Weekly Classic Computer Trivia Question (20141205)

Johnny Billquist bqt at update.uu.se
Sat Dec 6 12:48:16 CST 2014

On 2014-12-06 15:02, Peter Corlett wrote:
> On Fri, Dec 05, 2014 at 11:35:54PM -0500, Mouse wrote:
> [...]
>> "The standard"?  That disagrees with my experience.  I have numerous disks
>> from the days when capacities were several tens of megabytes, or low hundreds
>> of megabytes; they are all labeled accurately.
> My ratty old tiny disks are all in storage so I can't pull a few out and check
> the CHS/LBA versus the marked capacity, but I note that When it comes to mere
> megabytes, 1000**2 and 1024**2 are still close enough for it to be lost in
> rounding errors.

For megabytes, the difference isn't that big, true. When you get to 
gigabytes it starts becoming significant, and when we talk terabytes, if 
definitely more than a rounding error.
For one terabyte, the difference is close to 10 gigabytes...
(For one meg, the difference is 48K).

>> Somewhere around the time of single-digit gigabyte capacities, disk
>> manufacturers started mislabeling their disks.  That they were doing so
>> knowing it was an actively misleading practice is evidenced by the notes in
>> ads from that era (and even on some drives), saying things like "based on 1GB
>> = 1 billion bytes", which, if the metric meanings were indeed the standard
>> you seem to be claiming they were, would not have been worth mentioning.
> Actually, the notes in the ads were added later due to litigious bastards and
> other chancers claiming that they believed it to mean powers-of-two and making
> a nuisance of themselves in court.

Once upon a time, disks actually were also given their size in powers of 
two, so no, I'm pretty sure you are wrong about the order of things. 
That would would have thought the size were in powers of two were 
natural. At some point, some clever marketing people realized that if 
they changes to actually use the power of ten prefixes instead, they 
could inflate their numbers, and fool those poor suckers who still 
thought the numbers were powers of two. Thus upping one on their 
competitors as well. Of course, it didn't take long for the competitors 
to just copy that idea, and there we are today...

> This power-of-two confusion is an artifact of how solid-state memory devices
> are made, and does not apply to everything vaguely related to computers.
> Otherwise one could try and argue that a "dozen eggs" should contain 13 eggs
> because bakers add an extra loaf to a batch as an artifact of the bread-making
> process.

Uh... Not sure where the eggs enter into my computer, though...
The power-of-two issue is not because of how solid state disks work, but 
how computers work. In general, you *always* means things in powers of 
two in computers. The exception nowadays being disks. But main memory, 
cache, speeds, are all measured in powers of two.

Actually, I should say, everything related to data. Anything that 
originates with a bit.

Frequencies are not power of twos, for instance.

> Consider also the infamous 1.44MB disk.  That number comes from 1440 * 1024, so
> apparently a megabyte is *also* 1,024,000 bytes.  If we can humpty-dumpty it
> and pluck numbers out of the air, why not just call a megabyte 3,141,592 bytes?

Actually, the 1.44MB floppy holds 1,474,560 bytes.
512 bytes per sector, 18 sectors per track, 80 tracks per side, and two 
sides... Where did you pull the 1440*1024 from???


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

More information about the cctalk mailing list