RK8E Plessey Clone and Data Break Error

Marco Rauhut marco at familie-rauhut.eu
Tue Oct 18 14:55:54 CDT 2016

Hello all together,

i restore a rk05 disk drive in combination with an Plessey RK8E clone 
Now the drive itself is restored, and the connection cables are built.

My problem is that the rk8e diskless controll test (dhrka) fails with an 
data break error. The diskless controlltest
is running throug all register and also the databuffer test. But in the 
first data break routine it fails.

Then i toggled in the Example program from the maintanence vol.III, 
Single Cycle Data Break Transfers (Write than Read).
With this program the content of the SwitchRegister is written through 
the data buffer registers and read back to the memory.
Afterwards it is compared to the original SR content. I found out that 
the routine is running if SR=7777. Deeper investigation results that the 
bits 0, 1, 4, 6 and 9 have to be one`s to run the routine. The other SR  
bits are switchable while running the program.

Next thing i did is trying read data with futil. i could read data form 
the disk. But with many read errors.
Because i do not know anything about the allignment between my diskpack 
and the drive, i formated the pack
with the RK8E Formater (dhrkd). The write part of the format is running. 
In the disk checking part the formater fails.

Anyway. Then i used futil and scanned the whole surface off the 
diskpack. On the whole disk are 5 bad blocks left.

Now i am able to dump blocks from the disk. But it seems that no matter 
witch block i dump out, it is the same block
all over the disk. Afterwards i tried to modifie some words in block 0. 
And this is working. When i write the modified block i see the
modification also in every other block of the disk.

Have anyone the lightning idea?

On a Google search i found a post of Rick Bensene from 2014 on this list 
witch described a similiar problem.
In this discussion where talked about an spike in the load signal of the 
current address register.
I checked that and see that this was not my problem.

Thanks in advance

Marco Rauhut

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