---------- Original message ---------- Subject: Re: Using HD > 128GB in G4 Macs! Date: Wednesday, 06. April 2011 From: Paul Stamsen <[email protected]> To: [email protected] > Previously, at 8:22 PM +0200 4/6/11, as Mac User #330250 so eloquently > wrote: (snip) > > >> The chief danger in that script is that if you do an OF reset you > >> will lose access to the part of the drive above 128Gb until you > >> re-activate the script. > > Sorry, I missed that. How again?
If you loose the LBA48 property Mac OS X will no longer be able to access beyond 128 GB. This is only dangerous if a partition starts before that limit and extends beyond this limit. How do you loose the LBA48 property? 1.) By zapping the NVRAM (pressing Opt-Cmd-N-V at the chime right after turning on your Mac). 2.) By resetting everything in Open Firmware. http://support.apple.com/kb/ht1379 3.) When your PRAM battery is weak it won't hold the information stored in NVRAM (time, start-up volume, LBA48-property, …)- 4.) When replacing the PRAM battery. What is important when partitioning for a non-LBA48-Mac? A.) Which Macs are non-LBA48? All before the Quicksilver 2002. B.) On which Macs does the OF hack work? All that use KeyLargo IDE chips. 1.) Partitions that contain any (Mac) OS should end at the 128 GB limit. 2.) Partitions that contain Data should start at the 128 GB limit. 3.) NO PARTITION should start before 128 GB and extend beyond. This is the ONLY danger: If a parition starts before the 128 GB limit, say: at 120 GB, and this partition has a size of 100 GB, so from 120 to 220 GB, and you loose the LBA48 property, but then access this partition… 1.) Mac OS X will see the first 8 GB of this 100 GB parition. It will read the contents of this file system and try to read beyond, and WRITE beyond, because this is what the partition and its file system HFS+ tell Mac OS X to do. 2.) All read/write accesses beyond the 128 GB limit will be “wrapped”. So, if Mac OS X reads the 100 GB partition's HFS+ file system, and wants to read a file which is, say, at 20 GB inside this file system, hence at 140 GB of the physical disk, this read/write call will be wrapped to the 140-128= physical 12 GB position of the drive. So you will corrupt the data of the first partitition. This very likely render your system unbootable some day! I hope this isn't too complicated. (I tend to write too much.) Just remember this: Using the LBA48 property on a Mac that doesn't support it (without hacking), ALWAYS end and start your paritions at 128 GB! Because then it won't see anything at all of the partition that extends beyond this limit, and so it cannot write-wrap anything, thus data corruption is not possible. Yes? Cheers, Andreas aka Mac User #330250 -- 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 [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list
