Vista ReadyBoost

Don Bradbury tries out Vista's novel way of adding cache memory via flash devices.

While most computers running Vista will come with at least 1GB of RAM and their owners will find the machine runs smoothly enough in undemanding situations, Microsoft has added ReadyBoost to the spec of their latest OS. It's aim is to improve performance by using suitable (mainly fast) non-volatile flash memory - such as a USB flash drive or a fast memory card - to act as cache memory where the computer can access data more quickly that it could access it from the mechanical hard drive.

ReadyBoost makes use of the intelligent memory management of Windows' SuperFetch technology (see footnote). When you first install your flash device, Vista checks it to see if its performance is good enough to use as ReadyBoost memory.

You are asked if you want to use the device's capacity, or part of it, to speed up performance, and how much you want to leave as simple storage capacity. A slider bar lets you change the default recommendation.

Windows makes comments on this, and it won't let you specify an unacceptable split. The actual tests the OS carries out include the amount of available space on the device, its write and random read performance, and checks that these are consistent over the entire range of the memory you're adding - a failing of some flash devices.

Requirements

You must add at least 235MB of total capacity, but you can nominate that less than this should be made available to ReadyBoost. Basic standards include a speed of 2.5MB/sec for 4KB random reads, and 1.75MB/sec for 512KB random writes. The data transfer performance in practise will depend on several factors, including the capability of the PC and the design of the flash chips within the device you're adding. A certified ReadyBoost Ready device will have been checked out by the manufacturer, but some Vista users may be surprised to see that flash memory they've had for some time will still past the Vista test for ReadyBoost compatibility.

Such was the case here, where older USB flash drives were rejected, but a fast 1GB Integral Secure Digital card was declared suitable. We carried out tests using this, loaded via a built-in memory card reader on a Vista notebook (note that add-on card readers may not be suitable). For notebook users, memory cards have the advantage of not only not consuming one of the precious USB ports but also it doesn't stick out from the machine, just waiting to be knocked, bent, or broken like a USB stick would.

Vista does provides basic benchmark software, but it appears that this is not suitable for checking to see if the machine's performance is measurably increased with ReadyBoost cache memory installed. In any event, it showed minimal difference on our test computer.

So, on this notebook test machine, which used shared memory for graphics out of a total of 1GB of installed RAM, the increase in indicated performance was not huge, and that seems to be the general conclusion from users for machines running with 512MB or more of memory. The overall smoothness of operations may be improved, however, and if you push the machine to its limits there may well be advantages to be had from the addition of ReadyBoost cache memory. Much will depend on the uses you put to the computer.

How much to add?

In terms of capacity, it's recommend that you use a 1:1 ratio of flash to system memory at the low end of memory installed and, at larger amounts, as high as 2.5:1 flash to system memory. Adding more than that isn't helpful. ReadyBoost uses the flash drive to create a copy of virtual memory and while this is not quite as fast as your main RAM memory, it's substantially faster than looking to the hard disk for it.

Bear in mind the declared principle that there's nothing stored on the flash disk that isn't also on the hard disk. It's claimed that if you remove the flash drive, Vista's memory manager will detect the change and automatically look to your hard disk. However, we have found applications that didn't want us to dismount the flash memory cache while that application was running. Play it by ear, as they say.

A final factor to be borne in mind in this regard is any available power options the computer provides. These can significantly affect performance, and you would have to determine whether the cache memory was beneficial in any of these power modes.

In conclusion

Worth a try, then. ReadyBoost is there if your machine can benefit from it. It's not as effective as adding more RAM to your computer, particularly if the machine is short of main memory, but do try your existing stock of flash devices by all means, though you may find you need to buy a ReadyBoost certified upgrade. And do consider alternatives to USB devices; a fast and suitably capacious SD card, for example, borrowed from your digital camera perhaps, or other flash memory device may be suitable to try.

Since there is a threshold for adequate performance with these devices, some will necessarily be born "more equa" than others, as Orwell would have said, though it will probably be marginal. Your selection may not prove to be the very best, therefore, but give it a try and see what you think.

Footnote on Microsoft's SuperFetch

A new memory management technology in Windows Vista, Windows SuperFetch, helps keep the computer consistently responsive to your programs by making better use of the computer's RAM. It prioritizes the programs you're currently using over background tasks and adapts to the way you work by tracking the programs you use most often and preloading these into memory. With SuperFetch, background tasks still run when the computer is idle. However, when the background task is finished, SuperFetch repopulates system memory with the data you were working with before the background task ran.

 

Don Bradbury