maddie@pnet01.UUCP (11/02/87)
Anyone out there know what the maximum Hard-Disk size is on the Mac before
you have to partition? For some reason 4 gigabytes seems to pop into my head,
can anyone tell me for certain?
UUCP: {cbosgd, hplabs!hp-sdd, sdcsvax, nosc}!crash!pnet01!maddie
ARPA: crash!pnet01!maddie@nosc.mil
INET: maddie@pnet01.CTS.COMroberts@cognos.uucp (Robert Stanley) (11/05/87)
In article <1939@crash.CTS.COM> maddie@pnet01.UUCP writes: > Anyone out there know what the maximum Hard-Disk size is on the Mac before >you have to partition? For some reason 4 gigabytes seems to pop into my head, >can anyone tell me for certain? I don't know the real answer, because I can't afford individual disks in the gigabyte range :-). However, 4 gig is 2^^32, or the largest binary integer value (unsigned), that can be stored in a 32-bit field. For a variety of reasons it is moderately unlikely that a larger field will be used, nor is it likely to matter in the reasonable future. The question is, might it be a smaller field? At present, the Mac could reasonably be described as having a 24-bit architecture, at least with respect to operating system stuff. So saying, the lower limit would be 2^^24, or 16 meg, but we can readily see that the actual limit is greater than this. Who among us remembers when the industry standard high-end disk was 29.5 Meg? So saying, chances are good that a 32-bit field controls the number in question, which gives 4G (unsigned) or 2G (signed). I know, who would ever want a signed value for maximum disk capacity, but stranger things can be observed in any operating system... Now, we are all agog to hear *why* you need to know. Warning: the foregoing, while reasonable, must be considered as speculation and not as fact. Robert_S -- Robert Stanley Cognos Incorporated S-mail: P.O. Box 9707 Voice: (613) 738-1440 (Research: there are 2!) 3755 Riverside Drive FAX: (613) 738-0002 Compuserve: 76174,3024 Ottawa, Ontario uucp: decvax!utzoo!dciem!nrcaer!cognos!roberts CANADA K1G 3Z4
brad@ut-sally.UUCP (blumenthal @ home with the armadillos) (11/10/87)
>In article <1939@crash.CTS.COM> maddie@pnet01.UUCP writes: > >> Anyone out there know what the maximum Hard-Disk size is on the Mac before In article <1720@cognos.UUCP> roberts@cognos.UUCP (Robert Stanley) writes: >24-bit architecture, at least with respect to operating system stuff. So >saying, the lower limit would be 2^^24, or 16 meg, but we can readily see that > >So saying, chances are good that a 32-bit field controls the number in >question, which gives 4G (unsigned) or 2G (signed). I know, who would ever > >Now, we are all agog to hear *why* you need to know. Heck, I'm a lisp hacker. I can think of ways of using a few gig of VM, not to mention a few gig of file space for my knowledge base :-). As long as we're going off into the wild blue yonder, I have a question. Isn't 2^n (where n is 24 or 32) just the number of addresses? HD's aren't usually byte addressable are they? more like 512 bytes/address? So this gives from 8 gig to about 2 terabytes (had to look that prefix up in my CRC) of addressable storage. When Jasmine comes out with one for under 2K, I'll buy it :-) Take care, brad
keith@apple.UUCP (Keith Rollin) (11/12/87)
In article <1720@cognos.UUCP> roberts@cognos.UUCP (Robert Stanley) writes: >In article <1939@crash.CTS.COM> maddie@pnet01.UUCP writes: > >> Anyone out there know what the maximum Hard-Disk size is on the Mac before >>you have to partition? For some reason 4 gigabytes seems to pop into my head, >>can anyone tell me for certain? > >I don't know the real answer, because I can't afford individual disks in the >gigabyte range :-). However, 4 gig is 2^^32, or the largest binary integer >value (unsigned), that can be stored in a 32-bit field. For a variety of >reasons it is moderately unlikely that a larger field will be used, nor is it >likely to matter in the reasonable future. The question is, might it be a >smaller field? At present, the Mac could reasonably be described as having a >24-bit architecture, at least with respect to operating system stuff. So >saying, the lower limit would be 2^^24, or 16 meg, but we can readily see that >the actual limit is greater than this. Who among us remembers when the >industry standard high-end disk was 29.5 Meg? > >So saying, chances are good that a 32-bit field controls the number in >question, which gives 4G (unsigned) or 2G (signed). I know, who would ever >want a signed value for maximum disk capacity, but stranger things can be >observed in any operating system... > Actually, I think that the maximum FILE size is set at 2G, cause it treats the long word that holds its size as signed. Don't ask me why, that just what I heard. However, I haven't had a chance to try it out :-) When I first saw this question, I responded that I thought the the upper limit of a hard disk was something like a longword number of 32Meg segments. Well, that may be technically correct, but is realistically unfeasible. As I glean it from IM, there is a maximum of 65535 "Allocation Blocks" on a Macintosh volume. With 512 byte blocks, this leaves you at 32M. However, each allocation block can be a variable length, as long as it's a multiple of 512 bytes. This size is refered to as the allocation block size, and is stored as a long word. So, while you may be able to have a drive with a 2^17 Terrabyte capacity (I think that's what it comes to), the minimum size of any files would be 4 gigabytes!