PBI vs Cartridge

[Timothy Kline]

Good evening, everyone,

 

I've been wondering, especially since Dropcheck has started inquiring about the Atari's PBI, what the advantages and disadvantages are between the PBI and the cartridge interface itself? What types of devices are best suited for one I/O platform over the other?

 

I imagine from a modding perspective, a cartridge-based mod would have a much broader usability factor since not every Atari 8-bit has a PBI interface— but every Atari DOES have a cartridge port!

 

For me, the primary drawback to these cartridge-based mods is that you only get to have one mod in play at a time. While there are a few pass-thru mods, the reality is that I don't see my utilizing the USB cartridge, the Bluetooth cartridge, and my SpartaDOSX cartridge with MacRorie's R-Time8 cartridge all in a single session, even though that would be something I totally seem myself utilizing.

 

Yet all of these could be in simultaneous use, should someone develop an interface along the lines of the 1090, where the USB cartridge would become a PBI card-based solution, as would the Bluetooth cartridge— both operating through the PBI lines. And wouldn't it be convenient to be able to set something like the RapidUS to card-based, as well?

 

However, with the 65/130XE and their ECI port, it seems like any 1090-like expansion solution would need to support a cartridge port.

 

Anyhoo, I was just wondering what the technical advantages and disadvantages were between the PBI and the cartridge interface insofar as mod development is concerned...?

 

Submitted for your perusal and consideration,

Tim

[Kyle22]

I'd love to see some new ideas take the form of an 800 card with a PBI connection for Incognito users. A very short ribbon cable and a pass-through PBI port on the other side of the card to provide for other cards or external PBI devices would be awesome.

 

The card slot can still provide power and physical stability for the upgrade.

We've got 3 open slots in there, let's use them!

[Rybags]

Cartridge generally has space restrictions so anything too big needs a breakout box/ribbon cable type arrangement. Less addressing versatility in that only the 16K window and 256 byte IO space window are available though bank switching overcomes that.

 

PBI/ECI allows full 64K addressing and control lines to effectively override inbuilt Ram or Rom. Though the shortcomings are there, several obviously needed control lines are absent which limits it's potential not to mention no power by default on 800XL although once a project goes over a few hundred mA you'd want to use a seperate PS anyway.

[Dropcheck]

Cartridge generally has space restrictions so anything too big needs a breakout box/ribbon cable type arrangement. Less addressing versatility in that only the 16K window and 256 byte IO space window are available though bank switching overcomes that.

 

PBI/ECI allows full 64K addressing and control lines to effectively override inbuilt Ram or Rom. Though the shortcomings are there, several obviously needed control lines are absent which limits it's potential not to mention no power by default on 800XL although once a project goes over a few hundred mA you'd want to use a seperate PS anyway.

 

 

You mentioned that several control lines are missing. What control lines would be needed on which machine?

[Rybags]

Looks like we have 3 almost identical threads going on about this stuff.

 

This type of thing has come up before when talking of current and proposed enhancements.

PBI has some stuff that should have remained for ECI and likewise the other way. And like I mentioned elsewhere some stuff well intentioned but probably done the wrong way.

 

D1XX - it's only telling you that entire page has an access going on so you'd still need further decoding. So a better alternative would have just been to replicate /IO from the MMU, then leave it to the peripheral to deduce the remainder.

 

/HALT - nicely provided on ECI but missing on PBI. We want to be able to halt the CPU so that a device can do DMA writes to Ram, e.g. blitter, DMA audio playback or DMA mode HDD.

 

/AN0-AN2 - if we have the Antic command lines then a peripheral to an extent would be able to predict Antic DMA patterns which could be helpful for numerous things. Would also allow replicating the Antic video component externally.

 

Audio out would probably be helpful as well, allow mixing Pokey audio with an external device for stereo rather than having to internally modify the machine.

Edited October 26, 2016 by Rybags