Yesterday I checked the 9000/217 98204B combo with my oscilloscope and I can confirm the 25kHz horz. frequency (1V down to 0.3V pulses every 40 us). I cannot measure the pixel clock as my oscilloscope was too cheap (I had to compromise) and thus cannot sample at higher MHz rates. I only see that it goes from 1V to approx. 2.2V. Just for my understanding: if I do the math: 512 pixels x 400 rows = 204'800 pixels at 50 Hz I end up with 10.2 MHz and at 60 Hz = 12.3 MHz. There is more "room" required for the retrace time, probably another 10% or so? So I understand that the monitor must be capable of ~25 kHz and 10...14 MHz and that I better try before buy. It is difficult to find specs for these HP 9000 video boards. In case it is useful for someone ... my list below is still missing DIO-bus type (1 or 2) and signal frequencies. 98204B Video Board medium resolution (512x390) monochrome for 35721 monitor, DIO-1 98542A Monochrome Video Board medium resolution (512x400) monochrome 98543A Color Video Board medium resolution (512x400) 16 colors 98544B Monochrome Video Board high resolution (1024x768) monochrome 98545A Color Video Board high resolution (1024x768) 16 colors 98546A/B Monochrome Video Board medium resolution (512x390) monochrome alpha/graphics, for 216/217 display compatibility (a pair of cards, compatible with 2136 and 217 displays (512x390, 25x80)) 98547A Color Video Board high resolution (1024x768) 64 colors 98548A Monochrome Video Board high resolution (1280x1024) high performance 98549A Color Video Board high resolution (1280x1024) high performance 98550A Color Video Board high resolution (1280x1024) high performance 98700A Graphics Display Station high resolution (1024x768) 256 colors 98710A Graphics Accelerator optional for 98700A 98720A High Performance Board high resolution (1280x1024) nur HP-UX, requires 98724AA interface and 98784A monitor 98730A High Performance Board high resolution (1280x1024) nur HP-UX 98722 memory upgrade optional for 98720A Martin