According to one of the videos, first generation MSX does not support more than one button joysticks and that is why you cannot jump in King's Valley while carrying an object. But MSX2 does support them!
MSX of course does support 2 buttons and preventing the user from jumping while carrying objects is a gameplay element.
yes it's the ram required.
Regarding the buttons, I more meant that the games themselves didn't use 2 button controllers . It's mentioned in the video description.
These weren't common at the time , well I certainly couldn't find any in in 85 in most shops I visited those. My father worked for philips so we had tons of MSX stuff, but no 2 button controlers 
& those that existed were prohibitively expensive. Anyway, developers weren't keen on including 2 buttons Gameplay mechanics at this point so that's why I mentioned that this was an incidental gameplay mechanic.
Hey, pretty cool series / fun to watch!
I only don't understand why you haven't used the music from the games itself for the King's Valley & Payload reviews?
Quite distracting (for me at least) I'm hearing Usas, and IMO you could just have used the music form the game (the same Usas tune over & over again also gets repetitive (if that was your consideration).. 
), will IMO do the reviews more justice.
Btw: AFAIK the radio in Payload is for receiving traffic info, so you can avoid traffic jams (not sure if this effects the hi-way, or cities/villages..) (I believe the latter though.) It won't give you another tune.. (I reckon kids just made that up / imagined that, but I could be wrong, and perhaps some magic is hidden under some function key or something.. )
Looking forward to a new episode, cheers!
I finally had time to do another episode of MSX Mansion. This time it's on my first MSX2 game ever: Vampire Killer
http://www.youtube.com/watch?v=oDymQDekOLE
Let me know what ye think :)
Hey Ollie, I only now see your reaction to my post. Aprreciated.
I understand your reasoning + I also can be a bit nitpicky myself..
Cool to have another episode! (And righteous so... ;)) (Flat Eric's cousin? ;))
Btw FRS's (sd_snatcher's) dynamic vsync patch is also interesting... (enhances/fixes quite some stuff, including a controls keyb <> joystick inconsistency fix.) (Could have been worth mentioning... ;))
Let me know what ye think
Really like how you describe how you felt when first playing this game, have exacly the same memories. Used to receive one or two Konami games at Christmas and in fact they were lasting almost a year. Darn those were expensive at the time... ah crap, they still are