Will The First Thunderbolt Peripheral Be The iMac?

Apple and Intel introduced the impressive new Thunderbolt interconnect last month on the MacBook Pro line, but folks like me who bought one have nothing to connect to yet. It was exciting to see the wide variety of Thunderbolt peripherals on display at the NAB show in Las Vegas last week, but none of these will ship to end-users before the middle of the summer. But evidence is mounting that Apple will be the first out of the gate with a Thunderbolt peripheral, it just won’t be the sort of peripheral you might expect. I am hearing rumors that the new iMac, to be introduced this month, will be both a Thunderbolt host and peripheral in one! Read on for what this means in the real world.

A Quick Review of Thunderbolt

Before we dive into this discussion, it is probably wise to revisit the latest information about the Thunderbolt interconnect. Although Thunderbolt MacBook Pros are widely available and Intel, Apple, and others have been talking about the technology quite a bit lately, there is still much confusion about just what this new interconnect is all about.

Put simply, Thunderbolt passes two important protocols between a computer and its peripherals:

1. Video, in the form of a full DisplayPort signal
2. Data, in the form of two full-duplex 10 Gb PCI Express lanes

These two signals are multiplexed onto a Mini DisplayPort interface. Although envisioned as an optical interconnect, Thunderbolt is today an electrical interface that uses copper wiring.

The Shape of Things To Come

There is one key reason to be excited about Thunderbolt: This high-bandwidth connection promises to change the physical shape of computers, since external devices can be accessed with the same performance as internal devices. In fact, design engineers who have worked with Intel’s initial chips report that integrating existing PCI Express peripherals with Thunderbolt is a piece of cake: The chips don’t know that they are located outside a computer!

Historically, laptops have been severely limited when it comes to I/O bandwidth. One reason for the lackluster performance of most portable computers is that they are strangled by slow interfaces like USB, FireWire, and ExpressCard. But Thunderbolt changes everything.

My new MacBook Pro has far more I/O capability than the iMac sitting on my desk, and perhaps even more than the Sandy Bridge desktop system I built for my lab! Packing all this I/O bandwidth into a single cable connection allows us to do magical things: We can put a wide variety of peripherals, from displays to storage networking, on that one little port and everything can operate at full speed.

This changes the very shape of the computer. No longer do we need to reserve empty space inside the box for full speed peripherals. Instead, a compact machine like a laptop or an iMac can connect to external devices without sacrificing performance. The next-generation Mac Mini might even be stackable, with a variety of expansion bases produced by third parties.

The iMac as a Peripheral

But things get weirder and more wonderful if we consider that the PCI Express lanes found on a Thunderbolt connector can even extend one computer’s resources to another. It is already possible for a MacBook Pro or other DisplayPort-enabled device to use the iMac as a monitor. Yet this leaves the keyboard, hard disk drive, camera, and other peripherals idle.

But what if we could use every part of the iMac as an extension of the MacBook Pro or vice versa? Plugging a Thunderbolt-equipped MacBook Pro into a new Thunderbolt iMac could allow the desktop system to take on the personality of the laptop entirely, sharing all peripherals and connections transparently and at full speed. The running operating system would instantly see the iSight camera, keyboard and mouse, network expansion ports, and of course the display panel.

But let’s take things a step further: What if the MacBook Pro and iMac shared their CPUs and graphics adapters as well? Grand Central Dispatch, built into Snow Leopard, could use these to accelerate rendering or gaming, using the high-speed PCI Express interconnect to share all the resources of both machines as a single compound computer.

Stephen’s Stance

Who doesn’t want an eight-core MacBook Pro with a 27-inch high-resolution display? Who wants the hassle of synchronizing documents and files between a desktop and portable computer? Why not just merge everything into a single computer over the high-speed Thunderbolt interface?

There is no reason this cannot be done, and I have heard many hints and suggestions that this is exactly what Apple is planning to introduce next week. The supply of iMacs is running short, and no one doubts that Thunderbolt will make an appearance on the replacement device. The only question is whether Apple will allow this kind of host to host interconnect, and how integrated it will be.

Jan TÃ¥ngring consulted electronic experts and found this to be a credible idea at least. Read in Swedish (English translation)