Re: is there any easy way to upgrade a C116 to 64k

From: Gerrit Heitsch <>
Date: Thu, 02 May 2013 18:04:26 +0200
Message-ID: <>
On 05/02/2013 03:28 AM, Bil Herd wrote:
>> MOS did make a 8501R4 in 1986 and there are even 8501 with a 1990
> datecode. Those are rumored to last a lot longer.
> Part of what the process engineers did at MOS was make a chip better by
> studying temperatures and "schmoo plots",  and either fixing things in the
> recipe themselves (or feeding back to the chip layout guys to change
> source and not just paint the masks).

Well, there must have been some changes between the 8501R1 and the R4...

> ->Replace 7805 with switching regulator (RECOM 5V/1.5A type)
> Didn't exist at the time as affordable or the Tokyo office would probably
> have put it in.

They are still expensive (around 10 Euros for the 1.5A version) and back 
then completly impossible, but times change and people want to be able 
to run the old systems as long as possible.

I like the C16 since it has the BASIC and simple Assembler in the 
Monitor that the C64 should have had from the beginning. TED also has a 
few features VIC doesn't (hardware cursor, hardware reverse, full 64K 
access, colors, programmable counters for horizontal and vertical position).

>  For $49 they were
> only meant to last a year or two.

And many of them are still running. Looks like MOS did too good a job.

 From what I heard the ZX guys have the problem and the ULAs are 
starting to go bad, no matter what you do and are working on a wholesale 

> - Add heatsinks to CPU, TED and PLA
> Again product life wasn't never a consideration that I found

Yes... back then, but to keep them running now, getting as much heat off 
the die is a good thing.

>> That makes the system run a lot cooler in general, also meaning cooler
>> dies for TED and CPU and hopefully some more years.
> I am serious when I say that it's hard to believe that ANY system are
> running 30 years later, our typical accumulated MTBF for a consumer system
> was around 2-3 years... that is the ones that weren't already broken
> before we shipped them.  We would gladly sell you a second system if your
> firsts system died.

I'm also surprised how they hold up. But there are also some chips that 
seem to die easier than others. Very stable are the 6510/8500, ROMs and 
VIC in the C64, hardly ever see them fail. Especially VIC runs quite hot 
but doesn't seem to care. Then there are the PLA, SID and 8501 and 8360. :(

It's also interesting what people are able to do with the hardware now 
that it's fully understood. Imagine you'd have been able to play one of 
the newer C64 or +4 demos back when they were unveiled.

> CBM did realize they needed to get into CMOS and had broken ground on the
> new line when I left.  I was told they never finished .

MOS did some CMOS chips, the ones I know are:

5710   found in C128DCR, simplified CIA
5717   Mouse 1351
5718   Gate Array on bridge boards (A2088/...)
5719   GARY (Amiga 500/2000B)
5721   BUSTER (Amiga 2000B)

I don't know if MOS made them or had them made and just stamped their 
number on the package.

> Another example of how the production release was its own animal: There
> was a last minute chance to fix the serial bus, Bob Russell had come up
> with the software fix for the problematic shift register hardware and had
> had the PCB films changed to wire the serial lines to a working hardware
> pin in addition to the software driven pin, the idea was they could at
> least cut over at some point very soon.  Tokyo looked at the film and
> painted out the second connection assuming it was an error and the
> software serial bus became permanent.

I read about that... A simple phonecall 'there seems to be an error' 
would have been enough. Hard to imagine nowadays, but things were 
different back then.


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Received on 2013-05-02 17:00:03

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