 99% shure 100mhz is not supported 66mhz is max ...the end 😀
iam happy with 50

Considering the photo on theretroweb is not showing a 3v VRM.
Could you post a photo of your mainboard front & back, just the mainboard, no cpu, no memory, no expansion cards?
thanks.

that board 100% supports dx4 100MHz since it has x3 configuration right in the manual
pci version on retroweb has the regulator

rasz_pl wrote on 2023-08-30, 22:05:

that board 100% supports dx4 100MHz since it has x3 configuration right in the manual
pci version on retroweb has the regulator

I'm going off of the link posted in the first entry of the thread.
Likely revisions/releases of same board with slight differences.
VL without vrm, PCI with VRM...

On a photo showing the BIOS settings there are 2 interesting options disabled: hidden refresh & slow refresh.
Enabling these options will likely speed up your computer.
Here: hidden refresh and slow refresh Tiido explains them.

i wil post some pics later the day ,i tried cpu clock 25 gives me black screen wont boot not even bios ,when i set it to 33 i can boot in to bios no problems but wont boot any further
even if i turn of cpu cache < conflict somehow with the turbo function /40/50mhz works but stil super slow
cpu is not getting hot or anything like that jumper jp16 is to change voltage from 3to 5 etc some one added a 10k resistor to the external cache not shure why
i even tried another bios same thing ,tried difrent cards cables cf card real hdd i changed all jumpers for brand new jumpers ,board has been fully cleaned and inspected
iam out of ideas ,i stil think 66mhz is max
wil post some pics later 😀

update got a step further stil freezes when i press turbo button in !

https://youtube.com/shorts/1oe0JDrlQDk?si=_rlMl4rkf6VdZw-6

some more testing https://www.youtube.com/watch?v=4YAHZta0rHM

https://www.youtube.com/watch?v=KvJcw4e16dY

There isnt a bios option that would fix this current situation. Bios can speed/slow down depending on level of tweaking, but not outright make Pc not work unless you overclock ISA bus or set memory timings too fast.
25MHz must work with any Intel CPU, if it doesnt something is wrong with the board.
Was there a battery leak? that could cause broken Turbo, its implemented by keyboard controller near the battery.
Please upload picture of the simm you are using with readable chip markings. Using unsupported EDO might cause this.

10MB/s ram speed looks like board is throttling ram speed in order to slow CPU down in Turbo off mode.

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no sign of corrosion, ram is correct FPM
Last ditch effort - check all jumpers for proper connectivity. Rarely an old jumper can stop conducting while looking just fine.
As an act of desperation you could try moving ram to second slot.
You can also try removing all Cache chips just for a test.

I looked at videos again and your bios string is
40-0B03-428045-00101111-121593-OP802G-H
while https://theretroweb.com/motherboards/s/pcpart … pci-r#downloads has
40-0B02-008045-00101111-121593-OP802G

where did you get your bios? can you back it up and try the one from theretroweb?

weedeewee wrote on 2023-08-30, 19:48:

Considering the photo on theretroweb is not showing a 3v VRM.
Could you post a photo of your mainboard front & back, just the mainboard, no cpu, no memory, no expansion cards?
thanks.

Ok, so from the photos, it's clear there is a vrm onboard, an MIC 29302BT
and the memory module is FPM, siemens HYB514400BJ-60

What way does that 486 mainboard de-turbo?
Older generations changed the clock frequency, but I doubt that was still valid for most 486 mainboards. more likely is disabling cache ?

deturbo is turbo switch on ,i wil change all the jumpers for new once tomorrow ,friend of mine says he is 90% shure the cpu has some kind of damage and or slow external cache
i think the manual is lying and max cpu speed is 66mhz
the bios i did not change thats the original ami bios that came with the pc .i also tried sram modules just to be shure
i wil try the other ram slots ,i did remove the external chache but no change but wil test again tomorrow
is the one i have newer ? 40-0B03-428045-00101111-121593-OP802G-H < maybe one is for pci and one for vlb ?
i dont have a board to test this dx4 100mhz cpu just to be shure its not the cpu .friend says its the cpu .people on discord say its the motherboard
but the dx2 50mhz works perfect 0 problems with turbo on and off

wil keep you guys up to date