Re: Troubleshooting the disk drives in a 8296D

From: Nicolas Welte (
Date: 2004-12-05 14:22:11

Hallo Marko,

Marko Mäkelä wrote:
> Interestingly, the FDC ROM is no way close to "fdc-2.7b.bin" from
> a 8296D.  The diffs of the upper 1024 bytes are 130 lines, while
> the diffs above are only 18 lines.  The back plate of this CBM 220

So this machine doesn't have an EPROM installed on an adaptor board, but it 
has only the 6530 installed? In this case, I don't believe the drive can 
work. What is the part number on the 6530?

In any case you have to have the adaptor board with the correct EPROM 
installed. The FDC ROM contains all the drive specific stuff (stepper 
control, all sensors and stuff), so with the wrong version it'll never work. 
In both the SFD1001 and 8250LP/8296D I've never seen a 6530 without adaptor 
board and EPROM. And these are the only drives with the low profile mech.

> Is the FDC ROM responsible for controlling the drive LEDs?  Does the
> main processor control the green/red status LED?

All these LEDs are connected to the 6532 at UAB17, PB3-5 and controlled by 
the main CPU.

> I'll next disassemble the drives one more time to figure out what is going
> on with the write protect sensors.  It's a nuisance to debug this, because
> the drives are normally mounted to the ceiling of the base unit.  Luckily,
> the monitor can be operated next to the computer; the cable is long enough.

Luckily, I have my video adaptor board for these purposes :)


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