I have four gig ram in both the X200 and the X301 -- but I've seen posts here and there about the turbo memory -- sounds like not something I may need, but I would like to understand what it is -- is it just a more "high-powered" ram and does it replace a regular ram stick? guess maybe I should just google, but I was hoping I might get an answer simple enough that I could understand -- I don't understand much more than hard drive and ram, but I would like to learn a bit as I go along -- thanks very much, ThinkRob, for your response
It's more akin to a fast SSD, used for caching frequently-used binaries/libraries. If you've got plenty of RAM and a sane OS, however, the OS will be a lot more reluctant to page out said frequently-used code -- so there's a reduced benefit of having such a cache. Further, if you've got a fast disk, then "Turbo Memory" won't really help much, since paging in something from disk won't incur as much of a performance penalty. In fact, if you've got a fast SSD (such as an X25M/X25E), seek times and random access performance will be good enough that there's likely to be no benefit whatsoever from having that sort of cache available.
Now I haven't done any benchmarks myself -- but from what I've observed, the scenarios in which it is helpful are as follows:
1) You have limited RAM. "Pinning" frequently used programs to "Turbo Memory" will indeed allow them to be read from a fast, low-latency device in the (likely) event that they are evicted from main memory due to memory pressure.
2) You have a slow disk. "Pinning" an application allows it to be read from something faster than your disk.
3) You've got a normal disk under a heavy seek load. Again, reading from the cache will be faster than disk, plus it has the added benefit of not increasing the disk's outstanding request queue.
Scenarios in which it is of questionable benefit:
1) You have plenty of RAM and rarely use all of it. Any sane, modern OS will try to keep libraries, etc. around in RAM whenever possible. If you've got plenty of memory, chances are that you won't be doing a lot of completely-"cold" launches -- so having a fast cache from which to read application data is probably of little use.
2) You have a fast SSD. Yes, the bandwidth of Mini PCI-E is greater than that of SATA II -- but I'd be amazed if Turbo Memory was significantly faster than, say, an X25M or an X25E. If you've got an SSD with good random I/O performance, having a second SSD for caching (which is essentially what Turbo Memory is) won't produce much of an improvement. It might produce some, but you're probably better off putting the money towards a faster SSD, since that will have far more benefits.
3) You have limited RAM or a slow drive, and haven't purchased Turbo Memory yet. In this case, take all the money you were going to spend on Turbo Memory, and purchase more RAM or a faster drive. You'll gain a lot more for it, and you'll end up with an extra free Mini PCI-E slot.
Need help with Linux or FreeBSD? Catch me on IRC: I'm ThinkRob on FreeNode and EFnet.
Current laptop: Lenovo ThinkPad T420 (running Debian Wheezy) - kestrel [pending retirement]
Current workstation: IBM Intellistation 9228 (running FreeBSD 9.1) - blackbird