CMD RAMLink manual warning against 1764 power supply

From: Mike Naberezny <>
Date: Wed, 28 Jul 2021 11:19:58 -0700
Message-ID: <>
Hi all,

In the CMD RAMLink manual (4th Edition, First printing, February 1993):

There's a warning on page 23 about data loss when using the RAMLink with a C64 
and a heavy duty power supply.  It specifically calls out Commodore's own 1764 
supply (in the USA, this supply is like the C128 one but with a C64 plug):

"Note: RAMLink was designed to be used on 64 computers with an original 
Commodore supply.  If you have a 64 equipped with a heavy-duty power supply 
(as was issued with the 1764 REU) or some other after-market power supply, you 
may experience data loss problems with the RAMLink.  Since RAMLink provides 
the power for an REU plugged into the RAM Port, use your original 64 power 
supply when possible.  To help cut down on the possibility of data loss when 
using other power supplies, use the recommended power-up and power-down 
sequences with the heavy-duty and other non-original power supply types."

It's understandable that CMD would recommend against using random third party 
supplies.  However, I think it's interesting that CMD specifically warned 
against Commodore's own 1764 supply.

My guess is that it has something to do with the residual output of the supply 
after AC power is lost.  I'm assuming the RAMLink has a circuit to detect 
power loss and disable writes to the RAM, so the RAM can't be corrupted as the 
power goes down.  If the 1764 supply outputs more residual power than the 
original C64 supply after AC power is lost, CMD may have been concerned that 
their RAM-write cut-off may not function as intended.  That is, however, just 
my guess.

What are your thoughts on this warning and why it may exist?


Mike Naberezny (
Received on 2021-07-28 22:00:03

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