All Memory, All The Time, Revisited

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Almost eighteen months ago, I wrote an article about running at least the core functions of a machine exclusively in RAM.

In an era when we can’t count on CPUs getting more powerful, what has been happening since then?

One positive development since that article was written has been the emergence of XPLite. One can now strip XP down to less than half its normal size, which makes running Windows and a reasonable set of core apps with a 2Gb RAMdisk reasonably possible.

Another is that memory prices have dropped to the point where 2 or 4Gb will gouge your wallet rather than take your leg off along with it.

Some might say that USB flash drives could fit the bill, but they’re much slower than even hard drives at transferring data, so they aren’t a solution.

For those who just want to stick 4Gb of RAM into memory slots and use that, as we mentioned in the earlier article, keep in mind that RAM is dynamic. That means everything in it goes away when you turn the power off, and you’re not going to save much time if your boot gets extended thirty seconds to fill up a RAMDrive.


Unfortunately, not all too much has changed for the company that makes the product we mentioned in our earlier article, a reality rather pointed noted in the company’s forums.

The solid state drives the company sells still are very expensive, they still aren’t bootable, and perhaps most importantly, just aren’t very fast because they’re bottlenecked into the old PCI bus.

It’s pretty hard to justify a $1,700 for a 2Gb RAMdrive when the throughput is only twice that of a fairly mundane RAID setup.

If you take a look at another company that makes similiar devices, the picture is much the same

Clearing Up The Bottleneck

PCI is heading out the door. PCI Express is coming. An x1 PCI Express slot is supposed to give you 250Mb/sec throughput. That’s almost double the current rate for the whole PCI bus, but that’s still quite a bottleneck.

Another possible route is SATA 2.0. If you had a device that could work with it, you could get up to 300Mb/sec from it. Again, better, but still not terribly good.

Are there any other possibilities?

Well, PCI Express isn’t just limited a x1. A PCI Express video slot is an x16, which means it can transfer at 4000Mb/sec.

Ah, this is more like it!

Problem is, your average motherboard is going to have just one video slot, and running a supersystem with a PCI video card would not sit too well with most potential customers.

However, in the near future, it looks likely that there will be at least motherboards with two PCI Express x16 slots. These are meant for two video cards, and it may prove to be extremely difficult or impossible to get that particular slot to do RAMdisk rather than video.

But it’s something worth somebody to look into, isn’t it?

In fact, someone apparently has looked into the technology enough to make some sort of arrangement with Cenatek to make a bootable RAMdrive that seems to offer even more than 4Gb/sec performance. However, this company is rather controversial, as this link illustrates.

Even if you take the company’s word on the product, if you look at the fine print of the technical specs, you’ll find the company say that “Stand-alone performance limited to 400MB/sec Burst/ 320MB/sec Sustained R/W and 50.000 IO/sec.” The company claim they’ll have an extended cache system for the RAMDrive which will yield the multiGB/sec rates, but the drive doesn’t natively do this.

Conclusion

What we need is a RAMDisk that is:

  • bootable
  • not a whole lot more expensive than the cost of the RAM
  • able to take advantage of a very fast I/O slot somehow and somewhere.

    PCI Express x16 would be ideal, but a PCI Express x4 slot would probably do well enough. Firewire might prove to be good enough, too.

    Eventually, I think this will become mainstream once RAM gets cheap enough. Obviously, this isn’t going to happen any time soon at mainstream prices.

    But a future mainstream technology has to start somewhere, and there’s enough nuts enthusiasts (it’s OK to say that, I’m one of the nuts :)) out there who’d be willing to lay out a grand or maybe even two to get the kind of device I’m talking about to get the wheel rolling.

    Ed

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