dave@PRC.Unisys.COM (David Lee Matuszek) (01/09/91)
I have two Macintoshes and one 80MB hard drive. I'd like to access the HD from either Mac. I understand I can put the HD on an Apple network if I make one of the Macs a dedicated server. Um, kinda misses the point, I think. Does anybody have a reasonable way to share one hard drive between two Macs? Or is this just not technically feasible? -- Dave Matuszek (dave@prc.unisys.com) -- Unisys Corp. / Paoli Research Center / PO Box 517 / Paoli PA 19301 -- Any resemblance between my opinions and those of my employer is improbable. < You can put a mouse on an IBM. And you can put a radio on a motorcycle. >
cheshire@Neon.Stanford.EDU (Stuart David Cheshire) (01/10/91)
In article <16073@burdvax.PRC.Unisys.COM> dave@PRC.Unisys.COM (David Lee Matuszek) writes: >I have two Macintoshes and one 80MB hard drive. I'd like to access >the HD from either Mac. I understand I can put the HD on an Apple >network if I make one of the Macs a dedicated server. Um, kinda >misses the point, I think. Use SingleShare, it's just like Appleshare, except non-dedicated. It will slow down the Mac with the hard disk, take up memory, and you'd better be careful not to run too many flakey INITs because if you crash the machine you screw up the other person's work too. Also, sharing a HD across LocalTalk is painfully slow. Ethernet helps, but from what I've heard, it doesn't help as much as it should -- it's still a lot slower than having your own hard disk. Stuart Cheshire (cheshire@cs.stanford.edu)
wcarroll@encore.com (Mr. New Dad) (01/11/91)
From dave@PRC.Unisys.COM (David Lee Matuszek): > I have two Macintoshes and one 80MB hard drive. I'd like to access > the HD from either Mac. I understand I can put the HD on an Apple > network if I make one of the Macs a dedicated server. Um, kinda > misses the point, I think. > > Does anybody have a reasonable way to share one hard drive between > two Macs? Or is this just not technically feasible? We've had lots of suggestions, but they all seem to imply something like: ------ | HD | ------ comm link | ---------------- | | | ------- ------- | Mac | | Mac | ------- ------- Is it possible to do this? ------ | HD | ------ | ----------------- <- scsi bus | | ------- ------- | Mac | | Mac | ------- ------- Has anyone ever seen it work? What kind of problems were encountered? How were they resolved? -- William R. Carroll (Encore Computer Corp., Ft. Lauderdale FL) wcarroll@encore.com uunet!gould!wcarroll "This comment without commentary is not the view of the staff or management of WKPX, the Broward County School Board, ... or even me." - KZ
whit@milton.u.washington.edu (John Whitmore) (01/11/91)
In article <130402@jake.encore.com> wcarroll@encore.com (Mr. New Dad) writes: >From dave@PRC.Unisys.COM (David Lee Matuszek): >> Does anybody have a reasonable way to share one hard drive between >> two Macs? Or is this just not technically feasible? >Is it possible to do this? > ------ > | HD | > ------ > | > ----------------- <- scsi bus > | | > ------- ------- > | Mac | | Mac | > ------- ------- This has the problem that two devices on the bus have the same SCSI address. The two Macintoshes are both device #7; short of rewriting ALL the driver software (including the bootup code in the ROM), it is probably impossible to make this scheme work. The simplest workable solution would use a SCSI bridge (i.e. a special-purpose SCSI box with two separate SCSI bus ports). I don't know of any such devices available at reasonable cost. I recall that Traveling Software was considering building one some years ago, but haven't heard if their project was ever marketed. John Whitmore
tj@kona.cs.ucla.edu (Tom Johnson) (01/12/91)
In article <130426@jake.encore.com> mjw@encore.com (Mike Willegal) writes: > >On the other hand it probably would be an easy hack to change the ID in >the driver, if you had a little time. Actually the SCSI ID of the macintosh is stored in the Parameter Ram. If you feel particularly adventurous and want to look for yourself, try the following Think C 4.0 code: ----cut here---- pascal void ReadXPram() = {0x201F,0x205F,0xA051}; pascal void WriteXPram() = {0x201F,0x205F,0xA052}; main() { char DelayByte,SCSIid,delayedDrive; ReadXPram(&DelayByte, 0x01,1); ReadXPram(&SCSIid,0x02,1); ReadXPram(&delayedDrive,0x03,1); } ----and here---- ReadXPram and WriteXPram each take a ptr to the variable, the location of the value to be read and the number of bytes to read. I was playing around with this when we got a couple of 330Mg Wren VI drives which don't spin up very quickly--we had internal Quantom 170Mg drives in the machines (the Wrens were external, of course) and we found we couldn't startup from the Wren from a cold start if both machines had System Folders. We set the Wren as the startup device, but the mac would time out before the Wren was ready to go, so it would only boot off of the Quantom. I changed the DelayByte to 0xC8 and the delayedDrive to the SCSI ID of the Wren and it worked fine--the mac waited long enough for the Wren to get running. My source told me of the Mac SCSIid location just as a curiosity. Have fun, but be aware that I don't take any responsibility for what you do to your poor macs and drives when you change the scsi ids!!! Tom -- Tom Johnson UCLA Computer Science Department 3413 Boelter Hall, Los Angeles CA 90024 (213)825-2145 Internet: tj@cs.ucla.edu
siegman@sierra.STANFORD.EDU (siegman) (01/12/91)
I know from nothing about this subject, but is it conceivable to put two partitions on one HD, have each Mac access one of these, then have the two Macs publish to each other with TOPS?
time@tbomb.ice.com (Tim Endres) (01/12/91)
In article <130424@jake.encore.com>, mjw@encore.com (Mike Willegal) writes: > Now just format the disc into two paritions, run one mac on parition one and > the other on partition two. I don't know if you can boot directly off > the second partion of a disc, the second mac may have to boot off > some other device before mounting partition two. And be REAL SURE the driver you are using is smart enough to check the status of the bus before it goes off trying to do its stuff, otherwise the contention for the single bus may cause lost data. I know that a driver I wrote got burned by a busy bus once, and I ended up putting the proper checks in, but who knows with other drivers... tim. ------------------------------------------------------------- Tim Endres | time@ice.com ICE Engineering | uupsi!ice.com!time 8840 Main Street | Whitmore Lake MI. 48189 | (313) 449 8288
Bruce.Hoult@bbs.actrix.gen.nz (01/14/91)
Mr. New Dad (congrats!) writes: >Is it possible to do this? > > ------ > | HD | > ------ > | > ----------------- <- scsi bus > | | > ------- ------- > | Mac | | Mac | > ------- ------- Don't even *think* about it! This will be electrically bad for the bus, since both Macs will be on the same SCSI ID, and will both be trying to act as bus masters. Perhaps (?) worse: Macs cache certain disk sectors (especially directory stuff) internally and they are likely to get out of sync with each other. You really don't want to try this... -- Bruce.Hoult@bbs.actrix.gen.nz Twisted pair: +64 4 772 116 BIX: brucehoult Last Resort: PO Box 4145 Wellington, NZ "...a plan so cunning, you could pin a tail on it and call it a weasel..."
ifar355@ccwf.cc.utexas.edu (David H. Huang) (01/17/91)
In article <1991Jan14.141451.2957@actrix.gen.nz> Bruce.Hoult@bbs.actrix.gen.nz writes: [ is it possible to hook two macs up to one hd ] >Don't even *think* about it! This will be electrically bad for the bus, >since both Macs will be on the same SCSI ID, and will both be trying to >act as bus masters. Yeah, IMHO, Apple really screwed up with the Macintosh SCSI since it doesn't handle the arbitration correctly. Oh well... at least they got it right when designing the Apple II SCSI cards. >You really don't want to try this... >-- >Bruce.Hoult@bbs.actrix.gen.nz Twisted pair: +64 4 772 116 >BIX: brucehoult Last Resort: PO Box 4145 Wellington, NZ >"...a plan so cunning, you could pin a tail on it and call it a weasel..." -- David Huang | Internet: ifar355@ccwf.cc.utexas.edu | "My ganglion is stuck in UUCP: ...!ut-emx!ccwf.cc.utexas.edu!ifar355 | a piece of chewing gum!" America Online: DrWho29 |