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| Re: Quicksilver "big drive" mystery solved [message #23643 is a reply to message #23621] |
Thu, 08 November 2012 12:05   |
peterhaas
Messages: 80
Registered: September 2012
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> A tip of the hat to the Mac OS 9 Lives website for getting to the bottom
> of a mystery.
A number of G4 motherboards, other than those mentioned, are internally
capable of LBA48 operation, and "persistently", too.
The "LBA48 Property" (which see, just Google it) may be persistently added
just about every QS 2001 and earlier G4 which I have personally had
experience with.
Whenever it (the drive's capability for >120 MB drives, which limit is
actually more like 131,072 MB, that is) has been detected it is necessary
to ship TWO packets of information to the drive to access the area greater
than can be defined by one packet.
The lower 128 MB is specified in the first packet; the remainder is
specified in the second packet.
The large drives are expecting TWO packets, but their firmware is designed
with a "legacy" mode which will only require ONE packet, hence why these
large and very large drives (up to 750 GB) work well as virtual 128 GB
drives.
Now, there are THREE versions of the LBA48 Property, depending upon
whether the the ATA bus controller is ATA-6, ATA-5 or ATA-4.
On most Macs, the hard drive bus is the faster of the two.
So, for a QS 2001 without the special motherboard revision, you would
apply the ATA-6 patch AND the ATA-5 patch, and that would give you full
large drive support on both buses. At least until the PRAM has been reset,
in which instance you must go back and add the LBA48 Property again.
But, the two buses (or only one, if you so desire) are indeed persistent
as the properties have actually been added to the PRAM of the motherboard.
For best compatibility, in case the LBA48 Property has been lost, it is
best to size your primary boot partition as 131,072 MB, or less. This
makes the boot partition accessible with a single packet, as described
above, and everything thereafter becomes accessible using dual packets, so
you can still recover from an inadvertent Cmd-Opt-P-R.
I have run some of my QS 2001 machines for years using this technique, or
Intech's "large drive" support extension.
The sheer beauty of the LBA48 property is it is already in the ROM, so you
may indeed boot from a very large partition.
With Intech's Hi-Cap extension, the capability of accessing very large
partitions is available only after OS X has been successfully booted,
therefor it is not usable for the boot partition itself.
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| Re: Quicksilver "big drive" mystery solved [message #23651 is a reply to message #23643] |
Thu, 08 November 2012 12:58 |
Mac User #330250
Messages: 83
Registered: August 2012
Karma: 0
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---------- Original message ----------
Subject: Re: Quicksilver "big drive" mystery solved
Date: Thursday, 08. November 2012
From: peterhaas@cruzio.com
To: g3-5-list@googlegroups.com
> The "LBA48 Property"
This Open Firmware NVRAM property does not work with Mac OS 9.
Although large drives (i.e. LBA48) is supported only in Mac OS 9 respectively
Mac OS X 10.2 onward, this property does only effect Mac OS X, specifically the
KeyLargoATA.kext, which communicates directly with the KeyLargo ATA chip. This
chip, wich is used in all Appler Power Mac G4 desktops with AGP does support
LBA48 regardless of the Open Firmware property, but the Open Firmware needs to
be LBA48-aware in order to boot from partitions (volumes) exceeding the first
137 GB.
Result: on Macs with the KeyLargo ATA chips (every Power Mac G4 with AGP)
LBA48 is always possible AFTER Mac OS X has started (10.2 and newer). On Power
Macs newer and including the Quicksilver 2002 (Rev. B mainboard) the Open
Firmware is also aware of the LBA48 capability and enables booting from a
larger than/exceeding 137 GB first volume.
http://support.apple.com/kb/HT2544
http://www.sonnettech.com/support/techtips/temporaid133.html
Note: Mac OS 9 supports only partition sizes up to 200 GB (Apple) or 190 GB
(Sonnet). (Which one is right?)
Cheers,
Andreas aka Mac User #330250
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You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs.
The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml
To post to this group, send email to g3-5-list@googlegroups.com
For more options, visit this group at http://groups.google.com/group/g3-5-list
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