From: ohland@charter.net   
      
   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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