[SOLVED] Why there is no 3GB pendrive?

Why there is no 3GB pendrive? We have the pendrives whose memory storage values are in powers of 2 (ex: 2GB, 4Gb, 8GB....). But there are no pendrives with 3GB, 6GB or 10GB. Why?

mgjosh said:

Why there is no 3GB pendrive? We have the pendrives whose memory storage values are in powers of 2 (ex: 2GB, 4Gb, 8GB....). But there are no pendrives with 3GB, 6GB or 10GB. Why?

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Its because of memory addressing.. say if you have three address lines.. then how many locations you can point to with those 3 lines.. its 2 raise to power 3 means 8.. so its same.. memories are made this way because memory is nothing but address locations where each address is storing a bit..

So, we get memories in storage memory related to 2 raise to powers and not the odd or middle values..

Is it clear to you now?

ya its clear about the pendrives. But we do get hard disks of middle values(40GB, 80GB, 160GB) which are not powers of 2. How is this possible?

Hard disks are magnetic memories not semiconductor. Pendrives have semiconductor memories inside. They are arranged in rows and columns. Semiconductor memories requires address lines to address a memory. While magnetic memories are divided in to sectors. They have different addressing mechanism. There is reading head that moves over magnetic surface. So to address a location you need to control head position.

yadavvlsi said:

Hard disks are magnetic memories not semiconductor. Pendrives have semiconductor memories inside. They are arranged in rows and columns. Semiconductor memories requires address lines to address a memory. While magnetic memories are divided in to sectors. They have different addressing mechanism. There is reading head that moves over magnetic surface. So to address a location you need to control head position.

Click to expand...

rightly said buddy!.. i hope mgjosh is not having any doubt now..

---------- Post added at 06:55 ---------- Previous post was at 06:53 ----------

A bit of further understanding:

Tracks, Cylinders, Heads, Sectors & Geometry

A Track is a ring of data or Sectors that moves under a specific Head as the disk rotates. A Cylinder is made up of the vertically in-line or stacked rings of data that are moving under all the drive Heads. So while Cylinders and Tracks are not exactly the same thing, the value or number for Cylinders is the same as the value or number for Tracks.

CHS ...Cylinder/Head/Sector addressing.
* Cylinder -- how far in or out the drive heads are positioned.
* Head -- which one of the heads is in use.
* Sector -- which segment of the disk is accessed, as it rotates underneath the selected drive head.

Modern hard drives are a complex "black box" which masquerades as a simplistic CHS drive. All EIDE or ATA drives accomplish this by performing an internal translation, which presents the complex internal storage of sectors as the simplistic CHS configuration which is claimed by the drive electronics.

Due to the universal nature of this internal translation, the drive can actually be configured using any combination of total Cylinders, total Heads and total Sectors, which does not exceed the capacity of the drive. While a specific configuration of Cylinders/Heads/Sectors used to access a drive is called a geometry. (a.k.a. drive geometry or CHS geometry).


Once a drive has been prepared for use (partitioned and formatted), then the same geometry or configuration of Cylinders, Heads and Sectors must always be used to continue accessing the drive. As any change to how the sectors on a hard drive are addressed could prevent all access to the data, or even result in destroying the existing information.

hi guys.. now its clear to me.. thanks to aggpankaj2 and yadavvlsi..