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JGRAHAM2

32K RAM EXPANSION

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I built a REV4 version of this expansion. It has a jumper, TI/Ext, to set for internal or external power. The board works great, but doesn’t seem to care how this jumper is set or if it even has a jumper. I want to install a TIPI and I need to use external power to do so. Question: is it normal for it to work with the jumper set in any position? Looks like setting to Ext connects 5V to pin one of the header the TIPI will connect to, so the external supply is definitely needed.

Thanks

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If it is set to internal, then it takes the 5v from the side port of the 4A. 

 

If it set to ext and you do not plug a power source in, it may seem to work, but this is just because enough current is leaked through the address lines into the static ram (and other) chip. 

 

The rev2 version, I actually forgot to route the trace for power and things passed my memory test most of the time, but lots of software failed..  

 

Seems to work != Actually works. 

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I am able to run games that require the extra memory when it is set to Ext and no power attached. I went ahead and setup the TIPI using the external power and all works well. Thanks for your help! (And for your work on these enhancements!)

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23 minutes ago, JGRAHAM2 said:

I am able to run games that require the extra memory when it is set to Ext and no power attached. I went ahead and setup the TIPI using the external power and all works well. Thanks for your help! (And for your work on these enhancements!)

 

Some poor soul in the future is going to read that it 'works' and then lose a days XB programming because they followed this misinformation. 

 

This is extremely dependent on out of spec behavior of the chips and a bunch of luck. 

 

I'm glad that you have chosen to power it.

 

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29 minutes ago, jedimatt42 said:

 

 

Some poor soul in the future is going to read that it 'works' and then lose a days XB programming because they followed this misinformation. 

 

This is extremely dependent on out of spec behavior of the chips and a bunch of luck. 

 

I'm glad that you have chosen to power it.

 

I’m just reporting the behavior as it concerned me that connecting the external power could damage something since the memory expansion functions when the 32K is set to external. I have built 3 of these and they all function this way. The TIPI, I’m sure would not work, but I didn’t try that. If this post could be seen as “misinformation”, then I would be happy to delete it. (If that is possible)

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Sorry, I didn't mean to call it 'misinformation', I meant to say 'misleading information'. This was a 'whole thing' when I first released it. 

 

Other fun things are that the LED control input floats when the 4A isn't on. So with external power, you can influence it with your fingers... 

 

 

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16 minutes ago, jedimatt42 said:

Other fun things are that the LED control input floats when the 4A isn't on. So with external power, you can influence it with your fingers...

I have seen this.  On my 32k units (which are the original release) when external power is selected but not applied, the LED illuminates dimly, same as on the CF7+/nanePEB.

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19 minutes ago, jedimatt42 said:

Sorry, I didn't mean to call it 'misinformation', I meant to say 'misleading information'. This was a 'whole thing' when I first released it. 

 

Other fun things are that the LED control input floats when the 4A isn't on. So with external power, you can influence it with your fingers... 

 

 

I appreciate you designing and releasing it for us to build and use. It is an awesome upgrade to make these old computers more useful and should encourage more development.

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