Re: DRAM refresh

From: David Wood <>
Date: Thu, 13 Oct 2016 22:35:54 -0400
Message-ID: <>
The REU was involved at some point, or so I thought.  The REU was
disconnected from /BA and the  set to read a large block of data from the
c-64, thus getting not only c64 data but seeing data fetched by the
VIC-II.  I don't remember where I read this so we can say <citation
needed>.  It makes sense, and can even be used to scan address bits if a
multiplexer is attached between the REU and the c64 to swap address/data
bytes during DMA transfers.

On a less technical note Ive seen some conceptual research that involved
driving the luminance output partially via a logic probe to see at what
points on a rasterline (or within a frame) lines toggle.  I get that effect
with my hyper-sensitive VGA up-converter- the c64c shows the system clock
pretty clearly as vertical bands, and less so the ras and cas drive.
Badlines aren't too hard to spot if you look for them too.


On Thu, Oct 13, 2016 at 8:23 PM, Jim Brain <> wrote:

> On 10/13/2016 12:45 AM, Marko Mäkelä wrote:
>> On Wed, Oct 12, 2016 at 10:49:09PM +0100, smf wrote:
>> By the way, VICE should correctly emulate the memory accesses of the
>> VIC-II, because it is capable of running the "dadb" test program that I
>> wrote over 20 years ago.
> I've always wondered:
> 20 years ago, what transpired to get you from:
> "Hey, I wonder..."
> to
> "OK, here's how we'll figure out how the VIC works, without anything but
> the C64, an assembler, and the TV screen."
> I mean, I read the articles back in the day, but I never could connect the
> dots on how one figures out how to use software only to uncover the details.
> Jim
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Received on 2016-10-14 03:00:29

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