Re: high level on different 6502

From: Gerrit Heitsch <>
Date: Sun, 6 Nov 2016 15:13:56 +0100
Message-ID: <>
On 11/05/2016 09:37 PM, didier derny wrote:
> while checking some signals on the 6502 of my 8032 motherboard
> I found the 'high' level rather low 2.5v  (I expected around 4v...)
> so I took my SYM1 board and tested several 6502
> MOS         6502       around  4v
> Rockwell  6502       around  4v
> Rockwell  65c02     around  5v
> Synertek  6502       around  2.5v
>                  CM630   around  4v      (bulgarian clone)
> I tried several 6502 of each type...

Since I was curious and able to test it... A few years ago I built 
myself a replica of the EMUF232 on a perfboard (was a real pain in 
the...). That's a 6502 system with 2 x 6522, 1 6551, 32KB RAM running at 
1.8432 MHz. As a CPU I used a SY6502A, datecode 8047.

When checking the address lines on the scope today, the CPU produces a 
HIGH of 3.5-3.7V. So it can't be Synertek in general unless the drivers 
are less powerful than Rockwell and MOS and your board has more load on 
the lines. If possible, check the SY6502 in another board, maybe a 1541.


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Received on 2016-11-06 15:00:02

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