Flash Vs Harddrive?

[Matt]

This may sound n00bish, but hardware isn't one of my specialties.. heh

I know that many music players anf usb drives are using what is called a Flash Drive. What is the difference between that and a HDD?

Matt

[murtu52]

Well, lets take a look at iPod-One of the largest audio player distributors.

iPods, as well as the photo, mini, and all the other provider's products, use the harddrive based storage method. The pros for this type of storage are that it can hold much more, as of current technology, than the flash based. Large capacity as in 4GB being one of the smallest needle-based harddrives out there.

iPods Shuffle (I just got one at a school raffle today, my b'day...so happy ), as well as the Creative Muvo, etc., use the flash drive storage method. There are many good things about this, one being that it requires a relatively small power amount to run, compared to the harddrives. Also, since it is composed of all non-moving parts, it is much more durable than the HDs. Although, our technology hasn't advanced far enough for the flash-drive based storage to take over the HD method; we are, i believe, in the 2GB-3GB area, while our harddrives are in the 500GB area.

The reason people use flash-drive based storage is because of one very important factor-the beating factor. If you drop a needle based HD, chances are the needle will be knocked away, thus rendering the HD completely useless. Flashdrives, as i said before, are comprised of non-moving parts, so dropping it won't mess it up too much. That is why many people who work out take flashdrives out with them.

Answers your questions? Any more questions u have?

[iccaros]

besides this quote , that I do not understand as there is no needl ein a harddrive (a record player yes harddrive no)

smallest needle-based harddrives out there

here is the diffrence..

a hard drive is a magnetic medium like a tape drive, but unlike a tape drive a hard drive is not liner. It can seek across a disk not just from beginning to end like tape.

A hard drive has a large write cycle before the magnetic medium on the disk surface will not longer be magnetically chargeable. This property gives you almost unlimited write and read cycles. The size of storage is only limited by the physical size of the magnetic head and the accuracy of the arm. As these drives are nothing more that a motor, a arm location controller, buffer memory and a magnetic disk (like a floppy but on metal instead of plastic). They are cheep to process.

http://computer.howstuffworks.com/hard-disk.htm

Flash Memory

Flash memory (sometimes called "flash RAM") is a type of constantly-powered nonvolatile memory that can be erased and reprogrammed in units of memory called blocks. It is a variation of electrically erasable programmable read-only memory (EEPROM) which, unlike flash memory, is erased and rewritten at the byte level, which is slower than flash memory updating. Flash memory is often used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written to in block (rather than byte) sizes, making it easy to update. On the other hand, flash memory is not useful as random access memory (RAM) because RAM needs to be addressable at the byte (not the block) level.

Flash memory gets its name because the microchip is organized so that a section of memory cells are erased in a single action or "flash." The erasure is caused by Fowler-Nordheim tunneling in which electrons pierce through a thin dielectric material to remove an electronic charge from a floating gate associated with each memory cell. Intel offers a form of flash memory that holds two bits (rather than one) in each memory cell, thus doubling the capacity of memory without a corresponding increase in price.

The key thing to know.. Flash is faster then disk. But flash has a limited number of writes. So things like swap files/partitions will destroy Flash memory in a matter of days.

http://computer.howstuffworks.com/flash-memory.htm

I have some CF to IDE addaptors adn I boot FreeBSD as my firewall. also I use as a harddrive for my satellite simulator at work as its linux build is only 4 megs in size... .

IBM (and now others) have 4 gig harddrives the size as CF disk. since the CF disk interface is compatable with IDE its easy to exchange the two .

[murtu52]

sorry, i should have addressed the question more specifically; the needle does not physically touch the disk. It simply reads/writes with magnetic forces.

What iccarros is giving you is the actual technology behind it, which are things i still have yet to even think about mastering...

[Matt]

Ok, I understand the HDD concept, but I'm not fully grasping Flash dirves. Say I had a music player using a flash drive, it has no moving parts, the memory is just read straigh from it in blocks, I guess. But you compared it to RAM. RAM erases after the device is turned off, so why is information (or songs) still available after you turn it off?

[murtu52]

i understand your question, though this is the best i can find from iccarros's link, from howstuffworks.com:

The difference is that Flash RAM has to have some power to maintain its contents, while Flash memory will maintain its data without any external source of power.

My understanding is that flash memory is only similar to RAM; even though they operate on similar principles, they have different methods of retaining data.

[iccaros]

sorry, i should have addressed the question more specifically; the needle does not physically touch the disk. It simply reads/writes with magnetic forces.

What iccarros is giving you is the actual technology behind it, which are things i still have yet to even think about mastering...

your answer was correct.. I just expanded on it..

[iccaros]

Ok, I understand the HDD concept, but I'm not fully grasping Flash dirves.  Say I had a music player using a flash drive, it has no moving parts, the memory is just read straigh from it in blocks, I guess.  But you compared it to RAM.  RAM erases after the device is turned off, so why is information (or songs) still available after you turn it off?

ragular arm is like a bucked that has a plug. you charge it.. and as long as you keep the charge on it, it stays that way.. so a charge is a logical one and no charge is a logical zero. once the charge goes away all the memory blocks become zero.

with flash we change the chip at the logical level with each write.. this is why it is also not as fast as normal ram and also why it has a limited amount of write cycles.

if you look up FPGA you will see a better understanding..

A field-programmable gate array (FPGA) is an integrated circuit (IC) that can be programmed in the field after manufacture. FPGAs are similar in principle to, but have vastly wider potential application than, programmable read-only memory (PROM) chips. FPGAs are used by engineers in the design of specialized ICs that can later be produced hard-wired in large quantities for distribution to computer manufacturers and end users. Ultimately, FPGAs might allow computer users to tailor microprocessors to meet their own individual needs.

so when we apply a charge we change the physical chip. in the case of memory for a logical one it now connects between two points.. if the connection is broken its a zero (like a switch). some kinds of silicon are made to act like a conducter when an amount of voltage is applied by can also be changed to a non-conductor with a reverse of the voltage. the programing voltage is always higher then the operating voltage. in the case of a PIC microchip the programing voltage is 24 DC while the operating voltage is between 3.5 and 5 VDC.

so in the end ..

ram has a state due to a charge applied..

Flash has its (switches) altered with each write.. so it needs no power to retain ..

in reallity.. after soem time flash will go back to its natural state.. but that is in the time of years so it really does not matter.

a good site to see

http://www.microchip.com/stellent/idcplg?I..._PAGE&nodeId=64

you can even program these with C (I use a thing called PicBasic pro... like C mixed with basic). they are fun to play with.. I have created two robots and some IR transmitters for serial communicaton (1900 baud). and a weather station that uses the IR tansmiter to talk to my computer..

Edited April 26, 2005 by iccaros

[Matt]

Thanks for the replies, I think I have a pretty good understanding now.

Matt