Re: high level on different 6502

From: didier derny <>
Date: Sun, 6 Nov 2016 21:29:55 +0100
Message-ID: <>
tried on the MICRO KIM 1 and 2 REPLICA 1  4v with rockwell 6502 2.8 / 3v 
with synertek
it is clear that there are less components on the bus of these 2 machines

changing the 6502 with a higher high level does not change the 
instability of the replica 1  tenth edition...
these machine are rebuild made by Vince Briel, the micro kim and the 
replica 1 TE are working fine
the replica 1 tenth edition is a nightmare... a finger around the 
propeller reset the 6502 every 2s (about)
never found a solution... I thought that changing the 'high' level could 
solve the problem...
on the replica 1 te   the 5v->3.3v is done with 74ls245 + 1k resistors
on the replica 1 tenth  the 5v -> 3.3v is done with 1k resistors 
directly on the bus

this second replica is about to be reduced to a stack of component + pcb 
for the trash :(

On 06/11/2016 15:13, Gerrit Heitsch wrote:
> 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.
>  Gerrit
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Received on 2016-11-06 21:00:02

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