Shipments of PDAs remain on a downward spiral, according to newly published data from analyst firm IDC. 

Just 1.6 million handheld computers were shipped in the past quarter, down 16.9 per cent on the same period last year and representing an 8.8 per cent decline since the previous quarter in 2005.

Manufacturers are not ready to give up on the PDA market, however, and keep adding features such as GPS receivers.

The latest models could result in a short-term rise in shipments in the holiday season, but will not turn the tide, IDC projected.

While Palm and HP held on to the number one and two spots in overall shipments, they also showed the steepest declines. Palm saw shipments drop 22.7 per cent and HP suffered a slip of 35.5 per cent year-over-year.

The good news for Palm is that its Treo line of smartphones is doing extremely well, outselling PDAs in this quarter for the first time.

Acer more than quadrupled its sales and surpassed Dell to reach the number three spot.

IDC defines a PDA as a pocked-sized device that can be synchronised with a computer. It does not include models with telephone capabilities, such as the Palm Treo or BlackBerry.