Alley Cat IBM PC & PCjr Capture with Borders
11Alley Cat was originally made for the Atari 8-bit computers by Bill Williams and John Harris in 1983 and released by Synapse Software. While a fine game on that platform, Alley Cat had a lot of competition and it is perhaps most well-known by its PC port. IBM published several high quality ports of games originally developed on other platforms during the lifespan of the IBM PC and PCjr. Alley Cat was one of the last of these releases. The company shortened its name to SynSoft when IBM was performing publishing duties.
Alley Cat as designed to run on an IBM PC with a CGA card and optionally supports a joystick. On the surface, the CGA support is not particularly impressive. Only the two BIOS-supported color palettes are used, there is no support for artifact color, more colorful modes or alternate palettes. It has support for the PCjr.'s special music chip for its opening song and can display alternate palette colors during the game but is still limited to four colors on screen at any one time.
One thing you will almost never see in YouTube videos showing off this game is Alley Cat's manipulation of the border color. CGA cards were designed to show a border on the left and right sides of the monitors of the day. This was important so text characters would not be cut off by a monitor's bezel. For similar reasons, the top and bottom of the screen would also have a border as not all monitors provided an external control to adjust the line height.
In the most commonly used CGA graphics mode, 320x200 with four colors, predefined into one of two palettes, the color select register on the card can set the background color to any of the 16 colors CGA can display. When the background color changes, the border color changes as well. There is BIOS support for this feature, which is why it works when Alley Cat is run on an EGA or VGA card. The area outside the active screen area was not always black. DOSBox does not, in its mainline builds, support showing the border color. DOSBox-x may and 86Box does support showing border color changes but for this capture I decided to use original hardware.
For the first part of this video I have brought out my Tandy 1000 SX, running it in slow mode for 4.77MHz 8088 performance. As I am running an original disk image through a Gotek with Flash Floppy firmware, the PCjr. enhancements are unavailable on this system. Then for the second part of this video, I brought out my PCjr and put the Gotek into it. I recorded the RGBI output of each system via an RGB2HDMI connected to a Datapath VisionRGB E1s while watching the game displayed by the SX and PCjr.'s composite video output. The audio output was recorded through the RCA audio output from the SX and PCjr., which is much easier than using alligator clips on a PC or XT. Control was provided with a Tandy Deluxe Joystick and a IBM PCjr. Attachable Joystick. Both captures were upscaled to a proper CGA 5:6 pixel aspect ratio and combined into one video.
The PCjr. gives the prompt "Are you using a TV or an external speaker" whereas the PC does not. This is necessary because the PCjr.'s enhanced sound chip can only be heard by an external speaker. If you respond with N, you will hear the same PC Speaker music played on a PC. The PCjr. is slower than the PC because Alley Cat does not use RAM above the first 128K area but for the most part the game speed is the same as the PC.
Several screens in Alley Cat change border color. The most notable example is inside the Aquarium Room's fish bowl. On this screen, as Freddy swims around, he changes color as he starts to run out of air. He is using the background color, so the borders change colors as he does. If he touches an electric eel, the screen will flash bright white. The background and border flash green during the bonus score screen and red in the Kennel when the dogs give a warning growl. The background and border color changes from black to blue when you grab a gift box and flashes blue when you reach Felicia in the Cupid Room at the end of each round.