View Full Version : XT & Tandy CM-11 - screen cut off horizontal

December 2nd, 2011, 08:47 PM
I just got an XT with MDA(I think? Chip layout isn't the same as an IBM MDA, but only pushing video on pin 7) & a Tandy CM-11 (black bezel)monitor. I've wired up an adapter (pin 7 MDA -> 3,4,5 Monitor) and I'm getting video out, but part of the screen is cut off on the left.
The H-center on the monitor is adjusted as far as it will go, turning it in the opposite direction pushes the screen farther off. Does anyone have any suggestions on how to fix this? Thanks.

December 2nd, 2011, 09:46 PM
According to the Internet, the CM-11 is a CGA monitor. So you are trying to drive a CGA monitor using MDA signals.

Refer http://www.minuszerodegrees.net/mda_cga_ega.htm
MDA and CGA use different horizontal and vertical sync frequencies.

I don't know how flexible the CM-11 is when it comes to the horizontal/vertical sync frequencies, but you could be operating the CM-11 outside of its design limits, and if that's the case, risking damage to the CM-11.

December 3rd, 2011, 07:17 AM
Ok got it, Ill stop using the monitor for the time being then. Is there any way to 'convert' the signals coming out of the MDA to match the signals produced by a CGA card? Or would it be cheaper to just find an 8bit CGA card?

December 3rd, 2011, 12:54 PM
I think CGA card.