So. Comparing the 9533 system board to a 9556-SLC2, it seems the TI
91F9906 SCSI controller is a close fit.
This seems to have been planned as a Local Bus SCSI implementation, the "Monarch". I further postulate one of the empty solder pad outlines
would have had an N80C32-20 MCU for the SCSI controller.
Louis Ohland wrote:
CR7 probably TERMPWR diode
R34 part of that TERMPWR thing
J7 60 solder pads, most likely a C60
J9 50 solder pads for internal SCSI
OS1 some SCSI related frequency
U20 SCSI controller 164 pin flatpack
U19 44 pin PLCC ?
U33 28 pin TSOP or whatever, probably memory
What do we got for frequencies [Kenneth]
OS1 unpopulated
OS2 unpopulated
OS3 48.0000 floppy
OS4 50.0000 CPU
Y1 4.0 MHz
Y2 14.3 MHz system
Y3 32.8k RTC-ish?
https://www.ardent-tool.com/9556/
9556 [SLC2] oscillators
OS1 40.0000 MHz osc
OS2 22.1184 MHz osc (UART)
OS3 14.3181 MHz osc (adapters)
OS4 50.0000 MHz osc (CPU)
OS5 24.0000 MHz osc (FDC)
Y1 32.768 KHz xtal (RTC)
Y2 4.0 MHz xtal (XGA-2)
So... OS2 22.1184 MHz? OS1 40.0000 MHz?
OBTW, if you peek at the solder side of the 9533 system board, you
will see four rows of inductors under J7, L13-L17, L21-L25, L32-L35,
L38-L41 for a total of 18 of these inductors or L-C or dilithium xtals...
Again, if there's nothing connected, why populate them?
Louis Ohland wrote:
https://www.ardent-tool.com/9533/Planar_Photo_Front.jpg
Why populate an unused component if there's nothing there?
The RN between J7 and J9 solder pads does WHAT in the absence of a
SCSI controller?
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