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                 Inter-Office Memorandum

    To           Dorado project                                Date         April 21, 1980

    From         Ed Taft                                       Location     PARC/CSL

    Subject      Dorado booting-operation and mechanisms       File         [Ivy]LoadMB Mesa.MB
This loads the Dorado's control store with the contents of Mesa.MB and then starts it. That
microcode (since it is a standard emulator) in turn loads and starts the Alto OS from disk partition
1, the default partition for Mesa.
This means of loading microcode isn't very interesting for bootstrapping the standard emulators,
since the 3-push boot is easier and doesn't require the new microcode to be on your Dorado's disk.
But it is useful for loading non-standard or experimental emulators. (The LoadMB program has
some other features, described in section 3. The program is stored as [Ivy]Midas
Midas first displays a menu of the serial numbers of all the Dorados that are connected to this Alto.
Select your Dorado by positioning the cursor over your Dorado's serial number and clicking RED
(left or top mouse button). This step is skipped automatically if there is only one Dorado connected
to the Alto.
If the selected Dorado is running, Midas displays a status of "Running" and puts up a menu (near
the bottom of the screen) consisting of ABORT and DTACH items only. To halt the Dorado, select

Now Midas displays a large menu near the bottom of the screen. Select RUN-PROGRAM, and the
menu changes to a list of microprograms that you can run; these include CEDAR, LISP, MESA, and
SMALLTALK. Select one of those. The screen then goes blank while Midas loads the Dorado's
control store, a process that takes about a minute. After that, Midas starts the Dorado as if you had
initiated a 2-push boot.
Important: Do not leave Midas running on the Alto after you have loaded your microcode, because 2-,
3-, and 4-push boots from the Dorado's keyboard don't work if Midas is controlling the Dorado.
Therefore, exit Midas using SHIFT-SWAT (hold down the left SHIFT key and press the SWAT key,
which is the blank key to the right of right SHIFT).
The versions of emulator microcode stored on the Midas Alto's disk might not always be up-to-date.
If you are in doubt, update the microcode files by issuing the Executive command:
which runs FTP to retrieve the current versions of all emulator microcode.
Dorado booting-operation and mechanisms                                                            4

Machine status
There is a green light on the front panel of the Dorado that indicates the machine's present state, as
    1 flash.      Bootstrap sequence in progress (power-on or 3-push boot).
    2 flashes.    Bootstrap sequence failed.
    3 flashes. Transient power-supply problem-voltage or current was out-of-spec at least
    once since the last boot.
    4 flashes.    Present power-supply problem.
    S flashes.    Dorado has been shut down by 4-push boot
    6 flashes.    Dorado has overheated and shut itself down automatically.
    7 flashes.    Midas has taken over control of the Dorado.
    Continuously on. Bootstrap sequence is believed to have completed successfully, and there
    have been no occurrences of problems indicated by 3 through 7 flashes.
    Continuously off. Unknown but probably serious malfunction, or AC power turned off.

2. How it works
The Dorado contains a microcomputer that performs several functions, including monitoring power
and temperature, turning on and off the main power supplies and the disk driv~, and initiating
bootstrap sequences. The microcomputer can sense the state of the boot button, and it controls the
green light. This microcomputer and attendant EProms and other logic are mounted on the
BaseBoard, the bottom logic board in the machine.
A I-push boot is handled entirely by the Dorado microcode itself, with no action by the BaseBoard.
Multiple-push and power-on boots are handled by the BaseBoard. A 3-push or power-on boot
involves the following multiple-step sequence.

Loading Bootstrap microcode
The BaseBoard first halts the Dorado, issues an 1/0 reset, and resets or disables conditions that
could interfere with initial bootstrapping (Hold, Fault task wakeup). It then forcibly loads into the
Dorado's control store a small (-50 instruction) microprogram called Bootstrap. Finally, it starts the
Dorado executing this microprogram.
Loading of Dorado microcode in this manner is very slow; therefore, the amount of microcode in
Bootstrap is kept as small as possible.

Loading Initial microcode
Next, the Bootstrap microprogram and the BaseBoard microcomputer cooperate to load into the
Dorado's control store a somewhat larger (-700 instruction) microprogram called Initial. Initial is
stored as data in the BaseBoard's EProm. It is read by the microcomputer and handed to the
Dorado (via CPReg) at relatively high speed; the Boostrap microprogram copies this data into the
Dorado's control store.
When this operation is finished, the Boostrap microprogram gives control to the Initial
microprogram it has loaded. Bootstrap and Initial are arranged to occupy disjoint regions of the
control store. The BaseBoard then waits for the Dorado to complete the next step.
Dorado booting-operation and mechanisms                                                                 5

Initial execution
Initial performs a number of operations. First, it does a more thorough initialization of the Dorado.
It corrects parity in all registers and memories. It initializes the memory system (cache, map, and
storage) and puts it into a usable state. Finally, it notifies the BaseBoard that this step has been
completed successfully. (This notificatioJ:?, causes the BaseBoard to tum the green light continuously
on. If this event fails to occur within a reasonable time, the BaseBoard switches to the 2-flash
Second, Initial enables the I/O tasks that it requires (Display, Ethernet, and Junk tasks). It then
reads the keyboard in order to determine which emulator microcode to bootstrap.
Third, Initial makes contact with an Ethernet boot server (located in a Gateway or IFS system) and
requests it to supply the selected emulator microcode. That microcode is transferred over the
Ethernet and stored in the Dorado's main memory. (This step employs the Pup Microcode Boot
protocol, which is also used for booting DOs and is documented in [Maxc]

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