Just my guess. The 64kb VRAM isn't enough to hold all the graphic (animation) patterns of both players at the same time (unless both of them are of the same form), and the meager 64kb buffer RAM isn't enough to hold much more stuff for switching into VRAM in real time. This could be seen by the constant interruption from disc accesses though out each stage, and that whenever the player evolves there is disc access. That means there is simply not enough memory to hold data for a single stage plus all the players' transformations. (If this is correct, if you want to have simultaneous 2-P action and do not want to sacrifice animation details, when say P1 is in human form and P2 is a beast the game may pause for disc access even when of of them is just
throwing a punch, which is unbearable). The Hucard version probably changes the graphic patterns in VRAM continuously, but with ROM bank-switching instead of disc access to load data from, so this is much more manageable. I remember someone pointed out that there are differences in the backgrounds of the two versions, and I suspect that the details in the backgrounds are simplified in the CD version too.
Some other games available on both platforms do show traces of this too. As shown in the comparison thread here (or the compiled pages), the CD version of Daisenpuu obviously has
simpler graphics compared to the card release. (And I remember someone mentioned Giant Bonk in the CD version of Book 3 lacks some frames, and that's a SCD game even.)
I don't know, it may also be due to (
Nova, the developer hired by) NEC Avenue's inexperience when working on early titles. Better organisation of resources and compression may help stuff more err.... stuff into memory at one time and could improve the game. There are CD games (i.e. not SCD yet) that at least
seem to be able to load a lot of stuff at one time (or just too well organised that the disc accesses are not noticeable), like Ys I+II, Ys III and the Compile CD shooters. (The original Ranma game, while considered Kusoge by many, is also amazing in this part as well. It has a lot of in-game voices, parallax scrolling and large animated cutscenes that aren't infected by disc accesses like Valis IV.)
No matter what, the developers of the original CD system probably weren't very clear on what to do at the time. 64kb buffer RAM is not enough for anything serious(even the FDS has 32kb). They thought the media could be loaded in from time to time, and some could even be streamed (such as audio). But the drawback is that constant disc accesses are annoying (even more so as it's a 1X drive) and would rid a game of (awesome) redback audio if there are frequent reads within a stage. The SCD upgrade corrects much of this by giving 4 times as much RAM, only that, IMO, this amount of RAM should be there since the original system was released.
Anyway, I think it's a wrong idea in releasing the CD version of the game, as instead of demonstrating the power of the system it just shows its shortcomings. The Hucard version isn't great either, as it lacks the hilarious voice acting, which are
essential for making this otherwise bland game enjoyable (even the Arcade version), and even that the backgrounds of this version isn't better than the Mega Drive version either. Accounted for all the factors, neither version on the PCE could top the MD one. Though the MD version has a lot of stuff scaled down (mostly graphic details, like animation frames, pseudo scaling of sprites and not graying out the screen at boss fight, but that last one could be regarded as a plus, as personally I like the screen to be more colourful), it has a better presentation (with the voices and the bonus parallax backgrounds) and plays much smoother (no disc access, has 2-P coop, controls better too, especially for not requiring to press UP for jumping) so the MD version just wins here.
At least the game is slightly more bearable than Golden Axe.Oh. Back to topic! I never knew there was a fixed version of the game either. There were actually A LOT of new copies here BiTD, and I think I bought it for HK$80 (~US$10). Too bad it's the faulty version (the fixed version is probably VERY rare) and I have a PCE Duo instead of the original system. OOPS!
