See if this helps you..

 You cannot go beyond 1000 waypoints, but you can fill the card with POI's

 Here is a forum topic on groundspeak about just this such thing.

http://forums.groundspeak.com/GC/index.php?act=ST&f=11&t=140808

On 9/10/07, Richard Daines <rjdaines@gmail.com> wrote:
>
> Regarding a 2 Gig card, my 60CSx read the card but I certainly could not
> load up the whole thing with maps.  Not sure if it's my problem or the units
> limitation.  I'm not really interested in loading POIs and tracks on it.  It
> would be really nice to break the 1000 waypoints limitation with the card
> but I think they are all stored on internal memory.
>
> On 9/10/07, ShadowAce <shadowace.az@gmail.com> wrote:
> >
> >
> >   Question:  What is the largest size microSD card that I can use in my
> > X-series GPS unit?
> >  *Answer:*
> >
> > At this time, the *2* *GB* cards are the largest microSD cards that can
> > be used for the X-series GPS units. However, the X-series GPS units are not
> > compatible with the San Disk Ultra II cards and therefore we do not
> > recommend using the Ultra II micro *SD* cards with any of the X units.
> >  Last modified on:  06/01/2007 From Garmin
>
>