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Olivetti AT&T PC6300 PC1050 Bare Motherboard

MicroCoreLabs

MicroCoreLabs

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I have a PC1050 with 5V, 12V, and -12V connected to a bench supply and I was wondering if there was supposed to be a beep if it runs/comnpletes some of its POST.

I get around 3 Amps on the 5V rail and practically nothing on the 12V rails.

I needed to tie the READY line high at the 8087 to get the 8086 to execute instructions. Seems that they should've had a pull-up on this signal...

I can see lots of bus cycles at the 8086 and the EPROMs, but I dont have anything other than this motherboard so I cant tell if it is executing normally or not.

Is it supposed to beep at any point in the boot/POST code? Or do I need more stuff hooked up before it progresses to a point where it beeps?


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MicroCoreLabs said:
Olivetti AT&T PC6300 PC1050 Bare Motherboard
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So, Olivetti M24

MicroCoreLabs said:
I needed to tie the READY line high at the 8087 to get the 8086 to execute instructions. Seems that they should've had a pull-up on this signal...
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According to an M24 circuit diagram that I see online, READY is generated by an 8284A chip, and that 8284A asserts/de-asserts READY based on the state of many other motherboard chips. And so one possibility that READY is LOW is faulty circuitry somewhere on the motherboard. A partial diagram is at [here].

MicroCoreLabs said:
I can see lots of bus cycles at the 8086 and the EPROMs, but I dont have anything other than this motherboard so I cant tell if it is executing normally or not.
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Post #32 at [here] indicates that some POST codes are sent to the parallel port. Have a parallel port POST card? That may assist.

MicroCoreLabs said:
Is it supposed to beep at any point in the boot/POST code?
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In post #28 at [here] is, "So part of the POST completes before the display has been initialized, and you only see the codes output via the LPT port. After some components are tested, the display is initialized, the keyboard controller is initialized, and the system beeps. Then the later POST begins, including a full memory test after printing some text onscreen."

Hopefully, someone with good M24 knowledge will comment.
 
I dont own a parallel post card, but maybe i can just check for activity on the lpt port with an oscilloscope. The theory being if the machine is progressing through its POST I would see at least some toggling.
 
MicroCoreLabs said:
I dont own a parallel post card, but maybe i can just check for activity on the lpt port with an oscilloscope. The theory being if the machine is progressing through its POST I would see at least some toggling.
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Or, if you have one, use a parallel printer that has a 'hex' mode; example at [here].

There is an RS-232 serial port on the motherboard as well. Ruud's Diagnostic ROM (RDR) outputs to an RS-232 serial port at base I/O address 3F8h (the standard base address for the first serial port in PC family computers). An example serial output is shown at [here], and by the way, your present situation is described in that in the paragraph that starts with, "If you do not meet ..."
And something that RDR does very early, is to beep the speak in a particular pattern: short-long-short
 
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To follow up, I do see activity at the parallel port outputs so I am satisfied that the CPU is successfully running some of its POST.
 
I am investigating a very similar issue with my recently acquired M24 motherboard. The /AEN1 is constantly high and the CPU/NPU READY is therefore constantly low. Today I powered this motherboard for the first time, and I am also dealing with M24 motherboard for the first time. /AEN1 is ~AEN84 in the Olivetti schematics and controls the wait states to the CPU. That I traced, so far, to ORDY signal being low. Obviously my problem is off motherboard, e.g. either on the videocard, or on the backplane. This differs from MicroCoreLabs's case since they don't have any cards attached to their motherboard and the ORDY is pulled high via R51 on the motherboard.

IMG_6219.JPG

@MicroCoreLabs from your picture it looks the 8041 keyboard controller is missing in the blue DIP40 socket on your motherboard. On the other hand, in the upper left corner of the picture, one can see probably this very CERDIP chip on a white plate, being probably intentionally removed.
 
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Hmmmm, hmm, this awful semi-standard Olivetti design... What do you like about it? Maybe exactly the effort to adapt it to the normal PC world. For now, I liked the Olivetti documentation alone. Anyway, the saved scraps from an M24 are back online. I have connected a Hercules monitor for now, just to see anything at all, later I have a better idea for a monitor. Let's see how to deal with the keyboard which, of course, I don't have. It is odd (to me) I get no keyboard error without a keyboard connected. IMG_6222.JPG
 
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