Re: 264/TED/Plus4 Story

From: Gerrit Heitsch <>
Date: Thu, 25 Aug 2011 18:31:18 +0200
Message-ID: <>
On 08/25/2011 02:03 AM, Nate Lawson wrote:
> On Aug 24, 2011, at 4:54 PM, Jim Brain wrote:
>> On 8/24/2011 12:05 PM, Gerrit Heitsch wrote:
>>> On 08/20/2011 06:21 PM, Bil Herd wrote:
>>>> So there was ONE RULE when I got the Ted project, it has to have xxx number
>>>> of chips (I think it was nine chip) and no more, signed Jack Tramiel. Well
>>>> the TED’s reset circuit consisted of an RC circuit and a 7407. I proved it
>>>> wouldn’t work but I didn’t think about what this really meant as to who had
>>>> designed the computer (the answer was no-one had designed the computer at
>>>> that point) It was an easy argument to make that the computer would fail en
>>>> masse, we HAD to add a chip for reset, didn’t matter which chip, we simply
>>>> could not do it with a transistor or a 7407 gate. (yes I tried feedback to
>>>> create hysteresis  ) The answer came back from the mountain that it was
>>>> okay to add a chip. I remember that people were stunned that I had
>>>> challenged this (some thought I would be fired) and won.
>>> That was the famous 555 timer chip if I read the circuit diagram right. Same way as the Reset was generated in the C64 on the older revisions.
>>> Thanks to whoever added the reset button to the 264. It always irked me that the C64 didn't have one.
>> If everyone else knows, can someone relate just WHY the original 7407 and RC would not work?
> My guess is that the edge wasn't sharp enough. Perhaps a Schottky part would have worked better.

A 74LS14 would have been the better idea but again meant one more chip. 
In fact they used the 74LS14 instead of the 555 on the 250469 boards 
(The ones with the large 64pin PLA) for the C64 to generate the reset 


       Message was sent through the cbm-hackers mailing list
Received on 2011-08-25 17:00:38

Archive generated by hypermail 2.2.0.