Whats the relationship between MegaBytes and Megabits?

Tab

Lifer
Sep 15, 2002
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This might have been posted before, but I still don't understand it. According to my friend their is no relationship between Megabit and Megabytes. Is this true? Also, is it true that the only reason we use Megabits to refer to bandwidth is because we never change our standards. In the 90's and earlier going 1MB/s was insane. My question is how big is one Megabit (In KiloBytes) and how big is one Gigabit (In Megabytes). If it isn't possible to convert them perfectly or correctly how long would it take to transfer a DVD over a Gigabit line and over a Megabit Line?
 

Lonyo

Lifer
Aug 10, 2002
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There are 8 bits in one byte, so the relationship is 8 megabits = 1 megabyte.
A one megabit connection would be 1024 kilobits.
1024/8 (bits in a byte) gives 128 kilobytes.

One gigabit is 1024 megabits which is 128 megabytes.

RAM chips are measures in megabits as well - a RAM chip with 512megabit means that on a stick or RAM with 8 chips you get 512/8*8 = 512megabytes.

Hope that helps.
 

Tab

Lifer
Sep 15, 2002
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Sort of I think... I'll look at it later when I am not at school :p
 

dullard

Elite Member
May 21, 2001
25,644
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Originally posted by: Tabb
Wait, now let me look at this 1,000 Kb is really 1Megabyte it just that marketing world that screwed it up?
Now you opened a can of worms, almost every thread that mentions this turns into a long flame fest. The Anandtech FAQ describes the answer well. But to summarize:

1) The true math definition of megabyte is and always has been 1000 kilobytes (which in turn a kilobyte is and always has been 1000 bytes).
2) Programmers and computer hardware designers got lazy and instead used 1 megabyte = 1024 kilobytes (and 1 kilobyte = 1024 bytes).
3) However things were inconsistant even within group #2. For example hard drives always used 1000 and not 1024. Even Windows got screwed up. Asking Windows the size of a file (or folder, or drive) with one method in Windows used 1000 while other methods used 1024.
4) Recently everyone got together in an attempt to fix the inconsistancies. Their results: 1 megabyte = 1000 kilobytes = 1000*1000 bytes (the true mathematical definition). New terms were created. 1 Mibibyte = 1024 kibibytes = 1024*1024 bytes. If only we would actually use the new gibi, mibi, kibi, etc words no one will ever be confused again.

Anandtech FAQ
 

Pariah

Elite Member
Apr 16, 2000
7,357
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Originally posted by: Lonyo
There are 8 bits in one byte, so the relationship is 8 megabits = 1 megabyte.
A one megabit connection would be 1024 kilobits.
1024/8 (bits in a byte) gives 128 kilobytes.

One gigabit is 1024 megabits which is 128 megabytes.

RAM chips are measures in megabits as well - a RAM chip with 512megabit means that on a stick or RAM with 8 chips you get 512/8*8 = 512megabytes.

Hope that helps.

Data transmission rates are decimal not binary, so a one megabit connection is 1000Kb/s (12.5MB/s) and a gigabit connection is 1000Mb/s (125MB/s). Storage is measured in binary (usually) so your RAM calculations are correct.
 

Tab

Lifer
Sep 15, 2002
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Data transmission rates are decimal not binary, so a one megabit connection is 1000Kb/s (12.5MB/s) and a gigabit connection is 1000Mb/s (125MB/s). Storage is measured in binary (usually) so your RAM calculations are correct.
one megabit connection equals 1,000,000 bits
divide that by 8 to get to bytes, correct? and one would get 125,000 bytes. this is not 12.5 Megabytes as you said. it is 125 kB, or .125 MB. also along the same lines, a giga bit connection equals 1,000,000,000, which divided by 8 to get to bytes gives 125,000,000 bytes, 125 MB, as you said.

is a DVD measured in the true Gigabytes or in gibibytes? what are compact discs, flash memory, nvRam, and other stuff measured in? the true base 10 measurements or base 2?
 

daballard

Member
Feb 9, 2004
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First off, the whole reason bits is specified is for marketing reasons. People like seeing big numbers.

Also, it's quite standard for lower case b to stand for bit and upper case B to stand for byte.

Your dvd, stored in gigabytes is in the ture sense of the term, 1024 MB, because this is the amount of memory it takes up.

I hope this helps.
 

Pariah

Elite Member
Apr 16, 2000
7,357
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Sorry, I went brain dead there. I was thinking of fast ethernet (100mbps) when I said 12.5 MB/s.

DVD's are decimal, CD's are binary, and all electronic storage (RAM, flash, etc) that I know of is binary.
 

Tab

Lifer
Sep 15, 2002
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So, why did programmers and hardware manufactures get lazy all the sudden?
 

jcwagers

Golden Member
Dec 25, 2000
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Um....your question has probably already been answered but here's my shot at explaining it using my cable connection.

2 megabit connection / 8 bits per byte = 2000/8 = about 250 kilobytes a second at full speed.

Wow.....I probably didn't help at all. :(

jc
 

Tab

Lifer
Sep 15, 2002
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User 1 : they measure two entirely different things
User 1 : its like trying to relate inches to cups
User 2: No, its not.
User 1 : in computers they are related in a lot of ways
User 1 : but they are different measurements entirely
User 2: megabits can be converted into megabytes
User 2: or vice versa
User 1 : when dealing with bandwidth they have a direct relation meaing you can predict speed from your bandwidth
User 2: WTF?
User 2: You said, they had NO relationship.
User 1 : they are related in some cases
User 1 : they are two different things
User 1 : but they can have relations
User 2: So, what you said was incorrect.
User 1 : i never said they didnt have any relation
User 1 : they are two different things
User 2: Thats bull, you told me thay had no realtionship.
User 1 : in cases of like hard drives and CPU and bitrate of sounds
User 1 : most of the time they are totally different things
User 1 : no comparison
User 2: Don't start with HDs...please I just got used to using mibi and gigi
User 1 : and the reason a megabyte is 1024 kilobytes
User 2: No, thats wrong.
User 1 : is becuase the smallest HD sector is 512 bytes
User 2: A mibi is really 1024. Devlopers screwed up.
User 1 : because of the bit rate
User 2: Your going against the metric system.
User 1 : it never was metric
User 1 : we just borrowed the prefixes
User 2: ......
User 2: The real defintion of mega byte is 1000 kilobytes, the true defintion of a
User 2: and so on
User 1 : but in actuality
User 1 : its 1024
User 2: Why?
User 1 : cuz the smallest HD sector is 512 bytes
User 1 : cuz of the 16 bit coding
User 1 : or 8 bit i think ACSII is...
User 1 : hmmm
User 2: Yea
User 1 : i dont remember
User 2: This is going on AnAndtech
User 1 : a bit is a 0 or 1
User 1 : on or off
User 2: ye
User 2: s
User 2: a bit is 8 bytes
User 1 : 8 bits make up one ASCII character
User 1 : which is 1 byte
User 1 : so there is some relations in size
User 1 : but a bit is still an on or off
User 2: Yea..?
User 1 : and a byte is still the smallest measure of filesize
User 2: Yes, whats your point?
User 1 : one is measure of size
User 1 : and the other is just a switch
User 2: or a measure of switches...

Okay, tell me who is right. Or what we are not understanding.

User 2: How long would that take.
User 1: estimatation
User 1: lol
User 1: estamation
User 2: I want it exact, and I want the math.
User 1: okay
User 1: be back in about 1 minute
User 2: Leaving when it gets confusesing....
User 1: the average transfer would be around 128 mb/sec
User 1: assuming that all the way through
User 2: How did you convert that mathmatically?
User 1: 34.16
User 1: seconds
User 2: What?
User 2: Show your work, not someone else's
User 1: i like my calculator
User 2: Yea, I need TI-86.
User 1: 1 gigabit
User 1: is 1024 megabits
User 2: Okay....
User 1: divide by 8 assuming of course this is transfered with ASCII stuff and all blah blah
User 1: 128 megabytes/sec
User 1: its an estimate
User 1: there's too many factors to be exact
User 1: and a 4.27 gigabit?
User 1: gigabyte
User 1: thought it said bit before
User 1: nm
User 2: A dvd is 4.27 Gigabytes
User 1: 4.27 x 1024 = 4372.48
User 1: megaBYTES
User 1: so divide that by 128
User 2: you got 128 froM?
User 1: gives you 34.16 seconds

 

bob4432

Lifer
Sep 6, 2003
11,718
44
91
the gigabit lan is not going to be your bottleneck unless you are using server equipment, ie 64bit slots and new fast scsi hdds. the problem will be your hdd and 32bit pci slots, considering it is a normal pc with a ide/sata hdd which will give you a approximate sustained data transfer of about 50MB/s for a big file like that.

even on a 100Mb(12.5MB)/s lan the fastest i have seen things transfer is about 10MB/s according to DU Meter with my normal computers.
 

Pariah

Elite Member
Apr 16, 2000
7,357
20
81
I don't follow that conversation at all. In the first part where you keep talking about "they." I can't even figure out what "they" are supposed to be. And in the second part again, I don't understand what you are trying to calculate, you didn't post the beginning of the exchange. How long would what take? None of that makes any sense.

DVD's are not 4.27 GB using any counting system. They're listed at 4.7GB (4.7 billion bytes) by marketing, but that's decimal. However Windows calculates storage capacity in binary, so the useable capacity is 4.37GiB (binary) in Windows. To convert decimal to binary, you have to divide the decimal value by 1.024 for every full digit grouping. 4.7GB (4,700,000,000 bytes) has 3 full digit groupings, so you divide 4.7 by 1.024 3 times and end up with 4.37 binary GB's.

Hard drives are not binary or decimal, they simply contain X number of 512 byte sectors for their total capacity. What determines whether their capacity is given in binary or decimal, is solely based on who is calculating the capacity. All MS based operating systems and basically all other mainstream OS's calculate disk capacity in binary, while hard disk makers advertise capacity in decimal. They're both describing the same number of bytes, they're just using a different method of measurement, sort of like using the metric and Imperial systems to measure the same distance. Even though the distance is the same, there will be fewer inches than centimeters. The only problem here is that binary and decimal use the same names to describe their different methods of measure.

Data transmissions (network, HD interface, memory speeds) are decimal because they are a measure per unit time which isn't binary. For example, current SCSI wide standards consist of a 2 byte transfer (16 bits) per clock doubled cycle (2 transfers per cycle). SCSI 320 runs at 80MHz (80 million cycles per second), so you multiply 80 million by 4 bytes (2 two byte transfers) and end up with the theoretical 320 milllion bytes/sec transfer rate (320MB/s). Notice because the clock rate is decimal (MHz = 1,000,000/sec, NOT 1,048,576/sec), that the final answer is a decimal value where MB - 1 million bytes, not 1,048,576 bytes.