The original Palm OS (4.1H) lacks SDIO support and reportedly has trouble formatting 128 megabyte SanDisk cards. The Treo 90 Updater addresses this problem and adds some other edits. The update is not a software patch but is burned into ROM.
The ROM 4.1H3 update allows the use of SD Cards up to 1GB (confirmed).
Additionally the new SDIO capability allows users to expand the device's features with two expansion cards: the Palm Bluetooth card, which allows the Treo 90 to access the Internet, email and messages wirelessly with a Bluetooth-enabled mobile phone and MARGI Systems Presenter-and-Go which connects the Treo 90 directly to digital LCD projectors or other VGA devices to show business presentations stored on the Treo in full color.
Read more about this topic: Treo 90