Re: 264 Series and their chips

From: Gerrit Heitsch <>
Date: Thu, 11 Aug 2011 18:32:12 +0200
Message-ID: <>
On 08/10/2011 09:08 PM, Hársfalvi Levente wrote:
> On 2011-08-09 20:40, Gerrit Heitsch wrote:

>> The idea I had was that the die inside the package has more than 40 pads
>> including a full 8 Bit port and all the other signals. So that when
>> bonding the die the machine can be programmed to produce the desired
>> pinout... It would have made production cheaper since you only needed
>> one mask set for all 3 CPUs.
> The problem is - these bits really "don't exist", to the point that you
> can detect their absence from the ports by code. If the die had a full 8
> bit port, you'd need to be able to set/reset the "missing" bits in at
> least the data direction register (and also in the data register, at
> least, if the respective bits were previously defined as outputs),
> regardless to the fact that these port bits were unconnected to the
> package pins. Contrary to that, at least on the 8501 (whose I/O port
> lacks bit5) the missing bit would always read back 0 in both the DDR and
> the data register (regardless of any attempts to set them to 1).

So I noticed when I tried it yesterday evening... Oh well, another 
pretty theory shot to hell...

The reason I came up with this idea was that I read a posting on this 
list where someone stated that the 6510 and the 8500 have the full 8 bit 
port on die and that you could use some clever coding to distinguish 
between a 6510 and an 8500. Go look for the thread called '6510 and 8500 

Looks like Commodore really did make 3 different CPUs instead of one and 
then just using differend bonding options.

> Contacted them, will see what happens (also seem to have a 6529B and
> probably a 8551 for that purpose... who knows...).

The 8551 is just an HMOS version of the 6551(A), so there shouldn't be 
much of a difference. Maybe a tad smaller.

The 6529B is an odd chip, no reset, no PHI2, no DDR... And I've only 
seen it in the 264 series and I've never head about one going bad. 
Replacing it with TTL chips would still need a handful though.

> it's been IMHO a great idea to generate a composite
> video signal on a single NMOS chip, and it'd be nice to see how they
> perfected that from the early VIC-Is from the TEDs and late 856*
> VIC-II-s... )

Even the original VIC did produce S-Video (not called that back then), 
but the VC20 output only gave you composite.

There is one thing I have to do soon, find out why the video output of 
all C16 I have seen so far contains enough chroma signal on the luma 
signal that most monitors will only need the luma signal for a color 
image. Could be the routing of the traces between TED and modulator or 
the modulator itself that's 'leaking' since it's the part that produces 
the composite signal. I have a little cicuit (from a german forum for 
the C64) that allows you to remove the modulator in a C64 and still have 
S-Video output. The picture looks much better but you no longer have 
composite video, only S-Video. This should also work with TED, the 
output drivers on the chip seem to be the same as in the VIC-II. The 
circuit is just a 1N4148,  2 transistors BC547 plus a few resistors and 
2 capacitors.

If there is interest, I could try to convert it to ASCII-Art.


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Received on 2011-08-11 17:00:09

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