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SeaGtGruff

3E Bankswitching?

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Can the Harmony do 3E bankswitching? As I understand it, this is a variation of 3F where writing to 3E switches a RAM bank into $F000-$F7FF, rather than a 2K ROM bank. I don't know the details of how this worked on actual 3E carts, but it would be cool if you could select from 256 different RAM banks by writing different values (0 to 255) to 3E. That would give you access to a maximum of 512K ROM by writing to 3F, plus a maximum of 256K RAM by writing to 3E. (I'm assuming a RAM bank would have a 1K write area and a 1K read area, as in E7 bankswitching.)

 

Michael

 

 

 

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Okay, I downloaded the source code and see a reference to 3E, so I take it the Harmony *can* do 3E bankswitching. So my question now is whether it does (or could be made to) allow access to multiple RAM banks by writing different values to 3E, the way that writing different values to 3F gives you access to multiple ROM banks? I don't know that anyone would ever need that much RAM in a game, but 512K ROM with 256K RAM sounds like an awesome idea. (And yes, I've read that Harmony currently goes up to only 32K ROM with 3F-- and presumably also with 3E?)

 

Michael

 

 

 

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It can do 3E, but the Harmony has just south of 32k flash and 8k RAM, so you don't want to store more than 14 to 3F or more than 6 to 3E. I don't recall offhand what the actual limits are (it's possible it's something like 16k/4k even) but I can check later.

 

Also worth mentioning is I've built special Melody boards with 128k flash and 16k, 32k, or 64k RAM and ran 3E on them (to demo an unreleased game that uses this scheme.)

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It can do 3E, but the Harmony has just south of 32k flash and 8k RAM, so you don't want to store more than 14 to 3F or more than 6 to 3E. I don't recall offhand what the actual limits are (it's possible it's something like 16k/4k even) but I can check later.

 

Also worth mentioning is I've built special Melody boards with 128k flash and 16k, 32k, or 64k RAM and ran 3E on them (to demo an unreleased game that uses this scheme.)

From your reply, I gather that it *is* possible to access multiple banks of RAM by storing different numbers in 3E. Cool! I've wondered about that ever since I first heard about 3E bankswitching. I've got an idea for a "Dragon Warrior" type game on the back burner, and I had thought to use 3E for it, but I didn't know if it was limited to 1K of expansion RAM or not, so that answers that question. Thank you!

 

Michael

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