Wanted: SIMH VMS quick test

Chuck Guzis cclist at sydex.com
Tue Dec 16 13:35:18 CST 2014

On 12/16/2014 11:13 AM, Rich Alderson wrote:

> It's a little more complex than that.  Bob was using PDP-11 tape drives as
> his model, and they *do* insert an extra null(?) byte at the end of odd-
> length records.  I think, but have not verified since my KS systems are
> not running right now, that the RH11 on the KS's Unibus may do the same
> thing, but for now that's just a guess.

..and, as a counter-example, there is at least one system/vendor where 
tapes are usually written in multiples of 3 8-bit bytes (ANSI labels 
being the exception).  CDC 6000, for example--6 bit characters and 
12-bit PPU words translate 2 PPU words/4 6-bit characters) to three 
9-track frames, so odd-byte length records are not unusual.

So perhaps the best way to go is not to pad anything.


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