Re: 8501 datasheet / information is wanted :)

From: Gerrit Heitsch <>
Date: Sun, 03 Feb 2013 19:50:22 +0100
Message-ID: <>
On 02/03/2013 07:41 PM, Gábor Lénárt wrote:
> Maybe, however I have two of them, so I believe in my luck. I have even
> found an older mail here about the heating problem (a not needed resistor on
> the mask of the CPU or so?), but since I would drive the CPU at a constantly
> 1MHz clock (afaik in C16/Plus4 it is clocked at 1.76MHz during the TED
> video blanking periods), I guess I won't fry it if they managed to survive
> their lifespan in their original place (Commodore 16) ;-)

Add a heatsink.

There are 3 main reasons for a deas 264 system.. CPU, TED and PLA.

> The test circuit has UM6502 currently, so
> some modification is needed, I guess (I even don't know if 8501 needs two
> phase clock or not, etc).

The 8501 needs only PHI0. But, in order for R/_W to  work properly, you 
also need to supply a clock signal to the GATE IN pin. In the C16, they 
use the MUX-signal for that.

> Well, yes, just I thought that maybe 8501 is not stable enough to run
> constantly at 1.7MHz clock.

It is... And if you know how, you can even overclock it to about 2.2 MHz 
by setting TED to NTSC while using a PAL crystal. You won't get a usable 
video output, but the system will run. I did have a heatsink on the 8501 
when I did that though. Also, the 7805 was no longer inside the C16 when 
I did it, so the system was running less hot.

> I am just curious here, this is one reason I would love to see
> the "official" MOS 8501 specification/datasheet.

So am I, but I haven't seen a datasheet for the 8501 anywhere.


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Received on 2013-02-03 19:00:37

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