Investigating Intel's Turbo Memory: Does it really work?

Problem 2: Why did things get slower?

In our initial look at Santa Rosa and Intel's Turbo Memory we generally found that performance wasn't improved and in some cases it got significantly worse. Take for example the amount of time the notebook took to go into hibernate mode:

With Turbo Memory enabled, the system took another 11 seconds to hibernate. Going back to our explanation of what Turbo Memory is supposed to do, it isn't supposed to reduce hibernate time at all. At best, the ReadyBoost portion of Turbo Memory can make data available a little quicker after waking up from hibernation but that's it. Needless to say, the technology isn't designed to make hibernation times any slower. Clearly we needed to do some digging.

In our first article we showed no performance difference between Turbo Memory enabled vs. disabled in the PCMark '05 HDD test. Given that we disabled Turbo Memory using the console it appears that it remained enabled in both tests, making the scores useless. Armed with our new found information on how to properly test with Turbo Memory, we took another look at PCMark '05.

The PCMark '05 HDD test is composed of real world disk usage, played back in a manner similar to what we do in our hard drive reviews. The individual tests are as follows:

Windows XP Startup: This is the Windows® XP start trace, which contains disk activities occurring at operating system start-up. The test is 90% reading and 10% writes. This trace contains no user activity.

Application Loading: This is a trace containing disk activities from loading various applications. It includes opening and closing of the following applications:

- Microsoft® Word

- Adobe® Acrobat® Reader 5

- Windows® Media Player

- 3DMark®2001SE

- Leadtek® Winfast® DVD

- Mozilla Internet Browser

The application loading trace is 83% reads and 17% writes.

General Hard Disk Drive Usage: This trace contains disk activities from using several common applications. These are:

- Opening a Microsoft® Word document, performing grammar check, saving and closing

- Compression and decompression using Winzip

- Encrypting and decrypting a file using PowerCrypt

- Scanning files for viruses using F-Secure® AntivirusTM.

- Playing an MP3 file with Winamp

- Playing a WAV file with Winamp

- Playing a DivX video using DivX codec and Windows® Media Player

- Playing a WMV video file using Windows® Media Player

- Viewing pictures using Windows® Picture Viewer

- Browsing the internet using Microsoft® Internet Explorer

- Loading, playing and exiting a game using UbisoftTM Tom Clancy's Ghost Recon

The General Usage trace is 60% reads and 40% writes.

Virus Scanning: Virus scanning is a critical task in today's PC usage. As the major bottleneck of scanning viruses is in hard disk activity, it is reasonable to include virus scanning as a HDD test. The test consists of HDD activity of scanning 600MB of files for viruses. The Virus Scanning test is mostly disk reading (99.5%).

File Write: This trace contains disk activities from writing 680MB files on the hard disk and no read operations are involved in this test.

Disk idle times have been compressed to 50 milliseconds to speed up the playback time. Our studies showed that 50 milliseconds was the smallest idle time interval that didn't affect the test results. The results of the HDD tests are reported in Megabytes processed per second.

Basically PCMark takes the disk accesses from these various usage patterns and plays them back as fast as possible. The tests are grounded in the real world but the actual performance metrics that result are skewed to favor very fast disk subsystems. In the case of Turbo Memory, we're testing its prefetching algorithms for getting data into the cache.

The results are particularly impressive, performance in the XP Startup, Application Launch and General Usage tests is at worst double with Turbo Memory enabled. Clearly the same isn't true in the real world as we weren't able to measure any improvements in system boot or application start times, but the technology is working at least in this controlled environment.

The numbers that are most intriguing are the file write numbers, because this is the only test were performance goes down when Turbo Memory is enabled. The write speed to the flash memory isn't nearly as good as to our 7K100 test drive, which echoes what we saw with the hibernate entry test, which is fairly write intensive.

According to Intel, the system hibernating shouldn't be slowed down by Turbo Memory but Intel engineers have duplicated the test results we're seeing. It seems like the write speed of the flash memory is to blame here, causing performance degradation when there's a lot of writing (e.g. hibernating). Whether or not this behavior can be seen on all Santa Rosa laptops has yet to be determined, but it is a definite issue we've encountered with Turbo Memory.