Commander Keen 4 - CGA, Tandy & EGA on a Tandy 1000 TX
11Here I show three versions of Commander Keen 4, two official, one unofficial.
Commander Keen 4 was originally released to support EGA and VGA cards like its predecessors, but this game used a new and more advanced graphics engine. Commander Keen was one of the, if not the first, game to use the hardware capabilities of the EGA to support smooth horizontal and vertical screen scrolling.
While Commander Keen 1-3 were strictly EGA/VGA only, Commander Keen 4-6 and Keen Dreams had separate EGA/VGA and CGA releases. The CGA version lacks smooth scrolling support, the Terminator-inspired intro and the Star-Wars style story scroll. It does support Adlib music/sound effects.
Commander Keen 4's source code is available and people have made several graphics engine ports. The CGA version was converted to use Composite Artifact Color graphics for more colorful graphics.
A Tandy 1000 with its built-in graphics often can look like EGA and shares its 16-color limit when using the standard 320x200 graphics mode. However, the Tandy Graphics Adapter lacks many of the hardware features of the EGA, namely the capability of scrolling smoothly horizontally and vertically. EGA is also programmed very differently to CGA and Tandy graphics. Recently, someone ported the CGA version to use Tandy graphics, so I decided to try it out and see how well it worked on original hardware.
This isn't the first time the game has been modified to work with Tandy graphics, there was an earlier version from an different programmer which used the 160x200 Tandy/PCjr. graphics mode and the composite artifact color conversion as its based. This same author of this Tandy version also did an MCGA version which functions similarly because MCGA lacks EGA features.
The hardware in question is a Tandy 1000 TX with a 8MHz 80286 CPU and 768KiB of RAM. Maximum hard drive speed is provided by an ADP-50L IDE interface and a Compact Flash card.
First I start by showing off the CGA version, then the Tandy version running on the same hardware. The Tandy version has also converted the music to use the Tandy PSG sound chip, in this machine an NCR 8496 (TI SN76496 compatible clone). As the Tandy version was derived from the EGA version, you will not see the Terminator-inspired intro and the Star-Wars style story scroll. For performance reasons it seems that 24 lines on the bottom of the active graphics area are blacked out.
Finally, to complete the comparison, I show the EGA/VGA version running. It is quite possible to get Commander Keen 4's EGA/VGA version running on a Tandy 1000 SX, TX, SL/2, TL/2/3 or RL, all you need to do is to install a discrete EGA or VGA card. I had to capture that separately because I had to shut down the system to add the card, an Everex EV-657B EGA. VSWITCH and ESWITCH allow you to switch between the built in Tandy graphics and a VGA and EGA card, but they only work in an SL or TL or better. I also added an Adlib card so you can get the "best version" on this hardware.
The precision control shown here comes from using a gamepad. Tandy 1000 joysticks are analog, but there is an adapter design to convert them to digital. I made my own adapter, which accepts 9-pin Atari/Sega controllers. So here I am using a 8bitdo M30 2.4g controller.
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