There are several tiny hidden partitions at the physical start of the drive. These occupy only a few MB, and are reserved for system use. People have noted that they actually cannot use an exactly 8GB partition, but have to enter a slightly smaller number such as 7.95GB. This is why - the missing megabytes are consumed by these tiny hidden partitions.
The 8GB limit is because the system calls hard-wired into the 'old world' ROMs can only address physical addresses up to 8GB. If your system tries to use the ROMs to access memory beyond the physical 8GB address space, there is an error. 'New World' machines copy the ROM memory into RAM at bootup, and the entire ROM call mechanism is executed in software, so the only address space limitation is the addressing capability of the CPU. I'm not sure exactly how it does it, but if you look at the XPostFacto 'verbose' startup messages, you will see a line: 'emulating New World ROMs'. The fact that Wallstreets are able to run OS-X in large partitions, means that the at least some part of the ROM call mechanism has been patched to bypass the 8GB addressing limitation. Perhaps someone more knowledgeable could clarify this? hth.. Alan ================================================ On 2009-11-01 12:18 -0400, John Ruschmeyer wrote: >Alan, > >Any possibility of summarizing what the partition map looks like? In >particular, is MacOS 9 installed on the helper partition or the large one >where OS X lives? > >How about a quick HOWTO? > >Thanks... >John > > >On 11/1/09 9:36 AM, "classical" <[email protected]> wrote: > >>> The 8GB limit still applies, XPostFacto creates a tiny boot partition >>> (Much less than 8GB !!) as the first partition and uses this as a helper >>> partition to boot the OS. so you are still starting the boot from a <8GB >>> partition, but it is a hidden partition.... >> >> You are technically quite correct at the 'nuts and bolts' level, but >> on the other hand, once startup has completed via XPostFacto, the >> computer 'believes' it has completed the entire boot sequence from >> the volume where OS-X is installed. >> >> I am trying to dispel the notion that Wallstreets can only run OS-X >> from a partition of less than 8GB. >> >> ..Alan > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Books, a group for those using G3 iBooks and PowerBooks (we run a separate list for G4 'Books). The list FAQ is at http://lowendmac.com/lists/g-books.html 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/g-books Support for older Macs: http://lowendmac.com/services/ -~----------~----~----~----~------~----~------~--~---
