5150/5151 Video Card??

Fred Cisin cisin at xenosoft.com
Mon Aug 15 11:25:32 CDT 2016

On Mon, 15 Aug 2016, Alexandre Souza wrote:
> This is a CGA clone.


> It can work with CGA [monitors]

> and Hercules monitors/modes, and
connecting a "hercules" monitor, such as a 5151 to CGA can damage the 

> usually were switched by a program called MONO.COM.

such as:
MOV AX, 0002h     ; Set mode to CGA B&W
Int 10h
Int 20h

MOV AX, 003h     ; Set mode to CGA color
Int 10h
Int 20h

MOV AX, 0007h     ; Set mode to MDA 
Int 10h
Int 20h

They can be shortened a byte by using INT 3, instead of INT 20h, or 
lengthened with MOV AX 4C00h   Int 21h.  But, since each program is going 
to occupy a 512 byte sector, the difference won't matter.

or using MODE.COM:

> I Believe I have some boards like that. Possibly I have the manual and
> disk.

Does THIS particular board handle BOTH CGA and MDA frequencies?
If not, telling him to connect his 5151 or "hercules" monitor, is going to 
cost him a monitor.
If so, telling him to connect his 5151 or "hercules" monitor without the 
right switch settings, is going to cost him a monitor.

5151 and "hercules" (MDA) monitors do not like wrong frequencies.

SERIOUSLY: connecting a 5151 or "hercules" monitor to the wrong signals 
can damage it.

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