5 replies to this topic

[4ever2600]

What was the difference between the CBS ram plus cart and Atari using their Sara Chip on certain games? The way I understand both are the CBS Ram plus carts gave the 2600 game more Ram (like 4k) to give additional workspace to operate a better game... Same with the Sara chip. How much difference was there between Sara and CBS chip? Any better explaination would help! Thanks! - D

[djmips]

The are very similar. SARA gives you an extra 128 bytes of RAM while RAM+ gives you an extra 256 bytes of memory.

In SARA the writing happens from addresses $1000 to $107F (the first 128 bytes) and the reading is from $1080 to $10FF (the next 128 bytes).

RAM+ is similar but the writing happens from adresses $1000 to $10FF (256 bytes) and the reading is from $1100 to $11FF (the next 256 bytes).

I've recently coded a game/demo using the Super Chip RAM (SARA) and it was quite straightforward to use. The method I used, which worked quite well, was to code/debug a routine using zero page RAM and when it was working well, I methodically converted the code to use the SARA RAM. Converting all writes to use the lower addresses and the reads from the upper addresses.

Some sample code in bBasic and ASM.

 dim enemyXW			= $1000
 dim enemyXR			= enemyXW + 128
 dim enemyVelW		  = enemyXW  + 2
 dim enemyVelR		  = enemyVelW + 128

  enemyXW[ii] = enemyXR[ii] + enemyVelR[ii]

  ldy #$00
  lda (boltPtr),y
  adc enemyXR
  sta missile0x
  iny

[4ever2600]

That's exactly what I wanted to know... That sums it up perfectly! Thanks again dj! Later! - D

[SeaGtGruff]

4ever2600, on Tue May 8, 2007 9:03 PM, said:

What was the difference between the CBS ram plus cart and Atari using their Sara Chip on certain games? The way I understand both are the CBS Ram plus carts gave the 2600 game more Ram (like 4k) to give additional workspace to operate a better game... Same with the Sara chip. How much difference was there between Sara and CBS chip? Any better explaination would help! Thanks! - D

Although djmips already answered your question, here's a little bit more information:

The CBS RAM+ cartridges have 12K ROM-- or three 4K banks-- with 256 bytes of extra RAM.

The Superchip (or Sara chip) cartridges can have different sizes-- 8K ROM (two 4K banks), 16K ROM (four 4K banks), or 32K ROM (eight 4K banks)-- with 128 bytes of extra RAM.

So the CBS RAM+ cartridges have twice as much extra RAM as the Superchip cartridges do, but the Superchip cartridges can come with more ROM than the CBS RAM+ cartridges have.

Michael

[4ever2600]

That's cool! I wondered that one myself... I thought that but I wasn't positive... Thanks for the extra info! Later! - D

[Gorf]

You all forgot to mention the hopefully soon to be a reality, 4A50.

32k RAM/128k ROM.

one could do a "MYST" (of sorts) with that much memory.