Parity vs Non-parity core RAM
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by Bill Degnan - 10/12/2015 17:06 |
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I will have to add (or remove?) the RAM parity jumper to the backplane if I want to use the BA11-K for 11/40's H217C core RAM testing because the backplane is wired expecting a pdp 11/05 S chassis, which uses non-parity RAM (h217D). As I stated earlier it would be nice to be able to test RAM using the BA11-K because I know everything else more or less works.
Currently the no parity RAM set I have installed is not inhibiting correctly address line 2 (or whatever you call light 2). When I deposit into line 2 the data light comes on (i.e. 000 100) but nothing shows when I re-examine. I can load address 000 100 (the light works) and I have tested the front panel (lights work). There are only four cards used by non parity RAM because you don't need the parity card. Of these, the G235 (I think) does the write inhibit to the h217D's core stack. Hopefully the core itself is OK and the issue is with the write being done by the G235 (fix or replace this card). One other thing...It may be that the -15 is too low (?). The -15v is reading as -17.16 off the backplane. The docs say it needs to be within +/-5% (i.e. no more than -16.5v). I understand that the h745 is for +15v and -15v but I don't know which voltage is effected by the one adjustment pot on the h754 regulator. If it's not for the -15v line then I have to disassemble everything and make adjustments to the h765 itself directly. Ug. I read the entire 122 page core RAM manual and read about how the -15V line is used. I would think all lines would be bad and not just one if the -15V was too low and not just one line. So I am leaning to thinking the -17v is not the source of the problem. I am getting good DC LO / AC LO and the CPU is running properly when run the CPU test. Reply |
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