Why doesn't this jumper relocation work?

[superben51]

Those are some dirty controller ports.

Was just thinking that.

 

[Ashen]

You gave up and wired every trace. I know that feel. You really shouldn't have to, all the ground lines are tied together on the back of the motherboard.

You would think that would be the case. But after I took those pics I started disconnecting the ground wires one by one and testing after every disconnect. Low and IGNORE, second ground pin I disconnected the system would no longer boot (pin 6). Sane thing occured as I proceeded down the line of "ground" pins.

Now the only explanation I can think of here is that the pins we think are ground on the MB itself are in fact not ground, but very low resistance connections to something or other that go to the ram chips and must be connected to ground by the jumper pack to make the system boot properly.

I may be wrong, but its the only explanation I have for now based on the limited testing I've done.

 

[βeta]

Jumper paks are stupid.

 

[ttsgeb]

... Do you think that pming kibble on benheck this annoying bit of info might get him back started on those crazy PCBs he was working on?... Because that would be pretty sweet to see finished... Even if it doesn't really change much now.

 

[βeta]

I talked to him about something along these lines months ago. He's pretty gone.

 

[ttsgeb]

So... in reading through the IMA BUILD A N64 PCB threads on BenHeck, I actually found some potentially useful info on this.

http://forums.benheck.com/viewtopic.php ... 05#p324205

From what I understand of that, wire placement matters as much as wire length. If you relocate it any considerable difference from stock, you probably need to replace the resistors with something of a different value.

I know you were both reading that thread when it was happening and all, but it's entirely possible you didn't actually know what it said, or simply forgot about it.

Sorry for the bump or something?

 

[βeta]

I did totally forget about that. I have no idea how to figure out new resistor values, other than experimentation.

 

[ttsgeb]

Assuming the expansion pack has terminating resistors as well, I would test those and compare resistor values and trace lengths between revisions. From there, I would use that information yo make an educated guess at change in resistance per trace length and use this metric to approximate what you would need the resistor value to become.

Still assuming that the expansion packs have terminating resistors, and looking at your first attempt, I would try using that resistor pack instead of those from the jumper pack.

But then again, I don't really know that much about n64s, and don't have the parts to play with. Just more of that speculation thing I do.