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Re: s390 hardware config



When using a real CTC, that is a wire cable between two separate computers, (I haven't seen one of those in years either but they do really exist) it is necessary to reverse the order on one. One machine read=0A00 write=0A01 the other read=0A01 write=0A00. One machine has to read what the other is writing. I learned this in 1968 when I plugged the tape drive cable from one CDC G-15 into another CDC G-15 instead of a tape drive. If I issued a write tape from one machine and a read tape on the other it would copy a buffer of data from one machines memory into the other.

Ivan Warren wrote:
Adam Thornton wrote:

I'm going to be devil's advocate here:

*I* always use the even address as the bottom one of the pair.

Is there anything mandating that that has to be the case?

Adam


Oh.. You're lacking imagination ! You could push that one just a tad further !

1) Use non consecutive pairs (Read=0a00, Write=0a10)
2) Reverse the order (Read=0a01, Write=0a00)
3) Set the pair on different channels (Read=0a00, Write=0b00)
4) Set the pair on different LCSS (Read=0:0a00, Write=1:0a00)
5) What you said : start with even (Read=0a01, Write=0a02)
6) Really wicked ! All of the above ! (Read=1:0b11, Write = 0:0a00)

But eventually, to make it work in a hot plug environment, you're going to have to set some rules if you want the hotplug system to figure out the relationship on its own (A: I'm doing something weird and it doesn't work.. B: Don't do something weird) !

--Ivan



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