SUMMARY: memory and monitor troubles

From: Derrick J. Brashear (
Date: Fri Mar 19 1993 - 08:58:36 CST

I wrote describing the problems I was having installing a 2nd 4 meg expansion "Carerra" board in my Sun 3/160 and the graphics problems that seemed to come along with it.

I got many responses, most suggesting that I rearrange my boards and take out the jumpers for BG3 and IACK for my SCSI board. I did that, and it was also necessary to adjust the DIP switches on the 9-12 meg board.
John Valdes <> writes:
>If you have no docs, and it's a Sun 4MB memory board (part # 501-1132), set
>switch 5 in DIP switch U3118 and switch 6 on U3119 to ON (the others should be

Indeed, the machine then recognized all 12 megs. But the monitor was still fuzzy when there was a lot of activity on the machine.

andrews@Erin.GOV.AU (Andrew Scarman) writes:
>To check if it's something like the power supply which is quite possible I
>would remove the SCSI board and try just the CPU with the two memory boards.
>I have seen this problem before when the +5 is out.

Indeed, due to some loose connections between my power supply (which is from a
Sun 2, and plenty big) only 4.5 volts were reaching the backplane. After
some adjustments, it works fine.
Thanks all, I have to demo this machine for someone tomorrow:-)

Thanks to: (Dave Smith) (George Nassiopoulos P-353 495-7181) (Bear) (who, BTW, faxed me the correct board order from
                     the FE guide)
andrews@Erin.GOV.AU (Andrew Scarman) (Anthony Worrall) (Steve Winters) (Michael Harris) (Evan L. Marcus [Fusion Services Group])
Mike.Jenkins@NCTS.NAVY.MIL (Mike Jenkins)
Mike Raffety <>
John Valdes <>
Brad.Albom@Eng.Sun.COM (Brad Albom) (Shelley L. Shostak)

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