Re: Could you make a 'new', 'better' computer from the C64 just by reprogramming the PLA?

From: Claudio Sánchez <tokafondo_at_gmail.com>
Date: Wed, 3 Nov 2021 21:37:39 +0000
Message-ID: <064798d6-6531-93e0-3e25-9c0d9041fcdc_at_gmail.com>
> VIC2 cannot use color ram in DRAM at all.  The VICII data bus is 12
> bits wide, but is shrunk to 8 bits during cpu cycles by a 2x4 (4066)
> switch to allow the cpu access to color memory.  Using DRAM for color
> memory would require adding more DRAM to the system.
  
I think that was a solution of compromise so they could stop tinkering with the address decoding logic. Why should it be a problem to have color RAM mapped in DRAM in the first place? They had to include a SRAM chip in *every* computer (later revisions would have it included in that SHARP chip).

  
> On Wed, Nov 3, 2021 at 5:23 PM Claudio Sánchez <tokafondo_at_gmail.com> wrote:
>>
>>> You can already access the dram underneath color ram.
>>>
>>> VIC2 cannot use dram for color ram by reprogramming the PLA.
>>
>> It has a direct connection, hasn't it?
>>
>>> On 02/11/2021 09:39, Tokafondo wrote:
>>>> What about the color RAM? How to access the real RAM underneath? Could
>>>> reprogramming the PLA allow using DRAM instead of SRAM?
>>>>
>>>
>>
> 
Received on 2021-11-04 00:00:03

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