By Zach Spear

Published: 10:25 AM EST

Apple's next-generation iMacs are being held up for business reasons and a minor technical obstacle, according to one Wall Street analyst.

"We wanted to give an update on the Mac business from what we are picking up from our latest supply chain checks," Kaufman Bros. analyst Shaw Wu wrote in a report to clients Monday. "While new the iMac appears to be almost ready for primetime, what is holding it up appears to be business reasons and a potential small technical hurdle."

Specifically, Wu said his sources indicate that external casing changes will likely be modest and that "Apple is in the midst of figuring out whether to power the new iMac with Intel quad-core processors or more high-powered dual-core processors with larger caches."

Back in November, Taiwanese rumor site DigiTimes claimed Apple was waiting for new quad-core chips from Intel so it could "launch products based on" the new processors, but did not specify in which systems Apple would use the parts.  Intel subsequently rolled out the new processors just last week.

Wu said he was surprised Macworld didn't bring new iMacs and believes Apple may be hesitating on quad-core processors for the iMac on fears that the decision could cut into Mac Pro sales.

"While quad-core would provide a material improvement in performance and potentially jumpstart sales, it could cannibalize the Mac Pro, its high-end tower, whose low-end configuration is currently a quad-core," he wrote. "Apple could choose to stick with dual-core on the iMac or make 8-core the new low-end for Mac Pro."

Wu's concern may be misplaced given acting chief executive Tim Cook's comments during Apple's fiscal first quarter earnings call last week. Asked about Apple's Pro segment, Cook admitted that Mac Pro sales are sluggish given the "current economic climate", and that Apple's desktop business is "primarily iMac."

In addition, Wu said he's also picked up on chatter that the iMac's vents and cooling systems may see a redesign to deal with higher heat dissipation.

A report from last December noted that the cooling module for the next-gen iMacs would be manufactured jointly by Foxconn and Auras Technology. Given that the report, which provided no further details, singled out the cooling system, it led to speculation that the new iMacs may employ a different cooling system than current models. Whether that's actually the case remains unclear.

In his report to clients Monday, Wu suggested that one final variable delaying the release of new iMacs could be the timing of Snow Leopard.

"While Leopard would take advantage of multiple cores, Snow Leopard takes it to the next level with better support for multi-core, multi-processors, and OpenCL, with enhanced graphics capability," Wu wrote.

The Kaufman Brothers analyst now predicts an iMac refresh in the March quarter or, given additional delays, the June quarter at the latest. Those claims conflict with earlier predictions from the Chinese-language Economic Daily News, which cited supply chain sources as saying new iMacs were due to arrive in January.