While hard drive makers advocate a hybrid disk drive that places flash memory cache with the physical disk drive, Intel thinks the cache should be on the motherboard. Its Santa Rosa notebook platform will include 256MB of flash and can look like a ReadyBoost device or a hybrid disk accessible to ReadyDrive, said Kishore Rao, product line manager.

Panabaker said hybrid drives are a better design for ReadyDrive, since they keep the cache and disk under the management of the storage subsystem. "Microsoft has concerns about the issues associated with such a separated nonvolatile cache," Panabaker said.

"We don't see that as being an issue," said Kishore, adding that Intel's Matrix storage manager chip will safely handle all I/O operations. Disk drive makers say problems with flash on the motherboard will be harder to service, while Intel counters that the hard disk is more likely to fail, and when that happens the user must throw out the flash along with the disk.

"It's difficult to predict how this is going to play out with PC manufacturers," said Rydning at IDC. But users aren't likely to care, as long as computers that use the technologies perform and cost the same.

Jack Weilandt, chief technologist and director at Westwood, Mass.-based NSTAR Electric & Gas Corp., sees an 8 percent to 12 percent increase in battery life as "marginal at best," and added that faster boot times are mitigated by the fact that "more boot time is spent in authentication and managed desktop component loads than in the loading of Windows itself." But he said the durability of hybrid drives is attractive.