MOUNTing Problem

Discuss construction, troubleshooting, and operation of the Altair 8800c computer

MOUNTing Problem

Postby toml_12953 » May 30th, 2019, 9:03 am

In my 8800c, I'm using the FDC+ with two Teac 55-GFR-149 5.25" HD floppy drives configured as 8" drives. When I do a MOUNT 1, I get an I/O error. If I do an UNLOAD then MOUNT 1 again, it always works. The second try always works.

Any idea what's going on?

Tom L
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Re: MOUNTing Problem

Postby AltairClone » May 30th, 2019, 9:56 pm

I assume you’ve specified two drives during the BASIC startup sequence? What happens if after booting you type MOUNT with no parameters? That should mount drive 1 and then drive 0. Let me know what happens.

Mike
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Re: MOUNTing Problem

Postby toml_12953 » May 31st, 2019, 3:11 am

AltairClone wrote:I assume you’ve specified two drives during the BASIC startup sequence? What happens if after booting you type MOUNT with no parameters? That should mount drive 1 and then drive 0. Let me know what happens.

Mike


Yes, I specified two drives at startup (HIGHEST DISK NUMBER? 1) The first time I mount with no parameters it tries to mount drive 1 first and gets the I/O error. If I unload and mount again, both drives mount OK with drive 1 mounting first.

Tom L
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Re: MOUNTing Problem

Postby AltairClone » May 31st, 2019, 9:14 am

Let me know which disk images you're using on drive 0 and drive 1 and I'll see if I can duplicate your symptoms.

Mike
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Re: MOUNTing Problem

Postby toml_12953 » May 31st, 2019, 9:49 am

AltairClone wrote:Let me know which disk images you're using on drive 0 and drive 1 and I'll see if I can duplicate your symptoms.

Mike


They're "Disk Basic v300-5-F.dsk" in drive 0 and "Games on 300-5-F.dsk" in drive 1

both from your downloads area

http://www.altairclone.com/downloads/ba ... py%20Disk/

I copied them to the floppies with your PC2FLOP program. I'll try to copy them again to see if that helps.

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Re: MOUNTing Problem

Postby AltairClone » May 31st, 2019, 3:15 pm

What if you do "MOUNT 0" followed by "MOUNT 1" immediately after booting - does either mount fail?

Mike
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Re: MOUNTing Problem

Postby toml_12953 » May 31st, 2019, 8:22 pm

AltairClone wrote:What if you do "MOUNT 0" followed by "MOUNT 1" immediately after booting - does either mount fail?

Mike


When I first turn on computer:
MOUNT with no parameter hangs the computer. No OK prompt. If I hit reset then try to MOUNT again, I get DISK ALREADY MOUNTED
MOUNT 0 followed by MOUNT 1 gives DISK I/O ERROR when I do drive 1

After I do the first UNLOAD:
MOUNT with no parameters mounts drive 1 then drive 0 with no error
MOUNT 1 mounts drive 1 with no error

Tom L
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Re: MOUNTing Problem

Postby toml_12953 » June 3rd, 2019, 7:48 am

I thought there might be a problem in the MOUNT command itself since I got garbage when I tried it on my AltairDuino but it turns out it's the MAX3232 that's flaky.
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Re: MOUNTing Problem

Postby AltairClone » June 3rd, 2019, 1:16 pm

Swap the drive jumpers on the two drives so that drive 0 becomes drive 1 and vice-versa. Let me know if the problem changes.

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Re: MOUNTing Problem

Postby toml_12953 » June 3rd, 2019, 7:27 pm

AltairClone wrote:Swap the drive jumpers on the two drives so that drive 0 becomes drive 1 and vice-versa. Let me know if the problem changes.

Mike


Baffling! I switched the drive jumpers but kept the drives on the same drive cable connectors. MOUNT now works in all cases!
I don't see a removable resistor pack on the drives. Is there one? If so, where?

If one drive had the resistors but the other didn't and I didn't have the drive with the resistors on the
last cable position would that explain the problems I was seeing?

*UPDATE* I switched the drives on the cable so that the new drive 0 is where the old drive 0 was and MOUNT still works fine in all cases.
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