Kinda OT: Why I'm not waiting for Santa Rosa

From Daily Tech ( http://dailytech.com/article.aspx?newsid=4605 )

Santa Rosa will have either 512MB or 1GB of NAND flash built into the chipset (the amount will depend on the manufacturer of the motherboard) -but the same level of caching can be accomplished with either a hybrid hard drive or any flash memory that's accessible by Vista. Since just about all laptops are coming with card readers I know what I'm going to do with the 2GB high speed SD card that's sitting unused in my old Pocket PC...

 

That's on topic.. just say "asus" and you're ok.

You bring up a very good point and an even better solution... It's a good idea.

 

Yes, but how fast are those flash readers? The only I have on my desktop is hung off my USB2.0, so it's limited to 480Mb/s max, well less then SATA 2.0 at 3Gb/s. I haven't tried the SD reader on my Z33 - my digital camera uses CF cards - but even if it is off the PCI bus it is limited to 1Gb/s, still slower then SATA.

In order to maximize performance, the flash cache should be at least as fast if not faster then the drive it is caching. The best way to do this is to either put it on the drive, or on the chipset somewhere.

I think Intel is betting that with perpendicular recording allowing for increases in HD density and speed, the drive manufacturers will be slow to integrate NAND into their drives, so they are taking the chipset approach to make sure everyone can benefit from the speed increase/power savings regardless of what the drive companies do.

 

When will hybrid hard drives go mainstream... cheaply? Also, doesn't flash memory have a read/write lifespan? Isn't something like this exactly the type of use that would kill a flash device as fast as possible - i.e. for the same reasons putting an OS on a USB stick is not recommended? To quote Wikipedia:

~ Brett

 

Are we talking about the same "flash" memory cards here? Last I checked flash memory has some serious limitations that prevent it from becoming the technology that the article seems to claim it to be---the most serious of which is the finite number of writes you can perform to the memory before the chemical process used in the flashing stops working. The standard number of writes is around 1 million for a decent flash card, and this is a blink of an eye if you integrate it onto a chipset for cache purposes. You could do stuff in software to extend this a bit, but then that defeats the whole purpose of using it in a cache role.

Also, flash memory is frickin' expensive! Ever wonder why 4GB of flash will cost the same as a standard 80GB HDD?

Edit: dammit Nrbelex you steal my thunder

 

They probably address the write cycles limited life problem in three ways:

1. better technology.
2. error detection & correction (e.g., for a hybrid HDD read the data directly off the disk if it's corrupted)
3. in specific instances such as storing boot data on the flash, the memory is more often read than written.

I don't think these three completely solve the problem, unless a really radical change in technology happens whereby 1. solves it completely. But, we'll live and see...

 

Aaaah thanks, I was wondering why flash drives weren't replacing Hdds

 

But the speed of the SATA buss is irrelevant -you'll never get data to or from a hard drive at the buss's maximum speed. 480Mb/s is screamin' fast when you're talking about hard drive data...

 

Yup -but the write erase life cycle of NAND flash will still exceed the life span of a hard drive. The heads will crash, or you'll upgrade the drive, before the NAND flash stops working...

 

From: http://www.mil-embedded.com/articles/authors/spanjer/

 

480Mb/s is not as fast as it looks. I think it's 12MBs/s.

 

Indeed. However, presumably the flash memory integrated on the mainboard or used as HDD cache will have much better read/write rates.

Of course, this doesn't help if you want to use an external cache (i.e. SD card, USB pendrive). By what I've read so far (and it's not much) I expect that would not be a very efficient solution.

Another edit: actually, 480Mbps is 60 MBps. Simply because one byte is 8 bits. That's already quite respectable. Maybe not as much as the integrated flash would have, but still, respectable.

 

480Mbs / 8 bits in a byte = 60 MBs. But that's a max theoretical transfer rate -time for the CPU to move the data around + USB packaging will drop that figure down. However that's still faster than you'll ever move data to or get it from a hard drive...

 

Wow what a great idea, I have a high speed 4 Gb sd card...interesting...
Guess I could even plug in my 4 GB flashdrive..although I wouldnt want that sticking out all the time.

 

Most USB readers top out somewhere in the 20-30MB/s range, I think, and the USB key drives a bit slower.

I just bought one of the new Seagate 7200.10 drives for my desktop, and it has an average sustained read speed in the 50MB/s range, with burst to 235MB/s for the 16MB RAM cache. I believe that properly mounted flash memory on a high bandwidth bus like SATA or a motherboard interface would be almost as fast as the RAM.

 

You are forgetting about access time, which is the primary degrading factor.
Simply put flash maybe is slower than HDD in burst mode, but in random access it's faster.

 

Is the point of this figuring out whether you can use vista in premium mode with a merom chipset and a flash drive?

If so Im looking for the answer still spelled out.

 

I believe the point was that a large part of the touted advantages of Santa Rosa can be gained by using current or upcoming technologies like hybrid hard drives or flash drives with no major read/write limits to speak of. I don't think that using a standard flash drive or sd media card or anything like that would be a good idea though since they're not made to withstand the constant read/writing Vista would put them through.

~ Brett

 

This article was timely.


If it's still undergoing the Slashdot effect, try this link.

~ Brett

 

I'm not perfectly clear on the way flash memory is going to be implemented, but I don't believe that hybrid HDDs and Robson Technology are fully interchangable. The way I see it is that the flash memory in hybrid HDDs is more of an extension of the RAM in hard drives and so will cache frequently used files for quicker access. Flash isn't as fast as the RAM cache, but it'll save on platter access time.

Robson Technology looks to be a more static solution where say the major of the OS files, startup programs, and drivers are placed on the motherboard flash. These are not frequently modified which avoids the limited write issue and it'll allow quicker start-up since all the files are together and don't require searching. Hybrid hard drives may end up having a lot of system files in their flash memory, but that would be based on frequent access while Robson could also carry drivers or programs that are infrequently used or only used at startup.

Robson Technology flash memory would also be faster in the end since it'll have it's own dedicated interface and be closer to the chipset while flash on hybrid HDDs have to go to the RAM cache and through various controllers and converting between protocols which adds overhead.

 

I'm trying to dig up some more info on HDDs. If the NAND flash is mapped as the first part of the root partition then I don't see how it would differ from that same memory being built into the chipset -although the chipset NAND might have more bandwidth...

 

Thanks Brett -excellent post!

 

Has anybody tried the ReadyBoost feature of the Vista Betas with a USB stick? It sounds like a quick way to destroy one...

And question number 2: Is Santa Rosa required for the effective use of a hybrid hard drive? i.e. - Will the Asus refreshes being shipped today be able to take advantage of the "ReadyDrive" feature of Vista or will we have to wait for the next refresh?

~ Brett

 

I'd be curious to see what the performance is like with a SD card in a laptop's built in card reader.

As for your second question: I don't think that HDDs are chipset dependent -it seems to me that the only requirement for any kind of NAND flash boost is Vista...