What's the Highest Settings for Batari/Melody Cart?

[+Gemintronic]

Eventually I want to have a real game on a real cartridge. My questions is, what is the most storage/RAM/feature laden a cart can get can still be compatible with Batari and Melody cart? It seems like Batari and Harmony/Melody might support SuperChip and up to 32k games. I'm talking about the limitations of both Batari and Melody/Harmony here.

[+batari]

That depends. A stock Harmony/Melody has 32k of directly accessible ROM space and 8k of RAM. We can build a special Melody that allows up to 128k ROM and 64k RAM.

 

Alternatively, a stock Harmony has an EEPROM chip with around 400k of free space on it, and Melody can be fitted with the same EEPROM chip or alternatively, an EEPROM with up to 4 MB of space. The EEPROM is not directly accessible, as its data needs to be copied to RAM to be used, but you could copy an entire 4k and use it as a regular bank. The copying of data takes some time so it probably can't be totally transparent, but it could be useful for something like game levels. Granted, we haven't yet provided an easy way to access this space but we will in the future.

Edited July 4, 2010 by batari

[SeaGtGruff]

We can build a special Melody that allows up to 128k ROM and 64k RAM.

That sounds awesome! How much would something like that cost?

 

Michael

[+Gemintronic]

That depends. A stock Harmony/Melody has 32k of directly accessible ROM space and 8k of RAM.

 

Thanks for the response! Does this mean that Batari itself (as of 7/4/10) is limited to:

 

set romsize 32kSC

 

Which means 8 4k banks of ROM and 128 bytes of RAM with SuperChip extensions for playfield?

 

Whereas assembly gurus can take advantage of the full 32k ROM (400k with workarounds) 8k RAM and DPC chip features?

Edited July 5, 2010 by theloon

[+batari]

We can build a special Melody that allows up to 128k ROM and 64k RAM.

That sounds awesome! How much would something like that cost?

 

Michael

The chip needed for 128k/64k costs about $7 more than the regular chip on Melody. A chip with 128k/16k is available for about $4 more. However, we don't have these chips in stock and need to special order them, so there might be a slight markup above that if unless we had a good reason to make 25 or so.

 

 

That depends. A stock Harmony/Melody has 32k of directly accessible ROM space and 8k of RAM.

 

Thanks for the response! Does this mean that Batari itself (as of 7/4/10) is limited to:

 

set romsize 32kSC

 

Which means 8 4k banks of ROM and 128 bytes of RAM with SuperChip extensions for playfield?

 

Whereas assembly gurus can take advantage of the full 32k ROM (400k with workarounds) 8k RAM and DPC chip features?

Right now, yes. However, I plan to make DPC features available to bB sometime.

[SeaGtGruff]

We can build a special Melody that allows up to 128k ROM and 64k RAM.

That sounds awesome! How much would something like that cost?

 

Michael

The chip needed for 128k/64k costs about $7 more than the regular chip on Melody. A chip with 128k/16k is available for about $4 more. However, we don't have these chips in stock and need to special order them, so there might be a slight markup above that if unless we had a good reason to make 25 or so.

I'm thinking in terms of an RPG, so extra ROM would probably be more critical than extra RAM. I haven't studied the programming aspects of the DPC+ mode yet, but the overload option, or whatever it's called, is particularly interesting, where you can LDA # and STA zp in 5 cycles.

 

Michael

[+batari]

We can build a special Melody that allows up to 128k ROM and 64k RAM.

That sounds awesome! How much would something like that cost?

 

Michael

The chip needed for 128k/64k costs about $7 more than the regular chip on Melody. A chip with 128k/16k is available for about $4 more. However, we don't have these chips in stock and need to special order them, so there might be a slight markup above that if unless we had a good reason to make 25 or so.

I'm thinking in terms of an RPG, so extra ROM would probably be more critical than extra RAM. I haven't studied the programming aspects of the DPC+ mode yet, but the overload option, or whatever it's called, is particularly interesting, where you can LDA # and STA zp in 5 cycles.

 

Michael

An RPG might work with an EEPROM instead of a different chip on the Melody board. Harmony has the EEPROM already and this same EEPROM could just be added to a Melody board if you were to use it in a game. EEPROM data needs to be loaded to be used and this might delay a frame or two, but this might be fine for an RPG.

 

As for LDA #/STA zp in DPC, when you enable this mode, right before the kernel, typically, Harmony/Melody looks for the LDA # opcode ($A9) and examines the operand to see if it's $00-$38 (IIRC.) If so, on the next cycle, it dispatches the contents of the DPC+ data register $00-$38 to the 2600 instead of the operand. It should be capable of some powerful kernels.