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Converting other cartridge formats
https://atarimax.com/flashcart/forum/viewtopic.php?f=3&t=198
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Author:  Shawn Jefferson [ Fri May 21, 2004 1:03 pm ]
Post subject:  Converting other cartridge formats

I have an 8Mbit flashcart and I was thinking how I might use it. I was thinking that with a larger cartridge you may be able to convert other cartridge formats to work with the 8Mb flashcart.

For instance, the 128Kb XEGS cartridge. From what I've been able to gather contains 16 x 8Kb banks, where the last bank is always mapped in at $A000-$BFFFF and the other 15 banks are mapped into $8000-$9FFFF by a write to $D5xx.

Is it possible to take a 128Kb XEGS image, chop the last bank out, and combine it with all the other banks and write those banks to the flashcart so that anytime a new chunk is banked it, the bank that is not supposed to move is still there?

Of course it takes more space on the cartridge, but we have 1MB to work with. We would also have to edit the image to make the proper bank accesses for the flashcart, but that should be too difficult should it?

If all this is doable, a script or program could be written to do it automatically for various cartridge formats.

Well, possible?

Author:  classics [ Fri May 21, 2004 3:40 pm ]
Post subject:  Re: Converting other cartridge formats

The only formats you could convert directly without making major modifications to the cart code are ones that also use a 8k A0-BF bankswitching scheme.

The flash cart images for SDX and Diamond GOS were done this way.

I have flash cartridge designs that are 100% XEGS compatible as well as being compatible with the old format and a few others, but i doubt there is enough demand to make another run of small flash carts in a new design.

People seem a lot more interested in larger flash carts and removable media carts.

Steve

Author:  Shawn Jefferson [ Fri May 21, 2004 3:50 pm ]
Post subject: 

Oh, the flashcart only uses $A000-BFFF? I didn't know that. I thought it used all the cartridge space.

There goes that idea then.

How does the bank switching of the 8Mb cartridge work?

Author:  classics [ Fri May 21, 2004 7:26 pm ]
Post subject: 

Shawn Jefferson wrote:
Oh, the flashcart only uses $A000-BFFF? I didn't know that. I thought it used all the cartridge space.

There goes that idea then.

How does the bank switching of the 8Mb cartridge work?


128 banks of 8k from A000-BFFF. Touch D500-D57F to activate a bank, touch D580 to turn off the cartridge.

Steve

Author:  Helten E [ Sat May 22, 2004 3:12 pm ]
Post subject:  OSS Supercarts

The OSS Supercarts use a similar bank switching mechanism to the Atarimax carts. I've put MAC/65 on a 1Mb flash cart with no code changes, and it should be possible to modify the bank selection code to fit several Supercart images on one cart.

Here's how it works: Supercarts have a permanently resident bank at $B000-$BFFF and use $D500, $D509 and $D501 (for MAC/65, anyway) to select between three different 4kB banks at $A000-$AFFF. A 1Mb flash cart uses $D500-$D50F to select between 16 8kB banks at $A000-$BFFF. Soo... A flash cart with banks 0, 9 and 1 each containing the relevant $A000-$AFFF code and the "permanent" $B000-$BFFF code will act just like a real Supercart. 8kB (1 bank) is "wasted" due to the copied code, but I think that's a worthwile tradeoff as long as the remaining 13 banks (on a 1MB cart) don't go to waste.

To fit several images on a cart the bank selection code of each image needs to be changed and (obviously) a menu program is required. Since each image takes three banks, MAC/65, Action!, Basic XL and Basic XE can all fit on one 1Mb cart with room to spare.

I'll probably do this eventually, unless someone beats me to it. Anybody? :)

Author:  TXG/MNX [ Mon May 24, 2004 5:59 am ]
Post subject:  Re: OSS Supercarts

Helten E wrote:
The OSS Supercarts use a similar bank switching mechanism to the Atarimax carts. I've put MAC/65 on a 1Mb flash cart with no code changes, and it should be possible to modify the bank selection code to fit several Supercart images on one cart.

Here's how it works: Supercarts have a permanently resident bank at $B000-$BFFF and use $D500, $D509 and $D501 (for MAC/65, anyway) to select between three different 4kB banks at $A000-$AFFF. A 1Mb flash cart uses $D500-$D50F to select between 16 8kB banks at $A000-$BFFF. Soo... A flash cart with banks 0, 9 and 1 each containing the relevant $A000-$AFFF code and the "permanent" $B000-$BFFF code will act just like a real Supercart. 8kB (1 bank) is "wasted" due to the copied code, but I think that's a worthwile tradeoff as long as the remaining 13 banks (on a 1MB cart) don't go to waste.

To fit several images on a cart the bank selection code of each image needs to be changed and (obviously) a menu program is required. Since each image takes three banks, MAC/65, Action!, Basic XL and Basic XE can all fit on one 1Mb cart with room to spare.

I'll probably do this eventually, unless someone beats me to it. Anybody? :)


I will not beat ya 8) just do it :lol:

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