keith@Apple.COM (Keith Rollin) (09/25/88)
Since this is a question that I'm sure everyone would like to hear the answer to, I've posted this to the net instead of replying personally. >Keith, > > When you have time, could you please describe how volume partitions >greater than 32 megs are now supported by GS/OS? Will I be able to access >these partitions from 8 bit ProDOS 1.5 if GS/OS is the primary OS underlay? >Cmments? PLEASE!!! hehehe Thanks for any assistance. > >Todd South GS/OS, per se, accesses all devices through device drivers. These drivers are either real RAM based drivers loaded from disk (like the UniDisk and SCSI card drivers), or 'generated drivers' which are RAM based drivers created on the fly to handle the ROM based drivers on peripheral cards that don't have their own drivers on disk (like the Profile). Therefore, all GS/OS does is ask for a specific block from the disk driver. Actually, it doesn't talk to the device drivers directly. It makes all of its filing requests through the File System Translators (FSTs). The FSTs take a generic request from GS/OS (like "get me bytes 1024-2047 from file Gibbley") and translates them into physical block I/O requests ("read blocks 624 and 456 and put them here"). The FSTs make these requests to the device drivers. GS/OS can handle volume and files sizes of up to 4 gigabytes. However, either the FSTs or device drivers can impose limits of their own along the way. For instance, the ProDOS FST cannot access files larger than 16Meg or volumes larger than 32Meg. The Apple 5.25" disk driver driver cannot read volumes larger than 143K. If an FST or device driver is asked to read something beyond its range, it pops back to GS/OS saying "No, way. block out of range!" So, you see, >32meg volumes are not really feasible yet under ProDOS FSTs. However, GS/OS can access larger volumes with the appropriate FSTs and drivers. For instance, the High Sierra FST will read CD-ROM drives up to their full size of something like 550 Meg. On the other hand, if you were to partition an HD-80SC into 2 volumes of 40Meg, only the first 32Meg would be available under ProDOS. ProDOS 8 an entirely separate issue, however. ProDOS 8 is still the same old ProDOS that we all grew up with on our Apple //e's c's and pluses. It is (almost) entirely separated from ProDOS 16 and GS/OS. Therefore, no benefit is gained in ProDOS from GS/OS, as GS/OS is NOT the "underlying operating system" of ProDOS 8. As a matter of fact, on previous system disks, it was the other way around; ProDOS 8 was the underlying operating system for ProDOS 16. I hope that this answers your (and others's) questions! Keith Rollin amdahl\ Developer Technical Support pyramid!sun !apple!keith Apple Computer decwrl/ "You can do what you want to me, but leave my computer alone!"