This was actually the subject of a chat I happened to be in recently. I'll quote the explanation given there because I don't think anyone would object to the knowledge being shared, but do note that this is one person giving an off-the-cuff paraphrase of someone else's explanation and isn't necessarily 100% accurate: I'm not an expert on the topic, so if you want gorier details than that, I suggest you ask on the PC Engine Software Bible forum. For the record, the image captions on that article are: 1. "Pause during the game and input the command below." 2. "Look, the screen's split into two. The left edge of it is cut off." 3. "An enlargement of one of the screens. You can barely make out the message." The main article is largely just saying the same things with more detail. The fact that there are two screens instead of four is obviously a discrepancy, but it's possible that this specific game is doing additional manipulations with HBlank interrupts to eliminate the lower screens. I have no familiarity with it, though, so I'm afraid all I can do is speculate.