Subject: Re: Slightly Off-Topic...
To: Kevin P. Neal <>
From: Michael Kukat <>
List: port-alpha
Date: 06/26/2001 06:39:22
Hi !

On Mon, 25 Jun 2001, Kevin P. Neal wrote:
> Uh, to nit pick, the C64 had a 6510 chip, not a 6502. The 6510 had a onboard
> 8-bit I/O bus that showed up at 0x0000 and 0x0001. Each bit in 0x0000
> controlled which direction that line would go. Reads and writes went to
> 0x0001. The C64 wired it up for memory management. I don't remember what
> the C16 did, that was a much much later box. I never quite figured out
> what the point of the C16 was.

I know. But talking about the CPU, the 6510 is exactly the same as the 6502.
There were many derivates of the 6502 with more/less bus signals and
features. Just thinking of the 6504, a 28pin-version with 12Bit bus i think.
Atari 2600 used such a thing. The C16 hat the 8510 or so, which also was an
extended version of the 6502, includes some more I/O bits (6510 had 5 bits i
think) for control purposes, and runs at 2 MHz.

> the memory. Except the "color memory" was 4 bits wide and appeared in
> memory way up high (0xd000 or thereabouts?).

Yes. 0xd800 was it i think. 0xd000 was a mirror of the SID, which officially
resides at 0x4000. I think, but i don't know for sure after several years.
But 4 bits were enough for 16 colors. The nice thing was that feature do
disable all I/O (through that CPU I/O at 0x01) and get access to the full
64KB of RAM.

> Awesome. The very basic concepts of modern computing all in flashing
> colors and moving pixels on a TV screen. Incredible.

This might be the modern version of those computers with all those thousands
LEDs and lamps you always see in old sci-fi movies :)


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