dave@onfcanim.UUCP (Dave Martindale) (01/12/86)
You could actually boot from DECtape. The real challenge was getting a minimal root filesytem (bootloader, some inodes, unix, /etc/init, /bin/sh, and some of /dev) onto a DECtape. If I remember correctly, they only stored about 256Kb. Speaking of strange DEC hardware, anyone remember the RF11 disk? A fixed- head drive that was formatted so you could rewrite individual 16-bit words, and whose transfer rate was *slower* than the not-exactly-fast RK05 disk. It made a good /tmp though (zero seek time).
jdb@mordor.UUCP (John Bruner) (01/20/86)
In article <14775@onfcanim.UUCP> dave@onfcanim.UUCP (Dave Martindale) writes: >You could actually boot from DECtape. The real challenge was getting a >minimal root filesytem (bootloader, some inodes, unix, /etc/init, /bin/sh, >and some of /dev) onto a DECtape. If I remember correctly, they only >stored about 256Kb. When I was looking after an 11/45 I kept a set of standalone utilities on a (tp-format) DECtape. When you created a tape with "tp" it would put "/usr/mdec/tboot" or "/usr/mdec/mboot" (depending upon whether it was a DECtape or magtape) into block 0. This single-block bootstrap knew how to read tp-format files. This DECtape saved me a lot of trouble once. Our root filesystem was located in the center of a CDC 9766 disc. Since we had no hardware bootstrap for the SI 9400 controller, we booted the disc by toggling a read command in on the front panel with the disc write-protected. Unfortunately, during one reboot someone neglected to write-protect the disc and toggled in a 64Kb write instead of a read. We lost the first disc partition but I was still able to boot using my handy DECtape. Our magtapes were completely unreliable, so I also did kernel crash dumps onto DECtape. An 11/45's 256Kb fits quite comfortably. -- John Bruner (S-1 Project, Lawrence Livermore National Laboratory) MILNET: jdb@mordor [jdb@s1-c.ARPA] (415) 422-0758 UUCP: ...!ucbvax!dual!mordor!jdb ...!seismo!mordor!jdb