Autor: Radoslaw Mielczarek (rmielczarek_at_lucent.com)
Data: Fri 31 Dec 1999 - 10:12:28 MET
Hej:
Spokojnie mozna zainstalowac wiekszy dysk niz bios widzi, podzielic go
sobie na partycje
i sformafowac odpowiednio pod nt4 z service pack 4.
Przed zainstalowaniem NT dobrze jest stworzyc partycje np.2G na system i
sformatowac ja pod dos.
Nie wszystkie systemy uzywaja biosa do komunikacji z HDD.
Mam 20G , Bios widzi 8G, dostepne 20G dla sys. operacyjnego.
Dla jasnosci z dokumentacji Linuxa:
4.1. BIOS Disk Access and the 1024 cylinder limit
Linux does not use the BIOS, but some other systems do. The BIOS,
which predates LBA times, offers with INT13 disk I/O routines that
have (c,h,s) as input. (More precisely: AH selects the function to
perform, CH is the low 8 bits of the cylinder number, CL has in bits
7-6 the high two bits of the cylinder number and in bits 5-0 the
sector number, DH is the head number, and DL is the drive number (80h
or 81h). This explains part of the layout of the partition table.)
Thus, we have CHS encoded in three bytes, with 10 bits for the
cylinder number, 8 bits for the head number, and 6 bits for the track
sector number (numbered 1-63). It follows that cylinder numbers can
range from 0 to 1023 and that no more than 1024 cylinders are BIOS
addressable.
DOS and Windows software did not change when IDE disks with LBA
support were introduced, so DOS and Windows continued needing a disk
geometry, even when this was no longer needed for the actual disk I/O,
but only for talking to the BIOS. This again means that Linux needs
the geometry in those places where communication with the BIOS or with
other operating systems is required, even on a modern disk.
This state of affairs lasted for four years or so, and then disks
appeared on the market that could not be addressed with the INT13
functions (because the 10+8+6=24 bits for (c,h,s) can address not more
than 8.5 GB) and a new BIOS interface was designed: the so-called
Extended INT13 functions, where DS:SI points at a 16-byte Disk Address
Packet that contains an 8-byte starting absolute block number.
Very slowly the Microsoft world is moving towards using these Extended
INT13 functions. Probably a few years from now no modern system on
modern hardware will need the concept of `disk geometry' anymore.
4.2. History of BIOS and IDE limits
ATA Specification (for IDE disks) - the 137 GB limit
At most 65536 cylinders (numbered 0-65535), 16 heads (numbered
0-15), 255 sectors/track (numbered 1-255), for a maximum total
capacity of 267386880 sectors (of 512 bytes each), that is,
136902082560 bytes (137 GB). This is not yet a problem (in
1999), but will be a few years from now.
BIOS Int 13 - the 8.5 GB limit
At most 1024 cylinders (numbered 0-1023), 256 heads (numbered
0-255), 63 sectors/track (numbered 1-63) for a maximum total
capacity of 8455716864 bytes (8.5 GB). This is a serious
limitation today. It means that DOS cannot use present day
large disks.
The 528 MB limit
If the same values for c,h,s are used for the BIOS Int 13 call
and for the IDE disk I/O, then both limitations combine, and one
can use at most 1024 cylinders, 16 heads, 63 sectors/track, for
a maximum total capacity of 528482304 bytes (528MB), the
infamous 504 MiB limit for DOS with an old BIOS. This started
being a problem around 1993, and people resorted to all kinds of
trickery, both in hardware (LBA), in firmware (translating
BIOS), and in software (disk managers). The concept of
`translation' was invented (1994): a BIOS could use one geometry
while talking to the drive, and another, fake, geometry while
talking to DOS, and translate between the two.
The 2.1 GB limit (April 1996)
Some older BIOSes only allocate 12 bits for the field in CMOS
RAM that gives the number of cylinders. Consequently, this
number can be at most 4095, and only 4095*16*63*512=2113413120
bytes are accessible. The effect of having a larger disk would
be a hang at boot time. This made disks with geometry
4092/16/63 rather popular. And still today many large disk
drives come with a jumper to make them appear 4092/16/63. See
also over2gb.htm.
The 3.2 GB limit
There was a bug in the Phoenix 4.03 and 4.04 BIOS firmware that
would cause the system to lock up in the CMOS setup for drives
with a capacity over 3277 MB. See over3gb.htm.
The 4.2 GB limit (Feb 1997)
Simple BIOS translation (ECHS=Extended CHS, sometimes called
`Large disk support' or just `Large') works by repeatedly
doubling the number of heads and halving the number of cylinders
shown to DOS, until the number of cylinders is at most 1024.
Now DOS and Windows 95 cannot handle 256 heads, and in the
common case that the disk reports 16 heads, this means that this
simple mechanism only works up to 8192*16*63*512=4227858432
bytes (with a fake geometry with 1024 cylinders, 128 heads, 63
sectors/track). Note that ECHS does not change the number of
sectors per track, so if that is not 63, the limit will be
lower. See over4gb.htm.
The 7.9 GB limit
Slightly smarter BIOSes avoid the previous problem by first
adjusting the number of heads to 15 (`revised ECHS'), so that a
fake geometry with 240 heads can be obtained, good for
1024*240*63*512=7927234560 bytes.
The 8.4 GB limit
Finally, if the BIOS does all it can to make this translation a
success, and uses 255 heads and 63 sectors/track (`assisted LBA'
or just `LBA') it may reach 1024*255*63*512=8422686720 bytes,
slightly less than the earlier 8.5 GB limit because the
geometries with 256 heads must be avoided. (This translation
will use for the number of heads the first value H in the
sequence 16, 32, 64, 128, 255 for which the total disk capacity
fits in 1024*H*63*512, and then computes the number of cylinders
C as total capacity divided by (H*63*512).)
For another discussion of this topic, see Breaking the Barriers, and,
with more details, IDE Hard Drive Capacity Barriers.
Hard drives over 8.4 GB are supposed to report their geometry as
16383/16/63. This in effect means that the `geometry' is obsolete,
and the total disk size can no longer be computed from the geometry.
siwy wrote:
>
> Posiadam plyte glowna SOYO 5BT-5.
> Moja wersja biosu to BT-2A3. SOYO 5BT 430 TX chipset.
> Setup nie widzi dysków powyżej 8 GB.
> Zamierzam sobie kupić dysk 13Gb IBM 7200.
> Czy jest szansa, ze to pojdzie?
> Z gory diekuje za wszelka pomoc !!!!
-- Radek
To archiwum zostało wygenerowane przez hypermail 2.1.7 : Tue 18 May 2004 - 19:28:52 MET DST