Cart Question

[Wrathchild]

Is a 256K cart possible, I know of the 128K and 512K carts.

I guess one could use a 512K board and keep the high address

line low, or just never address those banks though $D500?

 

Or are the 256K PROMs any harder to get hold of?

 

Reason being, I'd like to put all the Brian Howarth 'Mysterious Adventures'

on one cart, and it comes out to exactly 248K, plus the 8K interpreter = 256K!

 

ftp://ftp.ifarchive.org/if-archive/scott-...ious_inform.zip

 

Thanks,

 

Mark

[Tickled_Pink]

Used EPROMs are relatively easy to get hold of through eBay (got a pile from there a few months back). Think I might have some 256K chips. HOWEVER ... you do realise that 256K = 256K bits when you're talking about EPROMs? i.e. a 256K EPROM = 32K bytes.

[Sheddy]

Mark,

 

there's always the "Megacart" format - supports upto 8Mbits=1MByte=1024K in 64 16K banks, or the XEGS format, which supports the same, albeit not fully switchable, in 128 8K banks. 256KB is one of the possibilities for both.

 

Much more info in the Atari800WinPlus help under "Cartridge images (CAR, ROM, BIN)" and Jindroush's

 

As to how to actually physically build these things, I'm sorry I have no idea! Sunmark (Super Genius) are making Megacarts, so they may be able to give you some pointers. I believe they use just the one chip even for even the biggest carts.

 

Nice work by the way - I can't believe how many games you've converted or made XL/XE compatible recently. Thanks!

[Wrathchild]

Used EPROMs are relatively easy to get hold of through eBay (got a pile from there a few months back). Think I might have some 256K chips. HOWEVER ... you do realise that 256K = 256K bits when you're talking about EPROMs? i.e. a 256K EPROM = 32K bytes.

 

Yep, bits & bytes has been done to death already...

 

If bulk Eproms end up cheaper from Ebay than getting new Proms

then then that's an idea, thanks. Though wiping them all could get boring.

Don't see many used Proms on Ebay though?!

 

Thanks!

 

Your welcome, I think I got a little miffed that these carts were

coming out with no effort to either fix the problem, or put a

translator on the cart too. (not as miffed as those XL owners

with those carts now that we've fixed 'em )

 

I mentioned in the Infocom interpreter thread that I kind of

prefer the XEGS switching method, but either is easy enough

to work with. I do have access to PCB layout and prototyping

but we're kinda busy on a non-Atari projects at the moment.

When we're ready I'd have to fund the mastering of the board

and then you can have runs of these professionally done at any

stage. Sunmark may want to comment here as they've been

through it already. That initial outlay could take a little while to

get back, the programming (from my thinking) would go in for

free or a small percentage of each cart sold.

 

Where's this leading... it would be nice to do the Infocom carts,

but I'm happy enough to make the menu/images as I've a fair

idea of how I'd lay these out , about 5 carts of 512KBytes each.

In the next few weeks I may get around to finishing working out

replacing the Eidolon's level loader with a ROM bank routine.

And then of course Elite will have to go onto cartridge

 

Mark

[Super-Genius!]

Hi Mark,

 

Nir Dary and myself designed a 1M board [1M x 8] a while back.

We usually use 512K EEPROM's for most applications. We would be

glad to help you out!

 

The way the bankswitching works is as follows:

 

The cartridge works this way: When you write $00 to $7F into address $D5xx it will map a 16k bank into $8000 - $BFFF.

 

For example, writing $00 to $D5xx will show the first 16k of the EPROM at $8000 - $BFFF. When you write $01 to $D5XX the second 16k bank of the EPROM will show at $8000 - $BFFF.

 

If you write $80 to $d5xx the cart will be "switched off" and the original RAM will show at $8000-$BFFF.

 

Here is a picture of the board with a 512K EEPROM:

 

 

Here are the instructions to modify the board for a 1M EEPROM:

 

http://www.mega-cart.com/modify.html

 

I am finishing up a 2M [2M x 8] using a new bankswitching technique...

 

Mark