On Thu, Apr 22, 2004 at 10:50:57PM +0800, John Niven wrote: > Yes I have seen that connector which gave me the idea of using > two internal drives, one off each MB SCSI controller.
You can connect seven devices to each bus, may they be internal or external. Just pick up a SCSI cable with a suitable number of connectors. term <-> internal 2 <-> internal 1 <-> internal 3 <-> mainboard. > If Mainboard 2 also has termination haven't I got too many terminators? If the mainboard has a terminator, it is to electrically isolate each bus. If not, it doesn't matter (that is what the rambling in the last message was about). > What happens in Macs that have a SCSI CDROM and an IDE HardDrive? The busses are independent. If I recall correctly, the IDE bus is seen as a separate SCSI bus by software but I don't know how the boot ROM would see it nor how you would select a boot device while it is booting. > I am currently running it (in the Q950) without a terminator, and with > Term power off. The drive probably provides termination. Termination power is useful, but it won't matter very much if you only have one device on a short bus. > I works fine except, when I have my JackHammer NuBus SCSI card plugged > in I cannot boot from a CDROM. When I remove the JackHammer it will > boot. I'm very confused! > > That's one of the reasons I was considering ditching the JackHammer and > using the dual MB interfaces instead. The Q950 can handle up to 14 devices on the two busses, in any combination of internal and external. Just don't put more than 7 devices on each bus. Very few users require more than one bus. Those who do typically require extra performance (which I believe is the point of the JackHammer), have several devices which are hardwired to one or two SCSI IDs, or have a big file server with lots of redundancy. There are some issues which you may be running into: the computer may only be looking for the CD drive on a particular bus or busses during boot up. If I recall correctly, System 7.1 (and earlier) merge the two busses into one (I'm not sure how SCSI IDs work here). Byron. -- Vintage Macs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> Vintage Macs list info: <http://lowendmac.com/lists/vintagemacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/vintage.macs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
