Luis' Build

[stephen_usher]

Have you done a continuity test between the pins with a multimeter to catch any shorts?

[lrodriguezrullan]

Thanks. I am not sure what the expected values are. I tested from pin 1 to each other pin and got the following:
1 to 2-9: 41
1 to 10: 0.3
1 to 11: 0
1 to 12-18: 44.9
1 to 19: 10.3
1 to 20-27: 41
1 to 28: 44.8
1 to 29: 0
1 to 30: 0.3
1 to 31 and 32: 10.3
1 to 33: 0
1 to 34: 10.3
1 to 35-39: 0
1 to 40: 44.8
1 to 41-44: 44.9
1 to 45 and 46: 0
1 to 47: 45
1 to 48: 0
1 to 49 and 50: 48
1 to 51-57: 41
1 to 58: 0.3
1 to 59-64: 41.2
1 to 65-72: 0
Does that help at all? Thanks.

[stephen_usher]

It's more testing adjacent pins in case there's a solder bridge.

[lrodriguezrullan]

There is continuity between many consecutive pins in the SIMM socket: 3-4, 5-6, 7-8, 9-10, 12-13, 13-14, 14-15, 15-16, 16-17, 18-19, 19-20, 21-22, 23-24, 25-26, 27-28, 28-29, 29-30, 30-31, 31-32, 33-34, 34-35, 40-41, 41-42, 42-43, 43-44, ...

Not sure what is going on.

[exxos]

I think you should look at the H5 schematic and trace back the simm to the MMU. Looks like bit 8 may not be connected back the the MMU.

[lrodriguezrullan]

Thanks for your help. I will take a look at the schematics as you recommended.

[lrodriguezrullan]

I am sorry. I do not understand how to trace back bit 8 from the SIMM to the MMU.

Is it MDATA8 in the SIMM?

I see that DRD8 maps to D8 on the IC18. Is that correct?

However, the MMU only has D0 to D7. How do I trace DRD8 to D0-D7?

Thanks.

[exxos]

Sorry meant CPU not MMU.

MADx lines , check they go back to the MMU (via 33R resistors).

Connection of D8 goes from simm via the buffers as highlighted below.

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2.JPG (327.01 KiB) Viewed 3126 times

[lrodriguezrullan]

Hmm. There is no continuity from pin 31 of the SIMM to pin 63 of the MMU (MAD8).

[exxos]

Later boards go through a jumper...

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