[Coco] Fwd: Re: 32K carts? Arkanoid etc

[Joef6809]

Ok it looks like Arkanoid does use 32K external mode. Heres the trace of all 
writes to port 0xFF90:
0: writing port 90 with A
1: writing port 90 with CE
2: writing port 90 with CA
3: writing port 90 with C8
4: writing port 90 with CA
5: writing port 90 with CE
6: writing port 90 with CC
-------Loaded card here-----------
7: writing port 90 with A
8: writing port 90 with CE
9: writing port 90 with CA
10: writing port 90 with C8
11: writing port 90 with CA
12: writing port 90 with CE
13: writing port 90 with CC
14: writing port 90 with 7F

Is there any special way you are writting to the memory card? It seems 
arkanoid is "copy protected". It seems to try to overwrite itself twice!
If your cart just allows direct writes to memory locations then I'm sure 
thats your problem.



----- Original Message ----- 
From: <flexser at fiu.edu>
To: <coco at maltedmedia.com>
Sent: Monday, October 22, 2007 4:50 PM
Subject: [Coco] Fwd: Re: 32K carts?


> Joe, I'm not sure about the cartridges you mention, but some large 
> cartridge games used a bank-switching scheme that relied on circuitry 
> inside the cartridge to switch between 8K banks of ROM within the 
> cartridge by poking a bank number into $FF40(?) to access different parts 
> of the code.  You might take a look at the game's code to see if you see 
> anything that looks like that.  They may have avoided using the 32K 
> external mode in order to be able to run on the CoCo 1/2.
>
> Art
>
> ---- Original message ----
>>Date: Mon, 22 Oct 2007 13:21:36 -0400
>>From: "Joe" <joef6809 at gmail.com>
>>Subject: Re: [Coco] 32K carts?
>>To: "CoCoList for Color Computer Enthusiasts"
> <coco at maltedmedia.com>
>>
>>It seems to work like this.
>>When the gime is set to 16K Internal /16K External
> the internal rom runs
>>from $8000 to $C000 and the External rom runs from
> $C001 to Whatever. We all
>>know that. When you switch to 32K External it gets
> wierd.
>>$C001 to Whatever is mapped to the first 16K of the
> ROM and $8000 to $C000
>>maps to the last 16K of the ROM. This makes sense
> as any code running from
>>rom say at $C??? would need to turn on 32K External
> mode, but when that
>>happens if it was a liner map the code that was
> executing would "jump up"
>>16K.
>>Hope I've explained this so others can understand.
>>When I get home I'll hack up a test version of VCC
> and see exactly what
>>Arkanoid is doing. IE what GIME registers its
> trying to hit.
>>
>>----- Original Message -----
>>From: "Roger Taylor" <operator at coco3.com>
>>To: "CoCoList for Color Computer Enthusiasts"
> <coco at maltedmedia.com>
>>Sent: Monday, October 22, 2007 11:35 AM
>>Subject: Re: [Coco] 32K carts?
>>
>>
>>> At 09:52 AM 10/22/2007, you wrote:
>>>>Hi guys,
>>>>
>>>>Is there anything special about a 32K cart?
>>>>
>>>>I'm trying to work out why I can't get Arkanoid
> or Rampage to run out of
>>>>EPROM on my cart board. I assumed the top 16KB
> would get mapped into $C000
>>>>and the ROM bootstrap code then enables the full
> 32KB of external ROM
>>>>space.
>>>>But it would appear to me that Arkanoid at least
> doesn't do this.
>>>>
>>>>What I think is happening atm is that when I
> enable the 32KB jumper on my
>>>>cart, the internal and external ROMs both drive
> when the CPU is accessing
>>>>memory from $8000-$BFFF and it's not a pretty
> sight... :(
>>>>
>>>>So I'm wondering how 32KB carts actually
> function?!?
>>>>
>>>>Regards,
>>>
>>>
>>>
>>> That's something I never learned, but it seems
> that the internal CoCo 3
>>> ROM area from 32768 to 49151 is there no matter
> what, and a 32k pak might
>>> have to switch in 16K at a time starting at
> 49152/$C000, no?
>>>
>>> Hopefully you can add a jumper or two on your
> boards to fix any problems
>>> like this.
>>>
>>>
>>>
>>>
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>>
>>
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