Yes, chipset limit. No difference between 3-3-3 and 2-2-2. Or possibly some of the buses/controllers, since nothing is locked.

You can see I've benched maxmem with tight timings at almost the same freq.

I tried chiller on NB - did not help at all. Volts helped a little.

This is with 4.4V I/O.

Maybe it's the mem controller, but there's no lower divider - only 1:1 and FSB + 33MHz. Second one not available at high FSB though.

Theoretical maximum for this board is 183MHz.

This was the first time I play with KT133(A).

4.4v its 3.3v line from PSU? What PSU is it?

I/O source is from 5V line (stock board allows up to 3.9V from bios), so I did a simple FB mod.

My 3.3V-modded PSU is Fortron 400 PNF and can go higher than 4V, but for this sub I used Seasonic 1000W Platinum.

Yes, it is FSB + PCI. With that "divider" it reaches roughly the same RAM frequency, but on lower FSB.

I have some Qimondas laying around and can try if it could go higher, but I think chipset/pci/agp is not able to go higher.

First thing I tried was to use the modded PSU with higher 3.3V line, but it did not help.

With the FSB + PCI option I could only boot at about 122MHz FSB and it stops at about 133 within windows.

Which is the same SDRAM freq I could reach with 1:1, ~133*1.33

Of course performance at 1:1 is better on these platforms.

At 133MHz FSB PCI/AGP should reset back to normal, but the "extra 33MHz" options is only available up to 122 in bios, then disappears.

Also bios has frequency addition (up to +28). Maximum you can set is 155 + 28 = 183MHz.