Why would you do this? (Computer science-related)

[Supermercado]

One of my computer science textbooks has a question in it and I can't seem to come up with a good answer to it. Hoping someone here with more experience can help me with this.

Anyway, say you've got a two-bus system with a bus connecting the CPU to the memory and a bus connecting the CPU to the I/O devices, sort of like this:
memory -- CPU -- I/O

The question is why would you want to make it so the memory was central, with a bus connecting it to the CPU and a bus connecting it to the I/O? Like this:
CPU -- memory -- I/O

I'm sure it has something to do with speed or efficiency, but I can't find a good answer in the book. Anyone? Thanks.

Edit: Just need one reason.

 

[ScrapSilicon]

you asking for homework answers..

 

[vi edit]

Isn't that the idea behind agp?

 

[Supermercado]

Originally posted by: ScrapSilicon
you asking for homework answers..

No, actually, I don't think it's a homework question. Just one in the chapter.

 

[DaveSimmons]

Look up "direct memory access" in the index.

 

[ScrapSilicon]

gives the ability to calculate at very high speed

 

[Supermercado]

Originally posted by: DaveSimmons
Look up "direct memory access" in the index.

Ah. I knew it had to be something like that, but I couldn't figure out exactly what it was. Thanks

 

[FeathersMcGraw]

Originally posted by: SuperCommando

The question is why would you want to make it so the memory was central, with a bus connecting it to the CPU and a bus connecting it to the I/O? Like this:
CPU -- memory -- I/O

I'm sure it has something to do with speed or efficiency, but I can't find a good answer in the book.

Think about the relative speeds of main memory and I/O subsystems.

 

[XZeroII]

because everything must go from memory to the CPU, then back to the memory anyway.