Re: [stella] Supercharger and the 7800?

Subject: Re: [stella] Supercharger and the 7800?
From: Glenn Saunders <cybpunks@xxxxxxxxxxxx>
Date: Sun, 26 Nov 2000 21:52:54 -0800
At 03:45 PM 11/26/2000 -0500, Questerre@xxxxxxx wrote:
Hi, I thought I may have come up with why the Supercharger wont work on the
7800. Could it be possible the chip Protocol does not support the
Supercharger or does not accept the Schargers memory configuration or type.
This may explain why programs will not load - possible memory or CPU
conflicts.  Quest

The 7800 doesn't use a standard 6507, it uses a 6502C which has some kind of dual crystal to clock at either 1.79 or 1.19 mhz depending on whether it's in 7800 or 2600 mode. That might be part of it.

Also, the 2600 does not expose the clock wires or the read/write line to the cartridge port. According to David Crane, some cartridges exploit "phantom signals" bouncing around the 2600 to resynthesize some of this stuff. I think Pitfall II does some of this. I'm not sure if the Supercharger does this, but I wouldn't be surprised.

These "phantom signals" are the kinds of things that Warner Atari would have been smart enough to maintain in the early 7800. Knowledge of the subtleties of the electronics signals inside the 2600s was very complete during the Warner era. Warner Atari engineers had done meticulous studies of these kinds of things on oscilliscopes. I have some of these documents from Jerry Jessop that attest to the level of detail of these studies.

The Tramiel-era engineers wouldn't either know about or care about such subtleties. If they could trim the cost of the unit by a few pennies by removing a few resistors that might have altered the electronic characteristics slightly, which at casual glance didn't hurt compatibility, that was probably good enough for them.

So I think if you put the offending 7800 on a rigorous test bed similar to what the Warner Atari guys used to use, it would probably be possible to track down the critical difference.

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