Memtest is without errors for both pairs of RAM.
Also, checked timings in Bios, reset CMOS. No success.
Either I am facing some limitation of the memory controller that is integrated in my Winchester CPU.
Also on my ToDo list is to find the data sheets of my modules in order to see if I have to increase RAM voltage.
The 2x512MB pair is Infineon, the new 2x1GB pair is Kingston, both DDR 400 CL3. Will report the entire, lenghty model# if required.
The Winchester core’s memory controller cannot run more than two sticks of memory at full DDR400 speed. You will need to drop your memory speed down to DDR333 speed in order to run stably with four sticks of memory.