MiniSD card into RAM?

[GoldenTiger]

I think the reasons this isn't feasible or worth bothering with are already well-outlined in the thread, so I'll just add that in addition to all of that, SD cards usually only have a write cycle of about 1000 writes, so using them for this sort of application (if it were even worth it, which it's not) would result in spent cards very quickly.

[snake0721]

Originally Posted by gbm85

You guys are misunderstanding how the page file works on Windows. WINDOWS DOES NOT USE THE PAGE FILE / READYBOOST AS MORE RAM!! It takes unused memory (i.e. from programs that are not currently being used) and writes it out to disk. While this would certainly be possible on a PDA, it would be pointless. It would take longer to write out unused memory to a flash card than it would to just close the program (which Windows Mobile currently does) and then open it back up when you need it again.

That being said, couldn't you just move some of the usual phone RAM nibbling but not so important processes to the card? and we aren' talking writing MB and MBSs of files, so I hardly doubt the "take forever to write" thing would have much of an effect.

Matt Ayers, when asked if Readyboost technology (such as the one we are discussing) is just putting the paging file onto a flash disk. He answered, "Not really. the file is still backed on disk. This is a cache - if the data is not found in the ReadyBoost cache, we fall back to the HDD."

The point of what many in arguments for the feasibility of establishing this "readyboost mobile" technology, is that the RAM on the phone does in fact look into the Harddrive anyway, why would this card not be able to outperform the HDD?

The earlier quoted Ayers even said, "This isn't a separate page file store, but rather a cache to speed up access to frequently used data."

So yes, you are correct... to some degree.

I'm seriously not talking about the feasibility of making the card ACTUAL RAM here, I am just talking a pseudonized RAM of sorts that gives better performance. I would love to see my SD card slot increase my text message loading speeds, or even my contacts list access. nothing major, just smaller things to allow the real RAM to focus on the bigger issues.

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[dishe]

snake0721, I think you're still misunderstanding how readyboost helps a PC.
Spinning hard drives are slower than solid state memory, especially when it comes to quick short bursts of access (the drive has to wait until the relevant info is under the spindle, the effect of which is a measurement of time called latency).
Solid State memory, such as SD cards, are not as fast access as RAM would be, however they don't suffer from the latency of a spinning disk. That is why solid-state computers without a hard drive like the Asus EEE PC can boot windows XP in under 10 seconds even though its got outdated specs (900Mhz celeron CPU and only 512MB of RAM).

The downside to having a fully solid-state computer is that the size of the storage is severely limited (The average EEE PC only has 4-8GB of storage). So, the most efficient solution is a combination of spinning disk drive for size, and a solid state chip for caching what doesn't need to be in RAM.

The reason this doesn't apply to our Windows Mobile devices is that there is no spinning disk drive! Our memory is ENTIRELY solid state!
Whatever speed benefits you get from avoiding the latency of a spinning HD don't apply here. The only way you'll load stuff faster from storage is if its already in RAM (since RAM is faster than the EPROM storage chips and SD cards), and since we have very limited RAM to begin with, the whole conversation is pointless. It won't go any faster even if you managed to cache to SD.

Hope this helps clear things up.

[snake0721]

Well, I know what you are saying, and I fully knew the differences between spinning and SS harddrives.

But to simply write off what appears to be a case-and-point issue based solely off of the idea that "so and so is this way, therfore that isn't possible" seems a bit prematurely concieved.

I like to think that there are more possiblities with the hardware and software available to us through this phone. I'm honestly not here to convert, just to discuss; so ultimatums and absolutes are quite beyond my care in this case, I like to think of new possibilities.

Why not try, instead of just casting it off based off preconcieved notions of what's possible or pointless?

"The men who try to do something and fail are infinitely better than those who try nothing and succeed."
~Lloyd Jones

[pmoreau]

Does the processor used in the Mogul have full MMU support?
That is also needed in order for virtual memory to work, assuming they came up with some ultra-fast flash/ram device card that could be plugged in.

[omnicronx]

Many of you guys are confusing the max data transfer speeds with actually read and write times. Flash memory in theory is MUCH MUCH faster when reading than any Hard drive but its sustained transfer speeds are on par or lower. That said, I have never noticed a program take more than 10 megs of ram on my device (with most programs being under 4M), so sustained transfer speeds means little to nothing and the actual read and write times become much more important. SD cards can also be writing too many more than 1000 times, I don't know the actually number, but when you consider that current SSD hard drives are rated to run for 5 years with a high average or writes, I don't think it would be an issue on a mobile device, when there is only a fraction of the amount of writes. (after all, pre WM5 devices were all flashed based, and some of my friends still have their devices and it is going on 3-4 years.

In the end something gives me a feeling this limitation is not because of flash memory speeds, but because of the way windows CE memory management works. Too bad, because it looks like I am going to have to upgrade my apache.. just not enough ram..

[XGuard04]

This whole topic is quite simple actually. In short, you do not gain much by using flash memory to perform this function. Here is why...let's start with the example of a computer:

Memory is referenced in a hierarchy as stated before. All information is stored at the top level, which is your HDD. Then there are memory levels below that.

HDD
^
Virtual Memory (Part of HDD just on the inside of disk)
^
RAM
^
L2 Cache
^
L1 Cache

As I'm sure most of you already know.

Depending on the structure of the computer architecture the rules for paging memory can vary but this is a typical case. Frequent memory accesses are always kept as close to the lowest level as possible. If you are running an application it will be requested by RAM from the HDD, then by L2 from RAM, L1 from L2 then kept in L1 (there is more to this than I want to get into). This allows your programs to work quickly by making the most frequent cases the fastest case. You'll notice here that your HDD cannot function as your RAM because of speed constraints, this is the way the architecture is designed.

This is what people are proposing:
uSD--|
^ .....|
RAM <|
^
L2
^
L1

Likewise your internal Flash for program storage is at the same level as uSD, consider it a different drive.

How can you have uSD function as "RAM"? Page references are already being taken from uSD when an application on the card is referenced!

Additionally, "Expanding your RAM" won't give you much since the read/write speeds of the uSD are so much slower than RAM. (You might might as well be referencing from a higher level in the heiarchy, since higher levels are slower.)

For those of you that use ReadyBoost as an example, HDD's are exceptionally faster than flash memory when comapred to squentially referenced pages (which is what many memory references from a higher level end up being). (Wikipedia is biased and sometimes ill informed.) Readyboost comes into play in certain situations when random pages need to referenced that are not sequentially read from a higher level (say a program thats smaller than a page size). (This is because the initial latency for a HDD to spin up and begin reading data is longer than reading/writing data for a small burst.)

This is a difficult topic to explain in a thread however most people who have taken a computer architecture class would understand this. This is a topic usually left to academia or those directly involved with researching this topic. (I do not mean those two comments in a demeaning way, I am only trying to inform .)

Hopefully this helps some people and if you have a question or discrepancy with what I have said please reply, I might have wrote something wrong!

BTW:
GO GATORS! EEL4713! (I knew it would finally come in handy!)