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Which DECnet interfaces support remote, unattended, booting?

by bob＠jfcl.com

Johnny Billquist wrote: And on re-reading I see that I misunderstood the comment. Sorry - I left too many words out of the original comment. Gotta remember to be verbose :-) BTW, you are right - I just turned on my 11/83 it does have a "XH" boot in the ROM. I'm guessing that I could set that us as a default boot, and then as long as the DELQA knows enough MOP to force a bus INIT, it'll work. Bob

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by Paul_Koning＠Dell.com

On May 17, 2013, at 11:40 AM, Bob Armstrong wrote: Paul_Koning at Dell.com wrote: boot support doesn't make any sense in a software DDCMP implementation .... I was also wondering if, say, the DLV11 DDCMP driver in DECnet implemented booting. As you say, it's not as useful as an independent hardware boot in the controller, but it would work as long as enough of the OS is still alive to process DLV11 interrupts. You've got maybe a 50-50 chance, but even still - async DECnet was a low end solution so you expect low end results :-) The DDCMP driver wouldn't have to actually do the boot - there is a DECnet boot ROM for asynchronous interfaces already, and you could just assume that was already set up. All the DDCMP driver would have to do is start it. The problem here is that "Boot" has two very different meanings. Boot.1 == the process of forcing a running or halted CPU to reinitialize itself. Boot.2 == the process of loading the operating system or main software into a CPU. For example, boot.1 can be done on a PDP-11 by cycling the power. Boot.2 on a PDP-11 involves running the "boot loader" ROM code, which loads a small program from somewhere, which in turn loads a larger program... finally resulting in the system being fully operational. These two are independent in some sense (though the consequence of boot.1 is that boot.2 is initiated). MOP supports both of these. Boot.1 is performed by the MOP Boot message. Boot.2 is performed by the MOP Load messages. A system may support one or both or neither of these two MOP functions. For example, it might power up into a boot loader ROM that is configured to run MOP Load. (Terminal servers are examples of this.) If so, you might be able to force a restart by sending a MOP Boot message, or that may not be supported. Conversely, at least in theory, a system might support Boot.1, but what happens next is a boot from disk. The "boot support" I was discussing -- the one that requires hardware help -- is Boot.1. By definition it is intended to work when the CPU is not cooperating, so it must be executed in some external hardware, and that hardware has to have the ability to force the CPU to restart. As John Wilson pointed out, on a PDP11 that means yanking on the INIT line while shielding yourself from the consequences. Boot roms that support "DECnet boot" are implementations of Boot.2, i.e., MOP Load. paul

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bqt＠softjar.se

On 2013-05-17 17:43, Bob Armstrong wrote: Johnny Billquist wrote: Um, no. The "small program" is a program expected to be executed by the host. You missed my point - the issue was not "where does the small program execute from", it was "where is the code for the boot program stored (permanently) before it gets DMAed into the host". :-) Yes. My mistake. Johnny

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bqt＠softjar.se

On 2013-05-17 17:40, Johnny Billquist wrote: On 2013-05-17 17:34, Bob Armstrong wrote: John Wilson wrote: They DMA a small program into memory Ah, I was wondering about that, because there aren't any separate boot ROMs on the DEUNA. I bet the "small program" is just part of the T11 code. Um, no. The "small program" is a program expected to be executed by the host. And on re-reading I see that I misunderstood the comment. Yes, the program to DMA into the host is located along with all the other code on the controller (a T11 for the DEUNA, and a 68K for the DELUA). Johnny

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bob＠jfcl.com

Johnny Billquist wrote: Um, no. The "small program" is a program expected to be executed by the host. You missed my point - the issue was not "where does the small program execute from", it was "where is the code for the boot program stored (permanently) before it gets DMAed into the host". Bob

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bob＠jfcl.com

Paul_Koning at Dell.com wrote: boot support doesn't make any sense in a software DDCMP implementation .... I was also wondering if, say, the DLV11 DDCMP driver in DECnet implemented booting. As you say, it's not as useful as an independent hardware boot in the controller, but it would work as long as enough of the OS is still alive to process DLV11 interrupts. You've got maybe a 50-50 chance, but even still - async DECnet was a low end solution so you expect low end results :-) The DDCMP driver wouldn't have to actually do the boot - there is a DECnet boot ROM for asynchronous interfaces already, and you could just assume that was already set up. All the DDCMP driver would have to do is start it. Bob

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bqt＠softjar.se

On 2013-05-17 17:34, Bob Armstrong wrote: John Wilson wrote: this is a ridiculous security risk so that's why MOP had a magic number Yep, even the DMR has a boot "password", which is just an 8 bit value set by dip switches on the board, that has to match up with the MOP message. I don't remember how you set the password on the DEUNA/DELUA, it might be something you programmed, so by default it was a known value, but as soon as the system have started up, it can change it to something else, or even disable the trigger ability (maybe). They DMA a small program into memory Ah, I was wondering about that, because there aren't any separate boot ROMs on the DEUNA. I bet the "small program" is just part of the T11 code. Um, no. The "small program" is a program expected to be executed by the host. And I'm assuming that this scheme didn't work on any UNIBUS VAXes - only PDPs. Correct. :-) Johnny

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by Paul_Koning＠Dell.com

On May 17, 2013, at 11:34 AM, Bob Armstrong wrote: John Wilson wrote: this is a ridiculous security risk so that's why MOP had a magic number Yep, even the DMR has a boot "password", which is just an 8 bit value set by dip switches on the board, that has to match up with the MOP message. They DMA a small program into memory Ah, I was wondering about that, because there aren't any separate boot ROMs on the DEUNA. I bet the "small program" is just part of the T11 code. And I'm assuming that this scheme didn't work on any UNIBUS VAXes - only PDPs. That sounds right. The network interface needs a way to tell the machine to restart. On a VAX, the Unibus doesn't do that. In theory you could have a console front end processor that implements MOP Boot message handling and does the restart if it sees one. (The same would be true on PDP-10 or -20 machines that have a front end processor.) In practice, I don't remember that such a thing was ever done. paul

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bob＠jfcl.com

John Wilson wrote: this is a ridiculous security risk so that's why MOP had a magic number Yep, even the DMR has a boot "password", which is just an 8 bit value set by dip switches on the board, that has to match up with the MOP message. They DMA a small program into memory Ah, I was wondering about that, because there aren't any separate boot ROMs on the DEUNA. I bet the "small program" is just part of the T11 code. And I'm assuming that this scheme didn't work on any UNIBUS VAXes - only PDPs. Bob

12 years, 1 month

Which DECnet interfaces support remote, unattended, booting?

by bqt＠softjar.se

On 2013-05-17 17:18, John Wilson wrote: From: "Bob Armstrong" <bob at jfcl.com> I thought I remembered that the Ethernet interfaces could do it, but how does that work? Sneakily. It's in the DEUNA/DELUA manuals. They DMA a small program into memory, including the power fail vector (24/26 I think?) which points at it, and then fake a power failure while blocking INIT L to themselves. Obviously this is a ridiculous security risk (I guess they assumed the ethernet coax was physically secure) so that's why MOP had a magic number (which could be 0 in earlier versions but not in later revs). Your memory is way better than mine. :-) Thanks. That summary made me recall details. The DEQNA/DELQA were kludgier and I'm drawing a blank on whether they even support network-triggered booting. I think I remember seeing the DELQA being able to. The DEUNA/DELUA/DEQNA/DELQA has no reason to implement DDCMP, although it certainly had enough local CPU power to do so. Did it still scan for MOP trigger messages anyway? DEUNA/DELUA support MOP dump/load/sysID (as well as ECT echo) in firmware, I'm blanking on which parts of MOP the DELQA knows innately (I think at least enough to send system IDs), and the DEQNA is too mindless to do anything w/o driver help. :-) Johnny

12 years, 1 month

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