31 replies to this topic

[breaker]

I don't think Wonko is strange. He is enthusiastic, honest, friendly and conscientious.

Many people here have "thanked" him.

He is also gentle, polite, mannerly, decorous, courteous... far better than me.

He also lives in a civilized society. He does not speak rudely, far better than some people here...

Yes, true. I don't mean it in a bad way. It was done with a smile and affection.

[breaker]

Wrong, computers count from zero, the hard disk is no different. See here about "absolute sector 0" which is the "first sector" http://mirror.href.c.../mbr/STDMBR.htm

[Wonko the Sane]

Wrong, computers count from zero, the hard disk is no different. See here about "absolute sector 0" which is the "first sector" http://mirror.href.c.../mbr/STDMBR.htm

Not in the case of Sector numbers, please §@ç#ing make sure to READ what you quote:

1[/size] of your first Hard Drive by the so-called "undocumented" DOS command:
“ FDISK /MBR .”
Here's a disk editor view of how the MBR is stored on your hard disk's first sector; that's Absolute (or Physical) Sector 0 or CHS 0,0,1. (See Examination of the Code below to find out where this data ends up in the Memory of your computer.)

I was trying to disambiguate the problem of addressing sectors, just like the Starman tries to do above.

If you want to listen, good, if you don't want as well good.
If you want to agree, good, if you want to disagree, as well good.

Before telling me I am wrong, you may want to learn a bit more.

This is my FINAL statement:

• Sector 1 is first sector, as Sectors, unlike Heads and Cylinders are numbered starting from 1 in CHS notation.
• Sector 1 is first sector, as Sectors are NOT numbered in LBA notation. The LBA data that you see in a partition table is NOT LBA "Sector number", but rather (Absolute) OFFSET of the Sector, or, as said "Sectors Before" and for sector 1 it is obviously 0. LBA in itself means Large Logical Block Address and again obviously the Address of Sector 1 is 0.

Feel free to disagree, but don't tell me that the above is wrong, as it is PERFECTLY ACCURATE.



Wonko

[breaker]

Not in the case of Sector numbers, please §@ç#ing make sure to READ what you quote:



I was trying to disambiguate the problem of addressing sectors, just like the Starman tries to do above.

If you want to listen, good, if you don't want as well good.
If you want to agree, good, if you want to disagree, as well good.

Before telling me I am wrong, you may want to learn a bit more.

This is my FINAL statement:

• Sector 1 is first sector, as Sectors, unlike Heads and Cylinders are numbered starting from 1 in CHS notation.
• Sector 1 is first sector, as Sectors are NOT numbered in LBA notation. The LBA data that you see in a partition table is NOT LBA "Sector number", but rather (Absolute) OFFSET of the Sector, or, as said "Sectors Before" and for sector 1 it is obviously 0. LBA in itself means Large Block Address and again obviously the Address of Sector 1 is 0.

Feel free to disagree, but don't tell me that the above is wrong, as it is PERFECTLY ACCURATE.



Wonko

True, perhaps I am easily confused, or perhaps you weren't perfectly clear until now, I don't know. I usually speak about the absolute sectors, not the DOS stuff.... Anyway, thanks, I'm sure the clarification will help others. Now that you clarified you were using CHS notation, and not physical/absolute addressing, it makes more sense. The reason I was stuck on zero, is when I use a hex editor the output offset starts at zero, and on the Starman's page, above the hex dump, he labels the first sector as zero. Anyway, I have a computer that uses Normal instead of LBA from the BIOS, you were speaking about LBA, so how does Normal or Large affect the numbering?

Thanks and peace to you.

later dude,

breaker

[Wonko the Sane]

.... when I use a hex editor the output offset starts at zero, and on the Starman's page, above the hex dump, he labels the first sector as zero.

Exactly.

If you talk about sector number is one thing, if you talk about it's offset it's another.

If you use "sector number", this kind of thing DOES NOT exist in LBA notation.

I made a mistake however.

LBA actually means Large Logical Block Address, corrected previous post.

The two data fields in a Partition table, at offset:

• 454/470/486/502 dec (4 bytes) <-"StartSector" or "Start LBA" or "Sectors Before" or "Offset of the sector"
  and
• 458/474/490/506 dec (4 bytes) <-"Total Sectors" or "Num Sectors" or "Sectors in partition"

As often happens, and not unlike the confusion about disk and drive I pointed you earlier, lots of people (not only you) commonly say that:

Sector 1=LBA Sector 0

Which is a perfectly acceptable convention, as long as LBA or "Absolute" is specified, or however the fact that 0 based numbering is used.

The Starman in his pages alway refers to the same sector as first Sector or Sector 1 or CHS 0,0,1 or Absolute Sector 0, which is very accurate.

One should always make sure that what he says or writes is as accurate and not misunderstandable, sometimes it is difficult to disambiguate something, example:
http://mirror.href.c.../mbr/AA55H.html

The Wikipedia article on LBA:
http://en.wikipedia....lock_addressing
further clears this probably subtle difference between "sector number" and it's "LBA Address".



Wonko

[breaker]

OK, thanks for the further clarification. However, we should note LBA wasn't always part of the PC-BIOS, although these days obviously it would be rare to have a true CHS (<504Mbyte) drive. More info for the masses: http://www.dewassoc...._drives/lba.htm

It also seems more clear (to me) to say first sector = LBA sector 0 instead of sector 1...

Anyway, we can certainly agree, for the purpose of grub4dos, etc, that - http://en.wikipedia....ter_boot_record is a good overview of the PC-BIOS MBR scheme.

[Wonko the Sane]

[quote name='breaker' post='94831' date='Mar 16 2010, 07:11 AM']It also seems more clear (to me) to say first sector = LBA sector 0 instead of sector 1...[/quote]
Yep , that's fine.
Though of course it is not "natural" to start counting from 0.

Even most "simple" minds count "1, 2, many".

But of course in computing it can be a perfectly respectable and useful choice :
http://lua-users.org...CountingFromOne
http://www.cs.utexas...08xx/EWD831.PDF

[quote name='breaker' post='94831' date='Mar 16 2010, 07:11 AM']OK, thanks for the further clarification. However, we should note LBA wasn't always part of the PC-BIOS, although these days obviously it would be rare to have a true CHS (<504Mbyte) drive.[/quote]
Please do understand that you still miss some of the parts of the plot.

504 Mib (NOT Mb) has nothing to do with the "switch" between "pure" CHS addressing and LBA, from the very page you linked to :
[quote name='http://www.dewassoc.com/kbase/hard_drives/lba.htm']While it is true that a drive enabled for LBA is not subject to the 504 MiB drive size barrier, there still remains considerable confusion about Logical Block Address and what it does. Many knowledgeable technicians and users believe that it is LBA addressing that avoids the 504 MiB barrier, however this is not quite accurate.[/quote]


You have to put historical data in the right perspective :
http://www.dewassoc....ze_barriers.htm
or, better:
http://www.pcguide.c...d/bios/size.htm
(and ALL pages from there)
the size that actually determined the "need" for the switch was actually EITHER 1024x240x63x512=7,927,234,560 1024x255x63x512=8,422,686,720

Once you have perused tha above, do read these:
http://www.pcguide.c...d/bios/bios.htm
http://www.pcguide.c.../bios/modes.htm
http://www.pcguide.c...d/bios/over.htm
and particularly these:
http://www.pcguide.c...tensions-c.html
http://www.pcguide.c...s/modes_LBA.htm
http://www.pcguide.c...mparison-c.html



Wonko