Hacker News Reader

Hacker News

Comment by mikece | Hacker News Reader

Full thread

mikece

Because the International System of Units isn't binary? That's why we use GiB in computing.

https://en.wikipedia.org/wiki/International_System_of_Units

View on HN

"we" should use GiB, but in practice (almost) no one really does. Hence the confusion...

I always assumed it was a sales gimmick: more GB fit in storage device than GiB.

That it did. I can assure you that in the 80's when I was first learning about computers no one thought that a kilobyte was 1,000 vs 1,024... that said right now, without looking it up I cannot tell you how much a megabyte is so perhaps it was a bad idea to begin with.

Edit: Looks like it's 1,048,576

> without looking it up I cannot tell you how much a megabyte is

You just need to remember that you need to multiple by 1,024 instead of 1,000.

So 1 kilobyte is 1,024 bytes, 1 megabyte is 1,024 kilobytes so 1,024x1,024 = 1,048,576 bytes, 1 gigabyte is 1,024 megabytes, etc.

Yes, but if you can't recall the number by heart it's not really that useful as a number.

Depends. You know how floppy discs were advertised to be 1.44 MB? That was calculated as 1000*1024 bytes

It was double the previous 720 KB ones, so 1,440 KB, which they wrongly advertised as 1.44 MB, indeed. But that's irrelevant to my previous comment.

It used to be that we used k, M, G, etc as power of 2s in computing without any confusion because that was the norm.

But, somehow, at some point I believe that hard drive manufacturers started to use "GB" as meaning 10^9 bytes and the confusion started from there.

Why should "kilo-" in programming be different from "kilo-" in physics? It used to be a wrong approach and now people started to unwrangle the mess. SI was invented for a reason.

In the 1980s and 1990s, no-one thought this was a problem. All computer stuff is based on binary numbers, therefore 2^(10*n) makes a lot more sense than 10^n for us.

Do you buy 64 GB of RAM for a new computer? Or is it 68.719476736 GB?

It was only the hard drive manufacturers that wanted to inflate their numbers, and started pushing the 10^n scheme.

This is coming from someone who grew up with the SI system, which makes a ton of sense for physics and mechanics. Not so much for computer memory.

This is a myth. The very first harddrive was 5,000,000 characters - in the 1950s. The first PC harddrives came in 10 & 20MB. Harddrives have always been base10. Linespeed has always been base10. Clock speed has always been base10. It's RAM that's the odd one out.

I believe that where the disconnect has occurred, is that when home computing started - RAM is pretty much all you had. We didn't have megabit networking, we didn't have harddrives, if we were lucky we had cassettes. So the binary prefixes were absorbed in isolation.

No, 10MB or 100MB, etc. was measured using powers of 2. It's not true that it was always based 10.

It made a big stir when they reached GB range and changed to powers of 10. I remember it.

To quote Jerry, show me the money?

For example, https://www.ebay.com/itm/225315397038

The label of this drive gives us CHS figures for three different models:

           cyl * h  * s  *  B
  127MB =  919 * 16 * 17 * 512 = 127,983,616B (124MiB)
  170MB = 1011 * 15 * 22 * 512 = 170,818,560B (162MiB)
  340MB = 1011 * 15 * 44 * 512 = 341,637,120B (325MiB)

So we're at 127MB and they're already base10.

For some reason everyone remembers it, but no-one's been able to show me.

The base unit is actually a single bit, so why aren't we talking about decabits instead of bytes, following the SI argument?

Because deca isn't a good SI prefix, and only gets grandfathered in. Also because some people like weird derived units like moles. Fwiw, in many places ISPs advertise speeds in megabits per seconds, no doubt to sounds right times faster than they are.

> advertise speeds in megabits per seconds

"bits per second" is what it always has been for computer communication.

When I got started, I got a 300 bits/second modem, which later got upgraded to 1200/75 bits/s and then 2400 bits/second.

Later on, we had 57,6 kbit/second modems, 64 kbit/s ISDN lines, 2 Mbit/s ADSL, etc.

All the speedtest websites I've seen also use Mbit/s.

But sure, if I'm downloading the latest Ubuntu distro, I want to know the current speed in Megabytes/s.

Networks are often measured in bits.

It's more about tradition. And sometimes a sprinkle of marketing lies (it's cheaper to make 1024 GB SSD than 1 TiB SSD).

Disk /dev/nvme0n1: 953.87 GiB, 1024209543168 bytes, 2000409264 sectors

But neither bits or bytes are SI units or even derived units. They just adopted prefixes from there...

Reply on news.ycombinator.com