It's no accident that the first hybrid hard drives are 2.5-inch laptop drives. Samsung said last month that it had begun shipping samples of its first H-HHD, and Seagate Technology is expected to follow suit any day. The Samsung drives in the 2.5-inch series will combine 80, 120, or 160 Gbytes of rotating storage with 256 Mbytes of flash memory. Seagate's first drives will be in the same configuration, 2.5-inch drives with 256 Mbytes of flash, and the company has said it will produce drives with larger flash buffers of 512 Mbytes and 1 Gbyte in the second half of this year.

That 256 Mbytes of flash will be shared among several cache functions, says Ruston Panabaker of Microsoft's Windows Hardware Innovation Group, who gave a presentation on ReadyDrive at last year's Windows Hardware Engineering Conference. Here's how Panabaker broke it down:

>> About 10 Mbytes of it will be devoted to caching the hard drive's firmware.

>> The next 32 Mbytes will be used as a write cache. Laptop drives spin down to save power, and a write cache in flash means that writes can be accumulated and the disk left off longer.

>> Another 32 Mbytes will be available for caching data and program code that supports hardware features and Vista's new Windows HotStart function. HotStart ties a program function to a hardware button so that users can do things like run a media player, browse and play files from the hard disk, or open an e-mail program with one click, whether the laptop is on, sleeping, in hibernation, or off.

>> Whatever flash memory is left is set up as a ReadyBoost that SuperFetch will use to cache code pages while it works to maintain optimal memory content, and to accelerate the boot and resume processes.

This not only improves the laptop's performance, according to Panabaker, but it can save 4% to 12% of the machine's battery power by allowing the hard drive to power down while the flash cache stays on to serve cached code to the CPU and aggregate writes to the disk.

FAVORITE BOOTS

ReadyBoot is a little too much like ReadyBoost to be clearly differentiated, but that may be the point. After every boot-up, the ReadyBoost service does an analysis of the files read during the last five boots, then builds a list of the files it predicts will be used in the next boot, in what order and their locations on disk. When the PC boots up, the ReadyBoost service creates a compressed cache of those files. That serves the right files in the optimal order to boot the machine faster.

If the computer is equipped with an H-HHD, ReadyDrive can accelerate the boot process even more. When a shutdown or hibernation is initiated, ReadyDrive loads data required early in the boot process to the H-HHD's flash cache. When the disk is powered on again, even though it won't spin up for 2 to 4 seconds, data can start flowing from the flash memory almost immediately.

As we said at the start, there's no substitute for system memory, so if you want to run Vista, load up on as much as your machine will hold (or you can afford, whichever comes first). But if you've got a machine with a limited amount of system RAM, such as on an older PC or a laptop, flash memory and the ReadyBoost technology that's in every copy of Vista can make a difference. An "Enhanced for ReadyBoost" flash drive or card can give you an immediate shot in the arm, and, when they get here, hybrid hard drives will help as well.

Look for flash technology vendors to start exploiting the direct relationship between flash memory and Vista performance gains. As Vista is adopted by more and more PC users, the result will undoubtedly mean more flash in our future. And everybody can use a little more flash.