To:         schlipper
From:       Strang
Subject:    1520 kickers
Date sent:  03/14/89 12:17 PM
Copies:     snow;bailey


Lou,

As you requested, here's a couple of 1520 kicker ideas.  They're a little odd, but the best I came up with.  I skipped all the obvious stuff, like supporting EGA or VGA display on the screen, changing the keyboard, etc.

1) Put that little bitty Antelope hard disk drive in a 1500 battery hole expansion cartridge, with a controller.  It would be a removable hard disk of sorts, even if it were in an odd place.  The functional fit is best with dual floppy systems, but it could be used for fast backup or sensitive data storage on systems with a built in hard disk.  The controller would have to be switchable to a secondary address space, to avoid conflict with the internal hard disk controller, and it would take some sort of special BIOS support for two hard disk controllers.

2) Add an extra internal power storage device (probably a capacitor, though maybe a fast drain battery) that could power the machine for about 30 to 60 seconds when other power went away.  This would give the user a last gasp chance to save his work when regular battery power dies.  It would reduce the user's level of worry about how accurate the low battery light timing is.  It would serve as a short duration UPS (Uninterruptable Power Supply), when there is not a battery in the battery hole.  Since most power outages are under 2 seconds, it would satisfy most UPS needs.  It would allow changing batteries without having to save your work, power the computer down and back up, and restart whatever you were working on, reducing the interruption in the thinking process.  Think of it as analogous to the small emergency air supply that scuba divers carry.  It would have to charge up from the main power source (battery or the AC supply), though ideally it would continue to carry most of it's charge while the computer was turned off, so it would not need to be recharged every time the computer was turned on.  There would need to be some visual or audable indication when the computer was operating on it's "last gasp" power.

This actually could be a good feature for future GRiD computers also.  Guessing when the end of a betteries charge is can be a frustrating game.  I have more than once lost data when I was working with my hard disk spun down, then my battery got low and turned out not to have enough charge left to spin my hard disk back up.

3) Develop an operating system extension or (preferably) a firmware extension that could quickly save the contents of memory and the entire processor and support hardware status to the hard disk, then could later quickly restore all that, so whatever was running before the save would again be running after the restore, continuing from where it was when saved.  This would allow the user to save exactly where he was, including the programs being run and the files in use, then pick up again in exactly the same place the next time he turned the computer on.  This idea could allow the user to very quickly restore into applications that take a long time to boot normally (like UNIX or FAST), which would be useful in demo situations.  Combined cleverly with idea 2 above, it would allow the computer to automatically save whatever was running when power was lost, even though the user was not around when power was lost.

There are several hard things in implementing this idea.  First, saving the complete hardware status of the computer involves a bunch of things besides the procesor and memory.  Some of them may be difficult or impossible to save.  Second, a piece of hard disk big enough to hold all the RAM on the computer and some other stuff would probably have to be permanently reserved for this use.  Third, making it work with non-MSDOS operating systems, like UNIX, might be prohibitively difficult.

Will