> > I'm really glad to see another new working LD game in MAME. I noticed when you go
> to
> > the trader to buy time reversal cubes, even if you have the cube limit set in the
> dip
> > switches, you can spam the coin button and get a ton of them. Is this just how the
> > game is or maybe a bug?
> >
> > Btw, if you look in the ROM with a hex editor, you'll find a ton of C compiler
> > related strings.
>
> Maybe it's limited by a coin lockout mechanism, that would be unconventional (usually
> they're just to lock out during boot and at the game's credit limit) but it limit how
> many credits you can put in if they've decided to do it this way.
I have a strong suspicion that Time Traveler didn't have any enforced lockout, and simply didn't expect the user to be able to ram coins into the machine that fast.
Part of my suspicion is because even with the DIP switch set to a limit of 6 rather than 36, the default value of 1 coin / 2 cubes lets you exceed that limit (having a total of 7 cubes) if you don't use your one cube in 1873, and then put 3 coins in at the Trader.
The other part is that the hardware just plain doesn't have that much I/O to sling around.
There are 2 i8255 port expanders, with 3 8-bit ports each. The first group has nothing but inputs on Port A and B, and uses Port C for outputs.
It never writes anything to bits 0..2 or 7 of Port C. Bits 3 through 5 are known.
On the second i8255, all three ports are occupied by DIP switches.
On the 80188 CPU, Timer 0 Out is used for the 1-bit beeper.
If there's a lockout, then as far as options for I/O goes, that leaves bit 6 of Port C on the first i8255, and Timer 1 Out.
Timer 1 Out seems to ride high the entire time, so that rules that out.
Bit 6 of Port C does get twiddled when the user puts coins in during attract mode: It idles high, then the game bounces it low and back to high for each coin. During the Trader sequence, it remains idle until after the sequence is over, at which point it pulses it low->high for each coin that the user put in.
As best I can figure, bit 6 probably advances some sort of mechanical counter in the coin door for book-keeping purposes (even though the game tracks it internally as well), but there are absolutely no outbound signals that flip when the Trader sequence hits the cube limit. When the user is below the limit, the game resets the countdown timer to 14 seconds for each coin that's inserted, and once the limit is hit, it is forced down to 2 seconds. With that in mind, I expect the developers simply figured the user wouldn't be able to get another coin in within that remaining 2 seconds.
Time Traveler is absolutely riddled with this sort of jank, to to be honest: There's a sequence in the 1998 "Era" where you have to repeatedly shoot a zombie-type enemy about 10 times before it goes down. After each shot, both the video and the audio seem to jump backwards a little, making the whole thing look horrendously glitchy. My guess is that due to the width of the playfield and the fact that the actor was holding a revolver, the actor (Stephen Wilber) couldn't mime the 10 or so shots fast enough if the zombie's actor was closing the distance fast enough to look threatening.
I've looked at the footage on the disc itself, and the sort of jumping-back of the footage was mastered directly onto the disc, it's not a glitch. It can't be a read-out issue, because the frame indices in the VBI lines are consistently sequential across the entire thing. Not only that, I actually managed to track down footage of YouTube where someone was lucky enough to hit that scene on a real machine, and it looks exactly as awful and glitchy as it does in MAME.
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