Speed of processors, does it have a max?

  • #26
Baluncore
Science Advisor
9,453
3,924
That assumes that clock and date lines have the same length.
Or that the clock path be very slightly longer in propagation time than any of the data lines.
We need a delay. Can you just run a wire around the inside of the case?
When a parallel bus was run on a mainframe backpanel, several identical twisted pairs with the same length were used to route the differential signals. Once terminated with wire wrap, the excess length was folded into the gaps between the connector blocks. To modify the back plane required access, carefully unfolding and lifting out the delay lines.
 
  • #27
1,905
1,237
Can you just run a wire around the inside of the case?
Good old tech.

Knowing the size of a motherboard this makes it all too clear how valuable it is to have cache memory located physically on the processor die.
Actually, for this the distance induced delay is not the main player. The structures on the CPU are really small: you can drive them with small effort - you can drive them really fast. But once you are 'outside', you have more capacitance to fill up and more inductivity to stand in the way: the requirements are stricter and so the speed becomes limited.
 
  • #28
Svein
Science Advisor
Insights Author
2,176
711
If I haven't errored the order of magnitude, it looks like light travels 30 cm in one nanosecond,
In vacuum, that is correct. On a PCB the speed is closer to 20cm/ns.
We need a delay. Can you just run a wire around the inside of the case?
If you have a relatively new PC motherboard, try to get a glimpse of the traces from the CPU / North bridge to the DRAM. You will see that some of the traces are wiggly - that is due to the fact that they would otherwise be too short relative to the longest traces.
 
  • #29
52
29
Actually, for this the distance induced delay is not the main player. The structures on the CPU are really small: you can drive them with small effort - you can drive them really fast. But once you are 'outside', you have more capacitance to fill up and more inductivity to stand in the way: the requirements are stricter and so the speed becomes limited.

Interesting. Can you recommend me material to read on this?
 
Last edited:

Related Threads on Speed of processors, does it have a max?

  • Last Post
Replies
5
Views
4K
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
1
Views
3K
  • Last Post
2
Replies
26
Views
4K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
17
Views
6K
Replies
5
Views
42K
  • Last Post
Replies
12
Views
2K
  • Last Post
Replies
4
Views
2K
Top