Re: cbm 8032 motherboard + 4164

From: Gerrit Heitsch <>
Date: Wed, 12 Oct 2016 16:24:19 +0200
Message-ID: <>
On 10/12/2016 07:34 AM, Marko Mäkelä wrote:
> Hi Ruud,
> On Wed, Oct 12, 2016 at 05:15:44AM +0000, Baltissen, GJPAA (Ruud) wrote:
>> Hallo Gerrit,
>>> 41256 need 8Bit refresh...
>> Nope. Otherwise the Finnish's and the 64'er's 256 KB hack on the C64
>> wouldn't
>> have worked.
> The VIC-II in the C64 (as well as the VIC-IIe in the C128) implements an
> 8-bit refresh counter. That was proven in 1994 by the test program that
> Andreas Boose wrote, to check which memory addresses the VIC-II chip is
> reading.

There was no need to prove that... VIC (and TED) _has_ to supply an 8Bit 
refresh since the 64Kx4 DRAMs and some of the 4164 need it. If VIC was 
only doing 7Bit, Commodore would have been limited with the 4164 they 
could use and the 250466 and 250469 boards couldn't exist.

So when replacing 4116 DRAMs with 4164, make sure what kind of refresh 
your system supplies. If you don't know, use 4164 that only need 7Bit 
refresh. To find out, grab the datasheet.


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Received on 2016-10-12 15:00:03

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