VOGONS


First post, by zbiggy

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It looks MCGA is compatible with VGA so dosbox also supports MCGA. However I did not find any informamtion dosbox supports MCGA. Maybe it could be good to add such informaton to supported harware list?

Reply 1 of 7, by Kippesoep

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MCGA and VGA are not strictly compatible. MCGA is a subset of VGA (well, almost). VGA's commonly used (for games) resolution of 320x200 in 256 colours is available on MCGA, though. When games have MCGA support, it's usually a version of this mode, so it also works on VGA.

Reply 2 of 7, by vasyl

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In a sense, VGA emulates MCGA. The emulation is so good that I am not even sure if there is anything that can be done on MCGA that wouldn't work on VGA. The opposite is not true -- so popular ModeX won't work on MCGA.
There were not that many real MCGA adapter in existence. PS/2 Model 25 came with one, I think you could get it for Model 30 (option?) at some point but that's about it. I never heard about MCGA clones.

Reply 3 of 7, by `Moe`

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A friend of mine owned a PS/2 with genuine MCGA. Slow as hell - he played Eye of the Beholder in CGA mode because the game was crawling with MCGA output.

MCGA is somewhere between EGA and VGA - it has 256-color modes from VGA, but not the hi-res 16-color modes from either EGAor VGA. It has CGA compatibility.

Reply 4 of 7, by Servo

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The emulation is so good that I am not even sure if there is anything that can be done on MCGA that wouldn't work on VGA.

correct, VGA implemented the two MCGA modes identically. Most all early VGA games were really just MCGA. DOSBox doesn't "support" MCGA in that if it was truly in MCGA mode, EGA games would fail, mode x games would fail, and so on...

The PS/2 model 25 and 30 both did indeed come with MCGA, though some later versions of the model 30 switched to VGA.

`Moe` wrote:

A friend of mine owned a PS/2 with genuine MCGA. Slow as hell - he played Eye of the Beholder in CGA mode because the game was crawling with MCGA output.

I also had an MCGA machine; 256 color mode was definitely slower than CGA 4 color (as would be expected), but probably a slow processor was the issue here. (the PS/2 25 and 30 both initially came with 8mhz 8086).

Reply 5 of 7, by jal

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zbiggy wrote:

It looks MCGA is compatible with VGA so dosbox also supports MCGA. However I did not find any informamtion dosbox supports MCGA. Maybe it could be good to add such informaton to supported harware list?

DOSbox emulates the MCGA emulation of the VGA. So strictly speaking, it's just a side-effect.

JAL

Reply 6 of 7, by Great Hierophant

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I believe the main differences between VGA and MCGA, when it comes to the modes they have in common is the way they deal with memory. Mode 13h is well-suited to MCGA's linear memory mapping. The VGA uses planar memory, so it must emulate the memory map in hardware.

Also, in another sense DosBox is closer to MCGA than to VGA. The text resolution in DosBox's VGA mode is 640x400, which is what MCGA used (8x16 text box.) Proper VGA used a 720x400 text mode (and a 9x16 text box.)

correct, VGA implemented the two MCGA modes identically. Most all early VGA games were really just MCGA. DOSBox doesn't "support" MCGA in that if it was truly in MCGA mode, EGA games would fail, mode x games would fail, and so on...

The PS/2 model 25 and 30 both did indeed come with MCGA, though some later versions of the model 30 switched to VGA.

Originally, the PS/2 Models 25 and 30 came with MCGA and an 8088 @ 8Mhz. However, both were upgraded to VGA and a 80286 @ 10MHz.