Date   : Sat, 09 Mar 2002 13:30:09 -0000
From   : "Richard Gellman" <r.gellman@...>
Subject: Re: WD 1770

>The A3000 & Master Compact both have 1772s in them, not 1770s. The only
>substantial difference is the step rate, which in the 1772 is optimised for
>3.5" drives, so you might have some problems if you try to connect a 5.25"
>drive through a 1772 (unreliabilty problems- it would probably still work).
I
>would also have thought that the DFS/ADFS software needs tweaking for use
>with a 1772.

Yes, the 1772 is idendtical except for half the step rates.
The 1770 provides 6,12,20, and 30ms step rates,
The 1772 provides 6,12,2, and 3ms step rates.
Now on my master 128, I've always had to use *CONFIGURE FDRIVE 3 with every
disc drives I've owned, which is the equivalent of setting the drive step
rate
links on the Model B keyboard. This value is also translated into the bottom
2 bits of any 177x seek command.

If you *have* to use a 1772, I'd suggest you use the highest step rate there
is, i.e. 12ms, this should provide best reliability (dont quote me though).
This is *CONFIGURE FDRIVE 1 on a BBC Master 128, or setting the step rate
links to read binary "0 1" on a Model B.

-- Richard Gellman

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