Well, one obvious solution would be to disable the himem memory testing by editing config.sys:

1DEVICE=C:\DOS\HIMEM.SYS /TESTMEM:OFF

However, this would probably just mitigate the effect, not fix the actual root cause. So, ideally, you should try and identify what is causing this slowdown.

For starters:
1. How much system memory are you running, and do you actually need all of it?
2. Is your system speed in line with what is expected from a DX4-100? (i.e.: running a few of the "usual suspect" benchmarks would be good)
3. Are there any other peripherals in your system that have the potential to cause weird incompatibilities?

oke i think i found my problem 32mb is just to much i tested with 4/8 and 16 mb and 8mb is the sweet spot ,but wierd thing is if i hook up the turbo connector it wont boot in to dos it says no os install etc etc when i remove the turbo switch it works fine turbo switch is not realy needed

iam going to turn landmark
any one knows where i can get the exe files

games run realy slow i did couple of test and it showes l1 is active but games run slow ,when u put a jumper on the turbo switch dos wont load ,i tried with difrent cpus same thing super slow ingame and testing

i did some testing with a 486 100mhz and sx

i did some testing with a 486 100mhz and sx

i did some testing with a 486 100mhz and sx

i did some testing with a 486 100mhz and sx

i made some progress with turbo on and cpu cache off i can boot in to dos but cpu is stil slow

Something is seriously wrong with that system. I've a 286 that gets 18 in Norton and 38MHz in Landmark. Also a 486 DLC 40 which shows 65 in Norton and 167 in Landmark.

Even with the CPU cache disabled you should be way faster.

i agree i have cleaned the motherboard chekked for damage ,so far stil slow after dinner wil chek all jumper settings again

32mb might collide with VLB graphic card if it wants to map its linear buffer at standard 15-16MB window, requires setting in bios
why did you change bios? all troubles might be caused by wrong bios for the board
another option is some jumper mismatch
0.0 seek time tells me you use CF card? might not like faster busclock

i changed bios just for testing see what would happen ! yes iam using a cf card but i also tested with a real HDD same problem
i tested with 4/8 and 16mb ram 16 is to slow booting so 8mb is the sweeet spot
after dinner wil chek the jumpers again
i found out they solderd a 10k smd resistor on 2 legs of the cache not shure why
the test showes i have 256kb of external cache
wil keep you guys up to date

Out of curiosity... can you post a photo of the mainboard and indicate which one of those is the turbo button connector?
edit: nevermind, had another look at the TRW page and found it 😀
and,
speedsys is a nice test. ( n )

problem solved the motherboard does not support 100mhz cpus and more than 16mb of ram !
the person before me installed a dx4 100mhz and 32mb of ram the system worked but superr slow !
now i have installed a 50mhz dx2 thats all i have and 8mb of ram and its fast and stable and the turbo switch is also working perfect
did couple of bench test all good

Will you post a photo, front & back, of the dx4 cpu ?
fyi, a 100MHz cpu is just a triple clocked 33MHz one.
and The manual mentions the mainboard supports 16MB simm modules, both 30 pin & 72 pin as well as dx4 cpu support on both the VL and VL/PCI version.

wel i found the pc with the 100mhz it works but when turbo is active it says no dos installed and acts very strange /when i remove the turbo jumper it works but superr slow !!
but the manual clearly says 66max support

i wil test tomorrow again with the 100mhz

I wouldn't.
your dx4 cpu says 3volt.
I do not see any VRM on your mainboard, nor any option for it, nor any mention of support for 3v cpus in the manual.

edit: the max FSB supported by the mainboard might very well be 66MHz. but the DX4 cpu only has an FSB of 33MHZ, same as a DX2 or a DX running at 33MHz
a DX running at 50MHz has an FSB of 50MHz and might (likely will) cause some annoyances with the use of VLB cards.