Re: 8501 power consumption

From: Rob Clarke <>
Date: Sun, 12 Feb 2012 18:28:03 +0100
Message-ID: <>
The datasheet lists the typical consumption at 125ma. From my experience 
the 7501's do run slightly cooler, but still seem to have a comparable 
failure rate. Like I said previously, Bil had said somewhere (and I 
can't remember where - it might have been on one of my FB postings) that 
he recalled it was a resistor on the mask that should not have been there.

I will try and do the same on a datecode 1490 CSG 8501, which I think 
run much cooler. I find it really surprising that you don't think they 
run hot. The case of the all the 264's except the C16 are very cramped 
and don't allow for much convection. If I lift the case on a +4 or 116 
that has been running for an hour, I cannot keep my finger on the CPU 
for more than a few seconds before it trips my pain threshold. I've 
never tried that on a 6569 but aren't they usually heatsinked by the cage?


On 12/02/2012 18:05, Gerrit Heitsch wrote:
> Hello,
> since everyone says the 8501 CPU has a high failure rate due to 
> overheating, I did some measurements by lifting Pin 5 (Vcc) from the 
> socket and using an Amp meter set to 200mA between it and +5V to see 
> how much power it really needs. The measurements were taken with the 
> system sitting idle at the welcome screen after waiting for about 30 
> secs for the chip to warm up (power consumption goes down).
> The results:
> 7501R1 datecode 2684:    85mA
> 8501R1 datecode 4184:   108mA
> 8501R4 datecode 4986:   109mA
> To compare against a CPU that is not known for a high failure rate:
> 6510   datecode 2784:    96mA
> The surprise was that the 7501 uses about 23mA less than the 8501, I 
> would have expected the opposite.
> In any way, even the 109mA translate to at most 545mW the chip has to 
> dissipate. That's well inside what a 40pin DIP IC can handle, it's 
> nothing that would cause it to overheat, the 6569-VIC in a C64 runs 
> much hotter.
> Unless there is a hotspot on the 8501, overheating can't be the reason 
> for the high failure rate of this CPU. Still, a heatsink will cause 
> the die to run cooler and slow down whatever causes the failure.
>  Gerrit
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Received on 2012-02-12 18:00:22

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