C4PMF not working

[dave]

Great!

[dave]

Does anyone know what the 'H' means in the H/D/M? prompt?
/Jeff

It stands for Hard disk.

[Jeff]

Does anyone know what the 'H' means in the H/D/M? prompt?
/Jeff

It stands for Hard disk.

As opposed to "D" for the floppy Disk?

Was there ever a hard disk option?

/Jeff

[dave]

Yes, the C3 series had an option for either a 29MB or a 74 MB hard disk. Those were huge at the time. The "H" option used different boot code from the "D" option, since the hard drives were controlled by a different hardware subsystem from the floppy controller.

[Jeff]

Yes, the C3 series had an option for either a 29MB or a 74 MB hard disk. Those were huge at the time. The "H" option used different boot code from the "D" option, since the hard drives were controlled by a different hardware subsystem from the floppy controller.

Is there any information available on how to hook one up? That would be tremendously cool!

/Jeff

[dave]

Yes, the C3 series had an option for either a 29MB or a 74 MB hard disk. Those were huge at the time. The "H" option used different boot code from the "D" option, since the hard drives were controlled by a different hardware subsystem from the floppy controller.

Is there any information available on how to hook one up? That would be tremendously cool!

/Jeff

I am not sure. As far as I know, the hard disk systems ran on OS65U just like the floppies. Of course, to run native software, you'd need the special 590 and 592 cards, plus a really old hard drive. I think it would be easier to drive an IDE disk using the PIA from the disk interface board, and patch the OS software for IDE access. Of course, you'd have to boot from floppy first, unless the boot ROM were modified as well.

I wonder if there are any functional C3 disk systems out there. . .

Dave

[Jeff]

Well as it turned out, I must have mixed up the old, bad IC with the new good IC. Fortunately, I bought more than I needed, so I grabbed 2 fresh ones, out of desperation and installed them. Now everything seems to work! I have used the Monitor to test all the memory from $1000 through to $BFFF in $1000 increments. All seem to work well. I can even change graphic modes using the $DE00 register.

At various points of my diagnostic, I turned on the machine without certain IC's installed and I witnessed random high-res pixels all over the screen. Unfortunately, I didn't make a note of which ones. Also, I have stored data in the memory that is high-res mapped to the screen and no pixels appear. So I assume that there is a address register or flip flop somewhere that controls the appearance of the high res graphics. I have not completed the schematic yet, but I have mailed it to you so you could look at it. I tried to attach it, but PDF isn't allowed. Perhaps you could tease out the address to twiddle to get the graphics to turn on. Or point me in the direction to further my investigation of the schematic.

/Jeff

[Jeff]

Well, victory was short lived. I decided to let the machine "burn in" for a while, and sure enough a new symptom arose. It seems there is now a video issue. I am not sure where to look, so I was hoping that your trained eye could suggest a direction to investigate. This is what is now on screen:

Screen Shot 2014-05-01 at 1.30.23 PM.jpg (227.12 KiB) Viewed 4552 times

When I press key M, the display changes where the prompt is from "0/0/0?" to "????//??" so the CPU is working, and something seems wonky with the character generator circuitry. Another clue is the "/" characters only appear on the upper half of the screen. Im still adding to the Schematic, and have emailed you the latest.

Regards,
/Jeff

[Jeff]

I have done some further testing.

I used the monitor (rather blind) and stored some values directly into screen memory. At $D444 I stored a $00 and got the racing car, and I also stored a $FF and got the NW facing tank. so I think the $D400 through D7FF video is working fine.

At $D100 I stored a $00 and a large house ($0F) appeared on screen.
Storing $FF displayed the NW facing tank (as expected).
Storing $AA displayed the NW triangle ($AF).
Storing $55 displayed the underscore ($5F).

It seems that the first chunk of video memory is always returning xxxx 1111 or $xF.

Cheers
/Jeff

[Jeff]

I must say, I really do find this forum useful! Even just using it to log my thoughts and steps.... It assists in refining the diagnostic process.

I pulled up the C4P 540 schematic and noticed that the $D000 RAM for ID0-ID3 was U2C. Attached directly to its data lines was an 8T26, so I changed it with a new one. No change.
I then decided to swap the RAM chip with its brother (sister?) the $D400 RAM and see if the problem moved with the RAM. IT DID! Unfortunately I do not have any extra 2114's at the moment, so I decided to swap it with the Color RAM at $E000, since, for now, I am not using colour. I have 16 2114's on order now.

Swapping the RAM with the video RAM solved the issue. My boot screen is back to normal, looking lovely!

Cheers
/Jeff