Re: Xebec Card Help

[Patrick Schäfer <Patrick.Schaefer@topmail.de>]

"Brian A. Davis" schrieb:

> Can someone explain to me exactly what removing pin 25 is supposed to do?
> I would also like to know what types of hard drives (SASI/SCSI) can be
> attached to this card.

One side of the SCSI connector carries all the data signals, and a +5V
supply for standalone termination resistors. The other 25 lines are
ground connections, so that every second line in the cable is grounded. 

If you plug in a SCSI connector the wrong way, you will short the +5V
supply. An Apple power supply is rather weak, it would not turn on
anyway (it just makes a clicking sound). However, a PC supply is strong
enough to burn your SCSI cable. To avoid this, the ground pin opposite
to the TermPower +5V pin is missing.


 
> On another item with this Xebec card, there looks to have been a
> modification to this card. I believe that there is a different ROM chip
> installed from what was originally used.