I've heard that the standardized spec for SD only goes to 2gig, but there were some companies that went under the TransFlash designation that pushed non-SDHC cards to 4gig, though I've never actually seen one. I've also heard they were dog slow if you DID manage to find one.
SDHC or Secure Digital High Capacity is the new standard for SD cards that can be larger than 2gigs (32gigs is the theoretical max for SDHC, I believe), but it's not compatible with anything that doesn't explicitly say it supports SDHC. SDHC cards use a different method for reading and writing than non-SDHC cards, though anything that supports SDHC is backwards compatible with non-SDHC cards.
At least, that's my understanding.
The R4 is not SDHC compliant, so you're limited to a 2gig max. I don't think it ever will be capable of larger (unless you manage to find one of those elusive non-SDHC 4gig cards, which, I suspect, have been discontinued as non-compliant to SD standards), but who knows what those wizards that are the R4 team might be able to pull off in a future firmware update. Though I feel it's unlikely that the R4 will ever support SDHC without some kind of hardware upgrade because the R4's firmwares are software based and don't physically change anything in the R4 itself.
Did that make any freakin' sense at all?
