NetBSD TK70 question (solved)

Christian Corti cc at
Fri Mar 18 04:28:07 CDT 2016

On Thu, 17 Mar 2016, Christian Corti wrote:
> simple read(). All I get is
>  mt0: unknown opcode 0x80 status 0xc01 ignored

Ok, I was fishing deep in the TMSCP protocol manual, and after fiddling 
with the MSCP driver I found out that Opcode 0x80 (OP.END) alone (page 
A-2) means MSCP protocol violation (originating from the TQK70), and 
status 1 with subcode 0 (page B-3) means invalid message length... aha!
I was issuing a read() with a requested length of 65536 bytes, too much, 
maximum is 65535. After I had reduced the length I could read the tape!
So the following is for the records:
1. NetBSD doesn't know how to deal with such an MSCP error
2. SimH (GIT version) improperly ignores invalid buffer lengths


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