RamFAST/SCSI and Archive Viper 150

[jdb8042@tam2000.tamu.edu (John Donald Baker)]

After some more fooling around with the Viper, I think I've hit on a
possible explanation why it was not behaving rationally.

As I received it, the drive was not supplying terminator power.  Although
my RamFAST is supplying terminator power, it's possible that it's just
not enough to supply an entire SCSI chain with it.  Thus, it's possible
that there were undefined logic states on the bus by the time the signals
made it out to the Viper.

The lack of TERMPWR supplied by the drive was evidenced when I plugged the
drive (with pass-through terminator) into my Amiga.  This promptly brought
the Amiga's power supply to it's knees since it had to feed TWO terminators
(one on each end of the SCSI bus) and could no longer make +5V due to the
current demand.

I finally discovered the mystical JP12 on the Viper drive which, when jumpered,
supplies termination power on the part of the drive.  In this configuration,
my Amiga liked the terminator.

It'll be two weeks or so before I can test the Viper with my RamFAST and //e
again.  Now with extra juice out there on the bus, things could be different.

(Hooked up to the Amiga, I can write and read small amounts of data on
the drive.  however, I can't stream data and eventually the SCSI bus
locks up and hangs the Amiga or it looks like the Amiga runs out of memory
(although I have 5MB in it).  Strange.

Sorry for the Amiga content in the Apple ][ forum, but I'm testing all the
angles I can think of with the Viper drive.


Feedback appreciated.



John D. Baker ->A TransWarp'802'd Apple //e CardZ180 Z-System nut //
Internet:  jdb8042@tam2000.tamu.edu, @blkbox.com, jdbaker@taronga.com
BBSs:  JOHN BAKER on PIC of the Mid-Town [(713) 961-5817] 1:106/31,
The Vector Board [(716) 544-1863], Z-Node #45 [(713) 937-8886]

http://tam2000.tamu.edu/~jdb8042/