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Tom, You can follow the link Jeff supplied but also can just hook up the drive, power it all up and and calibrate to give a 6us pulse from the Q output of the 74121 (pin 1). But a SA850 is a eight inch drive I believe ,you will need to change things on the 610 if this is the case Need to move the tx...

I have not bumped up the system to 2mhz yet , ideally the software should work with a stock system so optimizing the code will be the best approach.

Nor does it have nice serial input and output routines in its SYN600 monitor ROM (At least I am not aware of them!). This is what works for me on the 510 serial system with SYNMON1 65A serial ; OSI MONITOR ROM ROUTINES LOADF = $203 ; LOAD FLAG SAVEF = $205 ; SAVE FLAG INPUT = $FE00 ; GET CHAR FROM ...

I now have 8 inch drives up and running, so I am able to work on the dump software. I ran both versions on my setup and get the same thing, byte missing every 5 or 6 bytes. I checked the memory locations and it is also wrong. Buy looking at the code im thinking the read byte loop is to many cycles t...

So the signal coming from 610 pin 9 going to floppy 22 is fine? it works fine with the 600b but not 600d how are you booting the system to get to A* Do You get proper read with a disk already made? have you probed all control signals coming from the 6821 What type of drives are you using? are you us...

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Double cool !!, I would also like to know your assembler I had to change the syntax for my compilers

Watch those rams with the flimsy pins I had a batch that checked out then started dying they seemed to work but when I ran them in my ram tester they failed

I would recheck your timings on the 610 and separator, also are these 5.25 disks on old drives or did you switches drives from the one you made the disk with
do a memory dump after it hangs