[comp.sys.mac] Share SCSI drive?

kuo@tramp.Colorado.EDU (Andy Y.A. Kuo) (08/12/89)

I recently read about someone successfully make two Mac share one SCSI
hard drive without any partition.

He also said that by partitioning the hard drive, he was able to 
make a AppleIIGS(ProDOS) use one partition while the Mac use the other
partition on the same drive without any problem. (he didn't mention IBM)

My problem is, how is this possible, why would the drive allow that?
Will this damage the hardware?

Appreciate any response!

-Andy

kaufman@neon.Stanford.EDU (Marc T. Kaufman) (08/12/89)

In article <10697@boulder.Colorado.EDU> kuo@tramp.Colorado.EDU (Andy Y.A. Kuo) writes:

>I recently read about someone successfully make two Mac share one SCSI
>hard drive without any partition.

Not without special software.  The standard SCSI driver automaticly assigns
the Mac as device 7, and there can be only one device 7 on a bus.

>He also said that by partitioning the hard drive, he was able to 
>make a AppleIIGS(ProDOS) use one partition while the Mac use the other
>partition on the same drive without any problem. (he didn't mention IBM)

Only if the drive is physically moved between the two machines (not
connected to both simultaneously).

>My problem is, how is this possible, why would the drive allow that?
>Will this damage the hardware?

No, it won't damage the hardware -- SCSI is designed to allow just that.
However, it won't work with the Apple supplied SCSI manager, because the
default manager does not perform the Bus Arbitration phase, and so will
probably mess up a transfer from the other computer at some point.

Marc Kaufman (kaufman@Neon.stanford.EDU)