Address/Data lines

[gamer4life]

In a microprocessor class I took in college, we were working with the Motorola HC6811.
This had 16 address lines and 8 data lines. (i.e. 16 bit processor)

Does the AMD64 have 64 address lines and 32 data lines?

 

[Matthias99]

First off, the number of address lines depends on the memory controller, not the CPU (although with the Athlon64s, the memory controller is on-die). The AMD64 chips actually address 48-bit (I think) memory spaces, not a full 64 bits (which would be a tad bit of overkill on today's, or even tomorrow's, systems), but can work natively with 64-bit data items. So they would have 64 data lines and 48ish address lines.

I would call the CPU you described an 8-bit processor with a 16-bit memory controller, not a 16-bit processor.

 

[gamer4life]

You're right, I meant 8 bit processor.

So with 64 data lines that means the cpu can read/write to memory 8 bytes at a time?

 

[imgod2u]

Memory subsystems aren't exactly limited by the largest chunk of data modern processors have. Since most modern processors are superscalar (at least, with x86 they are), they can take in multiple chunks of data at any given time. The address lines is still limited by the processor's address space (or rather, the memory controller's addressing capabilities). However, the data lines can be almost as wide as you want to make it. For instance, on the P4, the data bus is 64-bits wide. On Opteron, it's 128-bits wide.

 

[Mark R]

The HC11 has an 8 bit internal data path - so it is termed an 8 bit processor. The width of the address bus defines the amount of memory that is addressable, and not the processing capability of the CPU, so doesn't factor into this. The HC11 has a 16 bit address bus, the P4 has 36 bits, the Athlon 64 40 bits.

The Athlon64 has a 64 bit data path - it can perform operations on 64 bit data in one go. This is not to be confused with a Pentium 4, which has a 64 bit data connection to the motherboard, but is only a 32 bit CPU, because it is only capable of working on 32 bits in one go. Because the P4 can operate internally so much faster than the Mobo can, there is a bottle neck at the chip's pins: using more pins helps alleviate this, but doesn't affect the internal operations significantly.

 

[Sahakiel]

Ah, the memories. We worked on a HC12, the 16-bit upgrade to your HC11.

 

[itachi]

So with 64 data lines that means the cpu can read/write to memory 8 bytes at a time?

this is where it may get kinda confusing.. typically when the data bus width is rated it's rated by the number of bits it can read or write. since amd's single channel 64-bit processors can read and/or write at the same time.. it's considered to have a 128-bit data bus, which would yield 16 bytes.. however, since it can't read or write twice at the same instant it's not exactly true to being 128-bits wide.

..For instance, on the P4, the data bus is 64-bits wide. On Opteron, it's 128-bits wide.

p4 with dual-channel has a 128-bit wide bus.

Because the P4 can operate internally so much faster than the Mobo can, there is a bottle neck at the chip's pins: using more pins helps alleviate this, but doesn't affect the internal operations significantly.

mm.. you don't know what you're talking about. the p4 isn't the only processor out there with that bottleneck and to make such a statement proves your ignorance. any and every processor that has the cpu running at a different speed than the memory has a bottleneck at that point. the fact that the p4 is 32-bits only means that the general purpose registers are 32-bits wide.. so up until data reaches those registers, it won't be any different than if the p4 was a 64-bit processor.

The AMD64 chips actually address 48-bit (I think) memory spaces, not a full 64 bits (which would be a tad bit of overkill on today's, or even tomorrow's, systems)

yea, amd64 has a 48-bit address bus.. so do some of the p4's. only problem is.. you can't turn "on" the extra 16-bits without an operating system that supports pae (physical address extensions)- pretty much windows server os' only.
on another note.. a system that fully utilizes 64-bits would be awesome! 2 exabytes of ram.. imagine being able to say that today. most people would be like 'wtf is that?'


one last thing.. how old are you people?! i took a class on this last semester.. and we worked with p4 architecture. i've never even heard of the hc6811...

 

[Runamile]

Originally posted by: gamer4life
In a microprocessor class I took in college, we were working with the Motorola HC6811.
This had 16 address lines and 8 data lines. (i.e. 16 bit processor)

Does the AMD64 have 64 address lines and 32 data lines?

The 68HC11 has 40 data lines, or 5, 8-bit parallel ports. Is that what you are refering to as data lines? I am doing some coding in C for one of these babys for a computer mod job right now, so I have been digging all through the specs. It is a great chip BTW, if not a little old. Very competent though.

Originally posted by: itachi
one last thing.. how old are you people?! i took a class on this last semester.. and we worked with p4 architecture. i've never even heard of the hc6811...

The 68HC11 is an embeded microcontroller that has been around for several years. There is quite a large following behind it. I have head that many college students have learned on these things. As for as us old people go, I'm a sophmore in college and I'm using this chip. But I do admit I learned about it while looking through some schematics while debugging the code to a 5 year old instrument which was controlled by this thing.

 

[gamer4life]

Originally posted by: Runamile
The 68HC11 has 40 data lines, or 5, 8-bit parallel ports. Is that what you are refering to as data lines?

No, I was referring to the data bus. There are only 8 data lines coming out of the 6811.

You are referring to addressable output ports. I think you can have more than just 5. Depends how many address lines you use to address them.


I'm 27, I took the class in 2000. I think they were changing to the Motorola 6812 the next semester.
We had to buy an EVBU with this processor on it and we had a lab every week. We wrote programs, sent them to our boards through the serial rs-232 port and used the onboard capabilities like a/d, d/a, input capture, interrupts, etc.