Re: Drive disconnect switch for SX 64

From: Ingo Korb <>
Date: Tue, 30 Nov 2010 23:56:34 +0100
Message-ID: <>
Nate Lawson <> writes:

> Jim's analysis is good. I've found that with one drive that is off but
> connected to the IEC bus, it doesn't drag the idle level too low (3.3v
> high versus 5v).

Unfortunately that depends a lot on the drive. I've seen a high level of
just 1.5V on the bus with a C64, a 1541-II (off) and an sd2iec-device
(with 4k7 pullups). I assume that the manufacturer(s) of the bus-driving
74xx chips in the disabled drive is just one of the factors that
determine how high you can get the voltage in this case.


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Received on 2010-11-30 23:00:17

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