LAPTOPS, DESKTOPS, PCIe3.0 and Cables:
One thing really overlooked is the fact that the bandwidth requirements in many cases will
DECREASE. Here's what I mean:
If we have a "Graphics Box" for a laptop which contains only a Graphics card then replacing that
portion of the motherboard PCIe bus with an extension cable makes sense. However, I believe that
the APU (CPU + GPU) will be the processing element of choice for laptops. The main reason for
this, as any gamer knows, is the issue of bottlenecking the CPU. The CPU in modern laptops has
little room for a heatsink which limits its processing capability (and laptops are getting thinner). A computer is either bottlenecked by the CPU or the GPU so an efficient laptop is limited in how powerful the graphics option will be. So if you want a lot of processing power in the form of an add-on BOX it's simply best to avoid any bottlenecking issues and heat issues and build all processing into the external box.
Since the CPU portion (as an APU) is now moved externally we should have a second set of RAM to
be used with the CPU. It need not be the full System Memory, just a portion of it.
Removing the computer (desktop or laptop) as a source of major bottlenecks by moving all the important processing and memory components to an external box removes all the confusion surrounding bottlenecks. A consumer can simply pick up the BOX which fits his budget and needs then plugs it in! A great benefit to the laptop in not using its onboard CPU for major processing is the reduction of noise. Small, high-speed CPU fans are very annoying. An external BOX, on the other hand, would be comprised likely of two large heatsinks (both sides) and a large slow-moving fan.
Laptop Gaming Scenario:
A highly efficient, low-power business laptop is hooked up to an external BOX (via the PCIe
cable). The box is already hooked up to a desktop monitor. The laptop is passing through its
video data (the external BOX need not be on for this).
Now the BOX is turned on and a game is loaded:
1) the game, "Crysis 4" is copied from the hard drive to the RAM in the BOX (not the laptop)
directly via the PCIe cable.
2) the BOX's APU provides the processing. *NOTE: it may make sense to have a single Memory Unit
comprised of the VRAM + RAM2.
3) the BOX sends the image to the monitor
Analysis:
We used the PCIe cable only for copying the hard drive game data. Even with an SSD we could have
easily done this with USB3. So why don't we have "APU boxes" for laptop gaming via USB3
connections?
DESKTOP:
The real bottleneck in the desktop dealing with the PCIe bus is communicating between the CPU and
Graphics cards. The demand for PCIe bandwidth obviously increases with faster graphics cards and
CPU's but it IS reduced in the following scenarios:
a) as Graphics Cards assume more of the processing this lessens the CPU->GPU burden as this
happens AFTER the PCIe bus.
b) APU's will probably replace the normal CPU + Graphics card scenario. In a video game scenario,
the main CPU could be used simply to send the data in the System RAM to the APU's to be
processed. It's difficult to say if this scenario works however, because now we have the PCIe bus
in place of the high-speed CPU-SYSTEM MEMORY interface.
It's most likely that the optimal solution would be to have a system augmented with an APU
Graphics card but with some of the processing still done by the CPU.
Summary:
- We could build an external processing box comprised of an APU+RAM today using only USB3 for
laptops and desktops
- APU augmented desktop graphics cards may be ideal for obtaining the maximum processing power
(before bottlenecking the PCIe bus) in a desktop
(NOTE: I've only touched on certain aspects of PCIe and the use of the cable. I'm certainly not saying we don't need increased bandwidth; I'm merely commenting that in certain scenarios we don't need that bandwidth as much as in other scenarios.)