What specifically does the Arcade card add?

[soop]

AFAIK, the Arcade cards don't add more sprite capability or more colours, it's just a bit more RAM - so what difference does the RAM make?

[spenoza]

A HUGE difference. RAM is one of the most important commodities to any system. Keep in mind that the PC Engine is actually a bit RAM starved. It has very little work RAM, and at least when running HuCards it primarily has access to Read Only Memory (the HuCard) for most of its data. With CD Rom titles not only does it use the system card RAM as a cache for data from the CD, it can also use that RAM as scratch RAM, since it is read/write. So SuperCD and ArcadeCD games have enough RAM available that the system has a decent sized cache of data from the CD and some space to do its own fiddling in. Regular CD-ROM games have a small enough RAM pool that in order to expand your working RAM space you have to lose a significant portion of your game data cache.

I'm sure Arkhan or Bonknuts or Old Man will correct me where I'm wrong. Hopefully politely  ; )

[soop]

So the data gets read from the CD into RAM, which means less loading and/or more animations and background tiles?

[Arkhan]

Yeah, basically.

Sapphire is a good example.  Look at all those 3D-pre-rendered sprites.  Without enough room to stuff those in, you'd be hosed.  Constant loading/dicking around.   

A standalone HuCard, while starved for RAM, is not exactly limited.  You can load from card faster than from CD. 

There are tradeoffs to each type of media.

[turbokon]

But the games has to be coded to take adavantage of it, otherwise the extra ram doesn't do anything.

[soop]

No-one has ever made a Super CD Supergrafx game - let alone an Arcade Super Grafx game.  SGX is awesome.

[Black Tiger]

Each System card/CD format is basically a cart size.

CD2 = 0.5 meg cart
SCD = 2 meg cart
ACD = 18 meg cart

Since only so much of a game can fit into the space each format supports, normally only a stage or a boss is used per load. The Arcade Card is so huge though, that entire Genesis or SNES cart games could fit into a single load. Instead, ACD games tend to pack in content proportionate to a Neo Geo sized cart into a single stage, match, etc.

[SignOfZeta]

So the data gets read from the CD into RAM, which means less loading and/or more animations and background tiles?

It usually means much MORE loading time since the speed of the CD, CPU, bus, etc don't change. If a garden hose can fill a gallon jug in 5 seconds, it will take 50 seconds to fill a 50 gallon barrel. Same thing here.

It does usually lead to WAY more animation though. The Arcade Card was preposterously big. Idiotically huge, frankly.

[Arkhan]

Awesomely huge, actually!

[sunteam_paul]

It's like having a second stomach. It might take longer to fill it, but you can eat so much more tasty cake.

[Black Tiger]

Games don't have to fill the entire Arcade Card space. If it had been supported longer, we would have seen all kinds of variations of load times, especially for ports of moderate sized games. It's just the ones that take full advantage of the space that take long to load.

[Necromancer]

Games don't have to fill the entire Arcade Card space. If it had been supported longer, we would have seen all kinds of variations of load times, especially for ports of moderate sized games. It's just the ones that take full advantage of the space that take long to load.

Like the bi-compatible games where the extra ram is used to hold the extra bits instead of reloading every time you enter/exit different areas.

[SignOfZeta]

Games don't have to fill the entire Arcade Card space. If it had been supported longer, we would have seen all kinds of variations of load times, especially for ports of moderate sized games. It's just the ones that take full advantage of the space that take long to load.

Like the bi-compatible games where the extra ram is used to hold the extra bits instead of reloading every time you enter/exit different areas.

Which games are these?

[Necromancer]

Which games are these?

Brandish, Popful Mail, and likely every other SCD/ACD title that seemingly does nothing (unimproved cinemas).

[Keith Courage]

The ACD card adds the potential for a whole new library of bad ass games. Along with the disappointment that only like 8 were made. Half of which being games that were already on other consoles to begin with. 

I know the question was tech related.