DOS 16-bit OS and Win 2K 32-bit OS. What does that mean?

I understand the concepts of the CPU's register, data, and address busses. But when DOS is referred to as a 16-bit OS, and Win 2K a 32-bit OS, what does that mean?

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w^rl0rd

Anybody? Does it have anything to do with any of these busses?

cheeblie

I think the only difference is the fact that DOS only uses 16 bits of the bus. Any program written for DOS uses 16 bits, so on a 32 bit system you are only taking advantage of half of the throughput of the system. That would be my understanding.

Cheeblie

Webmaster

Here's an article that might help: www.accountingsoftwareadvisor.com/topics/32bit.htm

w^rl0rd

Thanks Webmaster, but where are these "lanes" he is talking about? Is he referring to the External Data Bus?

Webmaster

Virtually the entire mainboard, everything between the OS and the CPU.

w^rl0rd

So 32-bit instructions are being sent over a 64-bit data bus?
I really need to understand this. Can someone simplify it for me?

cheeblie

Haha, I find it funny that the article the Webmaster gave a link to was written by a CPA. What's next? A dentist telling us about SCSI? :P

Cheeblie

RussS

Shinobi - you really don't need to know it in any depth. Unless of course you are going to be working for a MoBo or Processor manufacturer.

The easiest way to think of this is to forget which bus is used. Think of 16/32/64 bit processing as a valve (or restrictor). You have a pipe (bus) that is 32 wide but your valve is only 16, then you have a restriction and things don't flow smoothly.
The operating system has to be able to handle this flow of information. If you loaded say Win 3.1 onto a whizzbang 64 bit processing system then it would always be running in a restricted mode.

Webmaster

cheeblie wrote:

Haha, I find it funny that the article the Webmaster gave a link to was written by a CPA. What's next? A dentist telling us about SCSI? :P

Cheeblie

Perhaps I was hoping no one would notice

w^rl0rd

Bellboy, I know I may not need to know this for the OS exam, but I feel that I should know this as an IT professional.

I understand the concepts of all of the busses, and I just want to know how they tie in.

Like DOS, for example; I know DOS can access upto 1 MB of address space, hence the 8086 & 8088 address busses being 20-bits. The only thing that is 16-bit about these processors is the registers and data bus of the 8086.

Do you guys see where I am going with this? Is it difficult to explain or just beyond the realm of my intelligence?

RussS

Like I said Shinobi - unless you are building MoBos or Processors you will never need to know the subject in anywhere that depth. A quick discussion with the three tutors here and none of them have a definative answer. One of these guys is a reasonable programmer and knows most things fairly indepth, but says he is at a loss as to why anyone needs to know this.
His comment was that is was like a doctor - knows about DNA and the basics of how it works, but does not need to know how to read a DNA stream as that is a specialist field.

Webmaster

This is simply not harder than it seems, a 16-bit OS can process 16-bits (in parallel) per clockcycle, hence you need a 16-bit cpu minimum. What exactly is your final question?

Drakonblayde

The Pentiums and it's competitors have a 64-bit external data path, but only a 32-bit internal data path. They can receive two 32-bit instructions and process them in the same cycle (there's more to it than that, but that's it in a nutshell).

w^rl0rd

Webmaster wrote:

What exactly is your final question?

My "final question" is what I asked all along Webmaster: DOES 32-BIT HAVE ANYTHING TO DO WITH THE CPU'S DATA BUS?

Sorry if you are frustrated with the question. I'll try not to throw fastballs at you anymore.

Thanks.

Webmaster

Don't get me wrong, I don't mind your question at all. I have the same habbit... when you want to know something, you really want to know it. Although RussS is right in saying that you probably don't need to know this in detail for most jobs, but 64-bit OSs and higher are already available and with no doubt there will be x kilo, mega or giga bit OSs even, in the future. anyway...

I just wanted to know the exact question... which I believe is: DOES 32-BIT OS HAVE ANYTHING TO DO WITH THE CPU'S DATA BUS?

I'm not an expert on this, but I guess no would be a better answer than yes, the one does not define the other. But you would need at least a 16-bit data bus to run a 16 bit OS.