[Coco] 32K carts?

[jdaggett at gate.net]

The internal ROM in the Coco 3 is a 27256. 

james

On 23 Oct 2007 at 10:48, Joe wrote:


> That is interesting. I wonder now if all the 32K images floating

> around the net are backward like that. When I was working on getting

> these running I jut assumed the images were correct and my MMU

> emulation was off. now I'm not sure. I've got a real Rampage! cart.

> Does anyone know if the chip inside it is pin compatible with a 27256.

> I'll try to pry it out and read it on an external Eprom programmer.

> 

> 

> ----- Original Message ----- 

> From: "Mark McDougall" <msmcdoug at iinet.net.au>

> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>

> Sent: Tuesday, October 23, 2007 5:37 AM Subject: Re: [Coco] 32K carts?

> 

> 

> > Joe wrote:

> >

> >> 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.

> >

> > Thanks Joe - that's done the trick. I had to swap the upper and

> > lower 16KB in Arkanoid and it runs now! Presumably Rampage has the

> > same issue.

> >

> > I need to order a couple of more passives now to be able to test the

> > flash option and the "Flash2" cart.

> >

> > For those few interested, I'll do some pricing very soon. I've been

> > ultra-busy the last few weeks and have only been able to devote the

> > odd minute here-or-there to this project...

> >

> > Regards,

> >

> > -- 

> > |              Mark McDougall                | "Electrical Engineers

> > do it |  <http://members.iinet.net.au/~msmcdoug>   |   with less

> > resistance!"

> >

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> > Coco at maltedmedia.com

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> 

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