AuthorTopic: What exactly is 8-bit?  (Read 4796 times)

Offline TheMonsterAtlas

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What exactly is 8-bit?

on: September 17, 2012, 10:05:27 pm
I'm probably repeating something that has already been posted here but I'm not quite sure as to what exactly is defined as 8bit. I know Super Mario Bros. 3 and etc are 8bit, but why are they? I know those games are more than 1 byte of code. Does it have something to do with colors?

Offline Dusty

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Re: What exactly is 8-bit?

Reply #1 on: September 17, 2012, 10:28:51 pm
I know Super Mario Bros. 3 and etc are 8bit, but why are they?
Because the NES was an 8-bit console. I'm pretty sure though the CPU was an 8-bit processor and it actually didn't really reflect graphics that much, if at all. But the 8-bit may refer to the overall palette of the machine, but I don't think NES had a 256(8-bit) color palette.

However I guess I'll leave it to the people around here who are more in-the-know about the technical side of these things.

Offline TheMonsterAtlas

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Re: What exactly is 8-bit?

Reply #2 on: September 17, 2012, 11:17:08 pm
Yeah, I think it says the NES had like 48 colors and 6 grays @__@

« Last Edit: September 17, 2012, 11:39:28 pm by XLR8ED »

Offline Kasumi

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Re: What exactly is 8-bit?

Reply #3 on: September 18, 2012, 12:05:56 am
I don't like 8-bit/16-bit used for describing graphics. People call Atari graphics 8-bit. People call NES graphics 8-bit. One is clearly very far ahead of the other. Bits per pixel is more descriptive as far as graphics go, but even that's not perfect.

I guess X-bit generally refers to the largest size number most of the CPU registers work with, but even that doesn't say a lot about how powerful a CPU is or what you can do with it. NES deals with 16bit addresses. There's nothing stopping it from working with 16 bit, or 24 bit numbers, higher bit numbers.

I don't think it's a very good descriptive term for much of anything the general public uses it for, but I guess a computer science major might have more to say about it.
I make actual NES games. Thus, I'm the unofficial forum dealer of too much information about the NES

Offline TheMonsterAtlas

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Re: What exactly is 8-bit?

Reply #4 on: September 18, 2012, 12:15:08 am
Well aparently what was stopping it from using so many colors was that the processor could only put a number of colors up on the screen at once. 25 for the NES to be specific. I can't really find any other information about the different 8-bit consoles.

Offline ptoing

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Re: What exactly is 8-bit?

Reply #5 on: September 18, 2012, 02:53:03 am
Doesn't the bit value of a processor have to do with the maximum amount of opcodes? Like an 8bit processor has a possible 256 opcodes at max. Something like that.

But yeah, even in graphics alone 8-bit is ambiguous. It could mean either Bitdepth, which in itself does not say much either, because it could be distributed in different ways, if the hardware was layed out like that. Or it could mean the amount of colours on the index.

Also a lot of systems use mixed bit ranges. The PC-Engine has an 8bit processor, but the graphics chip is 16bit.
There are no ugly colours, only ugly combinations of colours.

Offline Ai

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Re: What exactly is 8-bit?

Reply #6 on: September 18, 2012, 04:56:06 am
Kasumi, that's mostly right. I guess the way to say it is that an N-bit cpu is designed to mostly manipulate N-bit values. Like you said you can handle bigger values but it's harder and slower (eg. manipulating 64-bit values on a 32-bit processor is slower than on a 64-bit processor)

Wikipedia says:
Quote
Eight-bit CPUs use an 8-bit data bus and can therefore access 8 bits of data in a single machine instruction. The address bus is typically a double octet wide (i.e. 16-bit), due to practical and economical considerations. This implies a direct address space of only 64 KB on most 8-bit processors.


@XLR8ED: Rendering is often done by a separate processor, so it's not easy to say 'Right, that's an 8-bit machine, so it can't have that many colors'. If you look at, for example, the MSX2, it had a 256-color mode, and the 2+ had HAM-like 19k/12k-color modes, plus sprites, but the CPU was just an 8bit Z80.
BTW, Wikipedia has a 'list of videogame consoles palettes' page which gives some of the info you want.
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Offline 9_6

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Re: What exactly is 8-bit?

Reply #7 on: September 18, 2012, 06:26:57 am
It probably means the same as for the 8-bit music kind: Looking/sounding like something from an old cosole..
I don't think it's oftenly used to accurately describe something on a technical level.
Does scaling an image blur it?
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Offline PypeBros

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Re: What exactly is 8-bit?

Reply #8 on: September 19, 2012, 09:39:29 am
Doesn't the bit value of a processor have to do with the maximum amount of opcodes? Like an 8bit processor has a possible 256 opcodes at max. Something like that.
Not necessarily. 8-bit processor can perform computation natively only on 8-bit quantities. Your programmer is going to shout at you if you ask for a resolution higher than 256x256 because he'll need to find room for the 9th bit of some coordinates. If you really insist, he's likely to ask you whether that would hurt the game play if characters and ennemies never move by less than 2 pixels at once (he's planning to store x/2 internally already :)

These system typically had small memory, addressable in chunks of 256 bytes. That means the 6502 for instance (NES, C64 and many others) has only access to 2 pages of 256 bytes at once: the "special 0 page" and one page you select by setting its value in a special register.

Typical restrictions for such systems would be "no more than 256 tiles in your charset" and "you've got 8 bits to code your character attributes". That could be e.g. one background colour picked between 0-15 and one foreground color.

I don't think it would be possible to really describe 8-bit "exactly" when it comes to graphics or sound beyond the overall description that it is either "highly quantized" or "picking analog functions among a limited set and combining them". The 8-bit SID music sounds quite different from the NES music, for instance, but they share the fact that people used arpeggio when they needed chords because there was no proper way to create music with 3-tone-chords on systems that had merely 4 sound channels.
« Last Edit: September 24, 2012, 02:44:23 pm by PypeBros »

Offline ptoing

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Re: What exactly is 8-bit?

Reply #9 on: September 19, 2012, 11:00:27 am
Ah I see. C64 is not quite 6502, it's 6510, very similar tho. And the SID has only 3 channels even. I think the NES has 5, but on the NES each channel is fixed to a waveform and one is reserved for samples or something.
There are no ugly colours, only ugly combinations of colours.