[vcf-midatlantic] Zilog System 8000

[Jonathan Gevaryahu]

On 11/17/2015 2:18 PM, Dave McGuire via vcf-midatlantic wrote:
> On 11/17/2015 12:38 PM, Oliver Lehmann via vcf-midatlantic wrote:
>>> Keep in mind: it's the metal drive roller which determines tape
>>> speed, not the roller.
>> This is exactly why I know as well. It is just there to get the "speed
>> on the tape" but it is not mission critical to get the dimensions 100%
>> correct.
>> Remember - the capstan dimensions change over time anyway because the
>> material will be constantly removed during operating the tape. This is
>> a normal process. IF the capstan dimensions would be vital for the
>> correct function of the tape drive, it would have been unable to read
>> the times not far after it was shipped - probably.
>    Actual tape speed over the head is actually not that critical for many
> types of tape drives.  Most modulation/encoding schemes are
> self-clocking, either through separate clock tracks (DEC TU56) or
> embedded clocks that are recovered via a phase-locked loop.  Getting
> close will do it.
>
>    Speed variations, on the other hand, can be bad if a PLL is used for
> clock recovery.  If the period of the speed variation falls outside of
> the clock recovery PLL's loop bandwidth, the loop could lose lock,
> resulting in the loss of the clock.  So, keep those replacement rollers
> as round as possible, but don't worry so much about the exact diameter,
> unless you know for a fact that there is an absolute tape speed
> requirement, which is rare.
>
>                  -Dave
>
These z8000 tapes are MFM, so they should be self-clocking, I think?

-- 
Jonathan Gevaryahu
jgevaryahu at gmail.com
jgevaryahu at hotmail.com