26 votes
Accepted

Why does PC video memory base address change depending on video mode?

The history behind the various base addresses is as follows: the area starting at A0000h was set aside for video frame buffers in general (see Who set the 640K limit?) MDA used 4KiB starting at ...
Stephen Kitt's user avatar
14 votes

Why does PC video memory base address change depending on video mode?

TL;DR: Compatibility Before VGA there was MDA, CGA and EGA and it's all about continued support. But Why Different Memory Regions ? Video in the IBM PC is based on video cards bringing their own ...
Raffzahn's user avatar
  • 223k
10 votes
Accepted

Commodore monitor to VGA or HDMI

I have this monitor, which I think is a Commodore 64 monitor. Not really. And especially not for the C64. The screen was manufactured in Taiwan (*1) for/by Philips. It was widely sold as a ...
Raffzahn's user avatar
  • 223k
8 votes
Accepted

Hercules to COM<->USB adapter - is it possible?

Unfortunately, Hercules plug, while being the same DE-9 plug/socket as "small" RS232, is completely electrically incompatible - other than using the same connector type, there is absolutely ...
SF.'s user avatar
  • 7,095
8 votes

Commodore monitor to VGA or HDMI

The monitor shown is a Philips BM7523 which is a 12 inch amber monochrome MDA/Hercules display. The cable shown in your photo ends in a DE-9 plug which is standard for MDA, CGA, and EGA. (VGA uses a ...
snips-n-snails's user avatar
6 votes

Why does PC video memory base address change depending on video mode?

For CGA vs. MDA, the reasoning for using different base adresses is simple and obvious: These two video systems are designed to co-exist for dual-monitor solutions thus each need a unique memory range....
tofro's user avatar
  • 35k
5 votes

Hercules to COM<->USB adapter - is it possible?

If you mean the original Hercules graphics card (picture further up), it had a video port and a parallel printer port. Neither can be connected to a RS-232 serial port in a sensible way. And even if ...
dirkt's user avatar
  • 27.3k
1 vote

Hercules to COM<->USB adapter - is it possible?

The Hercules / MDA plug is indeed the same physical as the RS-232 serial port (although 25 pin serial was also used) but the signals are very different. It's absurdly expensive to use this signal for ...
chx's user avatar
  • 931

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