Idea: creating a ram cartridge for Atari 5200

[Wilheim]

Hi, all!

 

I tried to convert The Goonies for Atari 5200, and I realized that having 16 kbytes Ram could be not enough. It needs at least 15 kbytes for screen swapping.

 

Considering this, I was thinking in creating a ram cartridge with the following behavior:

 

1. Use $4000-$7fff as a ram area.

2. Use $8000-$bfff as:

    a. $8000-$9fff as ram.

    b. $a000-$bfff as a bank-switching using bus address with a7 as a ram switch.

 

that way, we would get a maxflash compatible bank-switching and it would be easier to convert games such as Goonies, Conan, spy vs spy and others. Of course, there is also needed to change the joystick routines and hardware chips locations.

 

what do you think about it?

[Rybags]

A barrier to progress there is that for whatever stupid reason, just like the 2600 the 5200 has no /W line on the cartridge port, though it does appear on the expansion connector.

 

As for configuration ideas - yeah, a cartridge with decent amount of Ram and flash that could act in different ways would be a cool idea.

Like default to having Rom with the startup vectors appearing where they need to be, then allowing bankable config of flash and Ram in various ways in 16K chunks in the $4000 and $8000 areas.

[Wilheim]

Oh, gosh! Why didn’t think about it? Even having a least two free pins! By the way, what about phi2?

 

maybe we could set a new standard and add a r/w line in one the free pins. That means that every 5200 must be modified to add this pin. Maybe it’s too ambitious.

 

What do you think?

Edited January 17, 2021 by Wilheim

[Wrathchild]

Steve/Classic did this with the Atari 5200 Ultimate SD Multi-Cart but from what I remember it may have an issue with not being a 100% reliable method, for example if wanting to take a bus-sniffing approach such as with the UNO cart

[_The Doctor__]

how about making cartridge for the expansion connector instead? or put the memory on the expansion connector if possible.

[Wrathchild]

From what I recall of it the 'window' is too small to be of practical use

[Lynxpro]

On 1/25/2021 at 2:51 PM, Wrathchild said:

From what I recall of it the 'window' is too small to be of practical use

 

Get CPUWiz in on the discussion. He's made mention several times of the limitations of the bandwidth of both the 5200 and 7800 Expansion Ports.

 

The 5200 Expansion Port was supposedly going to be used to interface a musical keyboard with the 5200 since the Intellivision and C64 had similar "educational" products available for it. Might that allow for a regular keyboard to be connected? [then again, a keyboard probably would register multiple keystrokes at the same time than a musical keyboard so that might be a bandwidth issue]. I assumed a joystick adapter might be possible since fire buttons and joystick movements might not take up a lot of bandwidth [and reminiscent of the Amiga/Atari ST Parallel Port Joystick Adapters] but I think CPUWiz said that wouldn't be possible. Then again, that might've been in relation to the 7800 Expansion Port...

 

I think when this last came up in the regular 5200 Threads, he suggested a cartridge with a 16K ROM bank - or was it a 32K ROM bank? - separate from the main ROM in the cartridges as a means of porting A8 games that required 64K RAM originally. 

 

Before he passed, Curt and I had discussed the idea of a plug-in expansion board into the ANTIC socket that could provide the 5200 with extra RAM and a PIA chip. That was his idea on how to get the 5200 a decent amount of RAM and SIO functionality so modern larger A8 games could be ported without much fuss as well as possibly porting MIDI Maze over...