HDD's - the Advertized size vs the Actual size.

They are not lying. To actually get 920gb you have to design and machine a drive in decimal to a higher rounded figure. You seem to forget the mechanical and tooling side of manufacturing. The standards and methods of measurement have to be by physical not binary methods.

They won't be using something like 1.2tb but a rounded off capacity there as well as what is seen as a manufacturing standard as well as the marketing side. IF you need a full 500gb+ you would go with the next drive size of 640gb or 750gb.

For a full 1tb you would then go to a 1.5tb model since once a drive is filled to the max it becomes inaccessible and typically sees the "out of memory" type errors. In other words you plan on buying a drive with a litle over the amount of space you need. You wouldn't be able to fit 750gb of data on a "true 750gb" drive there meaning the next size up would be needed even if only 920gb available.

fseal,

If you are interested, if you buy OSX Snow Leopard, it displays a 1TB drive as 1TB when formatted.

Obviously there is no right or wrong answer here. Consumers have felt they were mislead for years and all manufactures continue to label their drives the same way they always have.

The word kilo has been used as an SI standard for a very long time to mean 1,000. It does not actually mean, 1,024 as a computer would read it.

As a consumer, I'd much rather say that I purchased an 80GB hard drive rather than saying that I just purchased a 74.59236587 GB hard drive. It's just so much simpler.

I'd feel that this was marketing if hard drive manufacturers made a change from base 2 to base 10...but it's always been base 10. Then, they put a disclaimer on the box explaining how they arrived at the drive size. They didn't change midstream when they realized it would make them look better. And tell me why a hard drive mfg like Samsung doesn't take a firm stand and advertise their drives as 74GB and let the rest of the industry continue to just say 80GB? Don't you think "some" people would buy that 74GB drive out of principal...because they didn't feel mislead.

Trust me, I've seen the posts on the Apple forums where Snow Leopard fanboys say that "with their coveted machine", an 80GB hard drive gives you all 80GB. Rest assured that drive has exactly the same amount of space available as any other drive under any other OS and you will store exactly the same amount of data.

If you consider how you look at a file, if you see a file that is 1,000,000 bytes...would you not say that it's 1 megabyte in size. Or would you instead say that it's 95.3674316% of 1 megabyte since 1 megabyte to the computer is actually 1,048,576 bytes.

Another way to look at this, lets say that you have a movie file on your computer that is exactly 200GB in size. Windows would display this file as 214,748,364,800 bytes. I think most people would eye ball that file and say it's 214GB in size....and they would likely be shocked and amazed when that 214GB file fit on their 200GB Seagate hard drive. But trust me, it will fit, as 214,748,364,800 bytes is exactly the same size as a hard drive advertised as 200,000,000,000 bytes in size. It's exactly the same thing. You haven't lost 1 single solitary byte.

VelociRaptors have a 74gb model. That's not an even 80gb but 68.91787052154541gb in actuality. As far as a video 214,748,364,800 bytes in size most would more likely see that rounded off to 414.75gb +or- a few bytes.

The marketing decision is mainly geared towards novice not advanced users looking at how to calculate actual sizes as well as the standards used in manufacturing.

Manufacturers advertize the rounded off figure not the actual amount of bytes seen using the decimal unit of measurement. A 500gb drive in bytes when looking at a post screen for example would show 500,000,xxx,xxx with the Xs representing numbers other then 0s being seen showing the actual figure is over 500 billion.

Note that uses the rounded to 1000 not 1024 figure with the physical form of measurement in decimal while the OS uses the binary form. People forget there are two totally different methods being used for calculating drive capacities. The decimal form is based machine tool standards not OS standards simply being rounded off to the 500gb figure.

Brilliant,thanks for this nice insight.
I noticed the differences,but now i have some answers.
Good job.Thanks
BTW,even with similar hdd's,let's say each 1 TB,there are differences..I wonder..

Some years back when running a WD 250gb drive I was seeing some 234gb available while some running Seagate were typically seeing 232gb. You will note small variances between companies as well as various model drives at times but minor.