gtag('config', 'AW-10816673336'); How Oldschool ROM Cartridge Games Worked

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How Oldschool ROM Cartridge Games Worked



 In previous episodes we have discussed floppy disks and tape games.

And today, we’re going to talk about cartridge games!

The very first games were distributed on cartridge format for the Fairchild Channel-F, and soon

after on the Atari 2600.

ROM cartridges were used in all kinds of systems, such as the Speak and Spell, musical keyboards,

and even game systems as new as the Nintendo 64.

I have also invited the Obsolete Geek to come over and show you some of his collection.

[OG] So, I am a huge fan of cartridges and cartridge based systems.

Couple of my favorites, obviously the Neo Geo, an arcade based platform, which has absolutely

massive cartridges.

Which could be a little tricky to plug in.

Also, another one of my favorites, the turboGrafx, also known as the PC Engine in Japan, which

has these really cool credit card-shaped cartridges.

Also very unique.

[8BG] As a kid with my Commodore VIC-20, I was obsessed with trying to copy a game cartridge to tape.

You see, I believed that the game was somehow loaded into the computer's memory much like

a game would be from disk.

And I had noticed that if I pulled out the cartridge game while the computer was on,

[buzzing]

I noticed that every now and then when I'd pull the cartridge out, the computer would

return to a READY prompt.

And so then I would attempt to save the game to a tape.

Of course, it never worked.

And the main reason it didn't work is due to my complete mis-understanding of how these

games worked.

So the 6502 processor could only access 64k of memory.

So, for these examples I'm going to be talking mostly about the Commodore VIC-20, because

it has a simple memory map that's really easy to understand.

So you might imagine the memory map looking something like this.

Keep in mind there are two types of computer memory: RAM known as Random Access Memory,

and of course, ROM, known as Read Only Memory.

So, the VIC-20 only had 5K of RAM, and thus the memory map looked more similar to this.

So the Kernel and BASIC ROM were at the top of the memory map and the 5K RAM was at the

bottom.

There was a lot of empty space where if the processor tried to read and write to that

area, there was simply nothing there.

So when you insert a cartridge, it literally adds this additional memory into the main

memory map of the computer, adding to the total amount of memory in the system.

In this case an 8K game cartridge is adding read-only-memory, but you can also add an

8K memory expansion cartridge which will add RAM to the machine instead.

Some cartridges even had 16K of ROM or RAM.

But once the cartridge is removed, the information is no longer visible to the CPU, hence why

I was never able to save those pesky game cartridges to a tape or disk as a kid.

Now on a modern computer, most of us are familiar with what it looks like to add some RAM expansion.

But, aside from the BIOS chip, modern computers really don't have any ROM chips or ROM sockets,

because they pretty much expect all software to be loaded from either disk or USB or something

like that.

So even though the VIC-20 has 5K of RAM, it really can only use about 3.5K because

the rest of that memory is used for screen memory and some other kernel functions.

So if you load a game from tape or disk, the maximum size of that game will be limited

to about 3.5K. And these sort of games loaded into the VIC were usually extremely primitive

games.

But a cartridge game can be as much as 16K.

And so the games can be considerably more complex, with more graphics, etc.

So in the case of the VIC-20, cartridge games were usually better.

[Ms. Pacman music playing]

So that’s the Commodore VIC 20, but a few years later the Commodore 64 came out with

64K of RAM and this changed things up a bit.

You see, a cartridge in the C64 is still limited to 16K.

And the games that were on these cartridges weren't neccessarily bad, but they were limited

mostly to the classic type arcade games.

But when you load a game from disk, suddenly you can use almost all of the machine's 64K

which means the games become even more rich and complex.

The original Atari computers tell a similar story.

The 400 and 800 both shipped with 8K of RAM, so the vast majority of games were released

on cartridge.

These systems were designed with the slot on top much like a game console, which suggests

they expected most games would be on cartridge.

So interestingly enough, the Atari 800 actually has two cartridge slots, one of them is labeled

left cartridge and the other is labeled right cartridge.

Now, all of the cartridges I have are are actually- they say “left cartridge” right

on the ROM cartridge.

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