James,
> Bit 0 maps to column 22 on the memory board, so the suspect chip is the
> one at coordinates E22. (If that isn't it, I think the only other
> possibility is B22.)
You were right on the button here! I piggybacked a 4164 over the IC at E22 and the board passed the memory check with no problems. It seems that's the faulty one allright. Later today I'll extract and resolder a replacement in.
> I think the four possible slot combinations might give different results,
> so try each configuration with the bad board:
> - in MEM 1 with MEM 2 empty
> - in MEM 2 with MEM 1 empty
> - in MEM 2 with a good board in MEM 1
> - in MEM 1 with a good board in MEM 2
In a few minutes I'll run these tests with the second board and post up the results. Stand by..
Terry
>
>>One USED to come
>>up with a parity error. Now it doesn't even get that far. Instread I get
>>a
>>checkerboard pattern so there might be more than one chip faulty on this
>>one.
>
> I think the four possible slot combinations might give different results,
> so try each configuration with the bad board:
> - in MEM 1 with MEM 2 empty
> - in MEM 2 with MEM 1 empty
> - in MEM 2 with a good board in MEM 1
> - in MEM 1 with a good board in MEM 2
>
>
>>The second board comes up with a read/write error. Using just that one
>>board in memory slot one I examined the words at the place indicated and
>>found..
>>
>>00000186 0000 0000 0000 0001 0000 0000 0000 0000
>>
>>Using your rule of thumb, this would seem to be Row E, yes?
>
> Yes, that's correct (I hope).
>
>>translate this to exactly which bit this is and also what column? I do
>>know what binary is and how it (and hex) translates to things regarding
>>8-bit but not really at the chip level . Are you able to elaborate (or
>>point me to a URL) on how this is translated? I assume these words are in
>>hex? I assume so if you can get something like 4000.
>
> Yes, the words are in hex. Each character of the four in one word is one
> hex value, from 0 to F, and those correspond to the 16 possible binary
> values of 4 bits.
>
> The bit positions are (sometimes) numbered, with bit 0 being the least
> significant, and rightmost bit. Your value of 0001 has the rightmost bit
> set, and that is bit 0.
>
> Bit 0 maps to column 22 on the memory board, so the suspect chip is the
> one at coordinates E22. (If that isn't it, I think the only other
> possibility is B22.)
>
> I know that's not a clear explanation of the bit numbers, but perhaps will
> suffice.
>
> If there is just one bit set (ie. only one bad chip), then there are 16
> possible values for the word, which map to memory board columns as
> follows:
>
> Word Bit# = Column
> ---- -- --
> 0001 0 = 22
> 0002 1 = 21
> 0004 2 = 20
> 0008 3 = 19
> 0010 4 = 18
> 0020 5 = 17
> 0040 6 = 16
> 0080 7 = 15
> 0100 8 = 1
> 0200 9 = 2
> 0400 10 = 3
> 0800 11 = 4
> 1000 12 = 5
> 2000 13 = 6
> 4000 14 = 7
> 8000 15 = 8
>
> If there is more than one bad chip, there will be more than one bit set,
> and you'd get a character other than 1,2,4,8, or more than one in the
> word.
>
> Good luck!
>
> James
>
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