Although the weeks before January's Macworld Expo/San Francisco traditionally represent the calm before the storm for official product announcements from Mac vendors, the imminent arrival of Apple Computer Inc.'s biggest trade show of the year can be counted on to inspire a frenzy of activity among the Mac community's competing rumour sites. Despite Apple's renewed legal efforts to quash these sites in 2000 -- an effort that seems to have reduced the volume of postings to the sites in recent months -- the Mac rumour mill has come back swinging in time for Macworld Expo/San Francisco 2001. The hot product topic du jour: a new breed of subnotebook Macs. Ever since Apple discontinued its Duo line of dockable PowerBooks in 1997and cancelled the lightweight PowerBook 2400 a year later, there have been constant grassroots efforts lobbying Apple to resurrect a thin-and-light PowerBook along the lines of Sony's popular Vaio 505 series of subnotebooks. Many Apple watchers are predicting that Apple will use Expo to refresh its professional portable line with the much-discussed (and as-yet-unannounced) Mercury G4 PowerBook. In addition, rumour sites such as Mac OS Rumours and AppleInsider recently floated the possibility that the Mac maker will unveil a "CubeBook" -- this portable friend to Apple's stylish Power Mac G4 Cube that would fill the empty sixth category created in the Mac maker's product matrix when chief executive Steve Jobs introduced the Cube at July's Macworld Expo/New York. The empty spot on the portable end of Apple's matrix -- which the company stamped with a taunting question mark -- has whipped the Mac rumor mill into a feeding frenzy. The sites agree that the product will be a subnotebook designed to give the Sony Vaio 505 a run for its money. Translation: it will weigh in at three to four pounds and will measure about one inch thick when closed. Beyond size and weight, however, the sites differ dramatically on specifications and announcement dates. Mac OS Rumors claims the CubeBook will include a wide-aspect-ratio screen, CD-RW or CD-RW-capable DVD-RAM, a thin new battery and a new UMA-2 motherboard. The site's most surprising assertion: Production is scheduled to begin within weeks, and "we should see this remarkable ultraportable next month at Macworld San Francisco". AppleInsider reaches different conclusions. The site reported that the rumored "Vaio-like" subnotebook will be "nearly as wide" as the current professional PowerBook but "slightly more than half as long front-to-back". According to AppleInsider, the subnotebook will not ship "for at least eight months", presumably meaning Macworld Expo/New York in July 2001. So who -- if anyone -- is right? While sceptics suggest that Apple would be unlikely to risk consumer confusion by rolling out both Mercury and an Apple subnotebook at January's Expo, Apple optimists have reserved their predictions until after Jobs presents his last "Oh, and one more thing..." during his keynote presentation. Daniel Drew Turner contributed to this report. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.