| A9M0106 3.5 drives daisy chaining and the boot sequence. [message #382511] |
Wed, 27 March 2019 18:08  |
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Originally posted by: Leon Sargent
Lets see if I have this correct... it has been a few decades.
I have two 3.5 drives daisy chained together. The drive connected to the smart port directly is the only drive I can boot from.
The second drive, daisy chained to the above is not able to boot as it would be drive 2?
So. Am I correct that Pr#5,s1 will boot with appropriate bootable floppy and pr#5,s2 will not boot in a daisy chained configuration?
They both seem to work when individually connected to the smart port with no daisy chaining...
I referenced this article from https://www.bigmessowires.com/2019/02/04/daisy-chain-daydrea ms/
Drive Ordering and Boot Limitations
A critical requirement is the ordering of drives in the daisy chain: the dumb 3.5 inch drives must appear before the smart drives, which must appear before the 5.25 inch drives. This requirement stems from the way the disk port’s control signals are multi-purposed to serve several different types of drives, where some types didn’t yet exist when the older types were designed. You can try physically connecting the drives in a different order, but some of them won’t work and may even be damaged.
The ordering requirements have the side-effect of constraining the computer’s options for boot disks. With complex daisy chains, these constraints can become inconvenient and annoying.
Dumb 3.5 inch drives and smart drives are placed in a single logical group that’s mapped to slot 5. Only the first drive in that group can be used as a slot 5 boot drive. If two dumb 3.5 inch drives are connected, only the first can be used to boot the computer. And if both a dumb 3.5 inch drive and a smart drive are connected, only the 3.5 inch drive can be used to boot the computer. The smart drive can never serve as a boot drive, in this case.
I thought the A9M0106 was the drive with the smarts and the Unidisk was the dumb one. As noted to in the above article from Bigmessowires
Leon
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