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Re: MiniFP users - check this

I have the following jumpers on my FP Mini:

MWRT -shorted
PROT - open
UNPROT ON -shorted

These are the jumpers along the bottom of the board.

With this configuration I am not able to use the Deposit toggle switch to change the contents of RAM.

However just for fun I changed the UNPROT jumpers so that UNPROT ON is open and UNPROT OFF is shorted. With this configuration I was able to use the Deposit toggle switch to change RAM memory. Now I am using Josh's 8080 board so when I reset the first 32K is ROM, so I needed to set memory above that to check the Deposit function.

Anyway if any of you want to try this setting let me know what happens.

On Friday, April 24, 2015 at 8:13:16 PM UTC-4, AltairManRich wrote:
All —

Not sure if this may be related to the problems we’re seeing with this board, but I was looking at my CompuPro backplane and I noticed that pins 20 and 70 are grounded per the IEEE696 specification, while on the IMSAI, only pin 70 is grounded. Pin 20, I believe, is the UNPROT signal.

Maybe it’s not the problem, but I think everyone should try isolating pin 20 from the bus by leaving both J3 and J4 open or otherwise confirming that pin 20 is not connected to ground at the bus. The only issue with this is if you use an early memory card that requires a high on pin 20 to enable writing it won’t work. I remember having to isolate 20/70 on certain CompuPro cards in order to get them to work with the IMSAI. 

Just a thought…


Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator