Re: 264 Series and their chips

On Aug 11, 2011, at 3:10 PM, Hársfalvi Levente wrote:

> On 2011-08-11 18:32, Gerrit Heitsch wrote:
>> 
>> 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
>> differences'.
> 
> Ah, Nicolas Welte's findings about the unimplemented portbits of the
> 6510/8500 (...one kind of stuff I like cbm-hackers for :-) ).
> 
> Thinking it over, even that one seem to contradict with the idea of a
> full 8-bit port that was supposed to be implemented on the 6510/8500's
> die. Bits of the output register don't fade out by the corresponding I/O
> pins absence. That might rather suggest that MOS already had a 8-bit
> port equipped CPU design, maybe more than one CPU design with several
> features incorporated into the 6510 at the time they actually needed the
> 6510, and pasted/stripped parts as needed, with no care for leftovers
> (ie. those that didn't hurt them).
> 
> It's interesting though, that they didn't change the design once they
> switched to HMOS-II. I thought that move needed a more or less complete
> redesign of the chip. Still, the artifact has been kept (it's only the
> manufacturing process that results in different time until the fadeout
> happens), which suggest they didn't change the layout. ...I'm really
> looking forward for this thing to be demistified.

In "On the Edge", one of the C64 engineers said they made the 6502 into a core before creating lots of variants, such as the 6510. (I believe it was Winterble, but not sure.) Anyway, since the 6502 was hand-drawn, I assume what they did was reconstruct the gate design in more modern CAD tools to allow it to be modified more easily. This also would allow them to change processes, do design shrinks, etc.

HMOS is still an NMOS process, just with higher density. Most of the early Amiga chips were HMOS too. I think it wasn't until Commodore started outsourcing some of the chip production that they moved to CMOS.

-Nate


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