RIP Optane/XPoint

By: rwessel (rwessel.delete@this.yahoo.com), July 31, 2022 5:33 am
Room: Moderated Discussions
Doug S (foo.delete@this.bar.bar) on July 30, 2022 10:43 pm wrote:
> David Hess (davidwhess.delete@this.gmail.com) on July 30, 2022 3:44 pm wrote:
> > David Hess (davidwhess.delete@this.gmail.com) on July 29, 2022 8:59 pm wrote:
> > > Linus Torvalds (torvalds.delete@this.linux-foundation.org) on July 29, 2022 11:20 am wrote:
> > > >
> > > > You simply don't want a situation where all your memory is your long-term image. The whole "if
> > > > you lose power, you reboot and just continue" thing is mindless blathering. Exactly because it
> > > > makes a fundamental mistake in assuming that everything is always perfect and bug-free.
> > >
> > > I have developed small embedded systems which could do that with critical state stored in either EEPROM
> > > or CMOS SRAM with backup power. Some old test instrumentation used battery backed up SRAM as main memory,
> > > and would pick up exactly where it lost power, but I do not think that would be practical now at least
> > > in that way. At the time, common CMOS SRAM was fast enough to be treated as main memory.
> > >
> > > It is not quite the same thing, but I have done some application programming where it was
> > > convenient to keep state on mass storage which allowed the program to be modified and then
> > > restarted without interrupting operation. This required an entire section of code for loading
> > > external state at startup, and then continuously updating state as required.
> >
> > Last night I remembered another computer system which could start up exactly where it
> > left off after power loss; this was a feature of some systems which used core memory.
> > It was a small step from relying on core memory for program and data storage, to including
> > circuits to safely shut down and restart after power loss by saving CPU state.
> >
> > This could also have been done with a microprocessor and CMOS SRAM or even DRAM, but
> > I do not remember any systems which did it that way. Someone must have though.
>
>
> This is before my time but in the core memory days booting was kind of a pain
> in the ass, was it not? Even if you had the luxury of a hard drive you probably
> had to either toggle in a bootloader or load it via paper tape.
>
> That was probably the main reason that was used, not necessarily because they wanted to pick up where
> they left off - but if the PC, SP and registers were themselves stored in a type of core memory (or
> there was a big capacitor or something allowing a split second for them to be saved to core memory)
> then I guess theoretically it could simply pick up where it left off once power returns.


At least larger systems usually had ways to initiate an I/O to (at least some) I/O devices to loading the bootstrap program.

For example, on any* S/360, you'd select an I/O device (often a set of three hex dials), and then pushing the load button would get the machine to send a read command to the selected I/O device, with the target address set to zero. That was actually the standard rad command (cards, tape), or defined as "read-IPL" for things like disk (where it would seek to track zero, head zero, and read the first record on the track). Other I/O could be chained to that. After that, the PSW would be loaded from the area read into, and away you went. Still works that way (although now there are some additional options - you can boot from a SCSI/FC device).

Other large systems were similar. The standard 1401, for example, had a "tape load" button that would load data from the first tape drive into low core. There was a way to do that from the card reader as well, and I seem to recall that was eventually a way to do that from disk.

Older machines, and some smaller ones, often did require manual bootstrapping.

*At least anything in the mainstream.
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TopicPosted ByDate
RIP Optane/XPointWes Felter2022/07/28 07:53 PM
  RIP Optane/XPointRayla2022/07/28 08:28 PM
  RIP Optane/XPointDoug S2022/07/28 09:00 PM
    RIP Optane/XPointNoSpammer2022/07/29 01:50 AM
    NVDIMM-NEric L2022/07/29 03:36 AM
    RIP Optane/XPointMichael S2022/07/29 04:02 AM
      RIP Optane/XPointDoug S2022/07/29 10:40 AM
        RIP Optane/XPointDoug S2022/07/29 10:43 AM
          RIP Optane/XPointLinus Torvalds2022/07/29 11:20 AM
            RIP Optane/XPointDavid Hess2022/07/29 08:59 PM
              RIP Optane/XPointDavid Hess2022/07/30 03:44 PM
                RIP Optane/XPointDoug S2022/07/30 10:43 PM
                  RIP Optane/XPointrwessel2022/07/31 05:33 AM
                  RIP Optane/XPointKonrad Schwarz2022/08/02 08:06 AM
                  RIP Optane/XPointDavid Hess2022/08/02 10:24 PM
                    RIP Optane/XPointDavid Hess2022/08/02 10:26 PM
                    RIP Optane/XPointAdrian2022/08/03 01:19 AM
        RIP Optane/XPointanonymou52022/07/29 12:50 PM
    RIP Optane/XPointGionatan Danti2022/07/29 09:09 AM
    RIP Optane/XPointMark Roulo2022/07/29 10:02 AM
      RIP Optane/XPointdmcq2022/07/30 03:42 AM
      RIP Optane/XPointanon32022/07/31 10:19 PM
        RIP Optane/XPointanon22022/07/31 10:55 PM
          RIP Optane/XPointDoug S2022/08/01 08:37 AM
            RIP Optane/XPointGionatan Danti2022/08/01 01:33 PM
              RIP Optane/XPointNoSpammer2022/08/02 03:50 AM
                RIP Optane/XPointDoug S2022/08/02 09:24 AM
                  RIP Optane/XPointGionatan Danti2022/08/02 10:34 AM
                  RIP Optane/XPoint---2022/08/02 10:39 AM
            RIP Optane/XPointDavid Hess2022/08/03 03:48 AM
              RIP Optane/XPointMichael S2022/08/03 06:04 AM
                RIP Optane/XPointDavid Hess2022/08/03 08:56 AM
        RIP Optane/XPointAdrian2022/08/01 02:15 AM
          RIP Optane/XPointGionatan Danti2022/08/01 06:07 AM
            Losses vs not profitable enoughMark Roulo2022/08/01 10:15 AM
              Losses vs not profitable enoughdmcq2022/08/01 11:50 AM
                Losses vs not profitable enoughGionatan Danti2022/08/01 12:34 PM
            RIP Optane/XPointMichael S2022/08/01 02:47 PM
              RIP Optane/XPointAnon2022/08/01 03:09 PM
                RIP Optane/XPointMichael S2022/08/01 03:32 PM
      RIP Optane/XPointGroo2022/08/01 12:28 PM
        RIP Optane/XPointanon32022/08/01 10:33 PM
          RIP Optane/XPointGroo2022/08/03 11:15 AM
            RIP Optane/XPoint---2022/08/03 03:05 PM
    LatencyDavid Kanter2022/07/29 06:35 PM
  Operating system and driver overheadEric L2022/07/29 03:44 AM
    Operating system and driver overheadLinus Torvalds2022/07/29 10:45 AM
  altrernatives?Michael S2022/07/29 05:17 AM
    altrernatives?Rayla2022/07/29 06:49 AM
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