Ask the Doctors: ExpressCard and UAD-Xpander Demystified
By Mike Barnes

This month's "Ask the Doctors" answers your questions about the new UAD-Xpander for laptops. It looks like the ideal mobile mixing rig, but what is ExpressCard, and how does it work?

1. What is ExpressCard and who developed it?
ExpressCard is the third-generation interconnect standard developed by PCMCIA (Personal Computer Memory Card International Association) and follows the first-generation PC Card and second-generation Cardbus formats. The PCMCIA was founded in 1989 as an industry trade association and standards body to develop, maintain and promote an interchangeable modular card standard for portable computers.

The ExpressCard specification was released in September 2003 and leverages the scalable, high-bandwidth serial PCI Express and USB 2.0 interfaces. ExpressCard replaces conventional parallel buses for I/O and allows developers to create modules using either USB 2.0 or PCI Express for their highest-performance applications such as audio DSP!

UA uses PCI Express via the UAD-XpressCard for optimum high-bandwidth data transfer between the laptop to the UAD-Xpander chassis, which houses the proprietary DSP vector processor that runs UA's Powered Plug-Ins. UA is the first audio manufacturer in the world to offer an ExpressCard solution.

ExpressCard/34 card

2. Is ExpressCard backward-compatible with Cardbus equipped laptops?
The ExpressCard connector uses a new interconnect (26-pin) and bus (PCI Express/USB 2.0), and its form factor is up to 40 percent smaller than a PC Card so cannot be used in a standard PC Card or Cardbus laptop.

CardBus vs. ExpressCard Sizes

3. Performance Comparison and Physical Specifications of ExpressCard
Add-in cards of this new class of are known as ExpressCard modules and come in two physical formats: ExpressCard/34 and ExpressCard/54. The numerical suffix denotes the width of the card in millimeters. ExpressCard/34 modules can fit into either an ExpressCard/34 slot or an ExpressCard/54 slot. ExpressCard/54 modules can only fit into an ExpressCard/54 slot. UA chose the ExpressCard/34 module specifically to support the widest range of laptops. For example, the Apple MacBook Pro only supports ExpressCard/34.

Each ExpressCard slot supports a single PCI Express lane (x1) operating at the baseline 2.5 Gbps data rate in each direction.

ExpressCard vs. CardBus Technology

PCI Express (x16)	4,000 (8,000 full-duplex) MB/s
ExpressCard (x1)	250 (500 full-duplex) MB/s
Cardbus/PCI (32-bit/33Mhz)	132 MB/s
Gigabit Ethernet	125 MB/s
FireWire 800 (1394)	80 MB/s
USB 2.0	48 MB/s (480 Mbps)
FireWire 400 (1394)	40 MB/s
PC Card (16-bit)	20 MB/s
USB 1.1	1.2 MB/s (1.5 Mbps & 12 Mbps)
MAXIMUM TRANSFER RATE - BUS COMPARISON TABLE (maximum serial data Byte rates are 1/10th the bit rates because of additional bits used for encoding)

4. How many laptops have ExpressCard, and why use this instead of 1394/FireWire?
According to IDC Research, the ExpressCard penetration rate in notebooks for 2006 numbered 16.7 percent. IDC estimates that ExpressCards will continue to see growth in 2007, with numbers expected to reach the 31.4 percent mark. Also IDC forecasts notebook units growing at more than 25 percent over the past three years (vs. desktops at ~10 percent) and expected to grow at 20 to 25 percent in 2006 (vs. desktop at 5 percent); notebook shipments are expected to exceed desktops in several mature markets (U.S., Western Europe) by late 2007 or early 2008.

ExpressCard is featured on nine of the top ten laptops in the Notebookreview.com click-through rankings, and major laptop vendors such as HP now feature ExpressCard at all price points across their entire notebook line.

ExpressCard is expected to be the de facto standard adopted for high-bandwidth notebook peripherals, including digital TV. Notebook Review magazine provides a list of ExpressCard equipped PC notebooks. Manufacturers already shipping include Apple, Dell, Fujitsu, HP, Lenovo, LG, NEC, Sony and Toshiba.

Apple includes a single Expresscard/34 slot on all the MacBook Pro line of products but not on the cheaper MacBook. PC Notebooks often include a legacy cardbus slot.

	A: ExpressCard slot. B: ExpressCard 26-position connector. C: PC card slot. D: PC card 68-pin connector. E: Ejector buttons F: ExpressCard Guidance feature
Typical Stacked ExpressCard/PC Card Host Slot

ExpressCard Vs. FireWire: Why UA Chose ExpressCard

1. Bandwidth. ExpressCard offers up to 2.5 Gbps of dedicated bandwidth today, which is more than six times the bandwidth offered in the standard FireWire configuration. The PCI-SIG have already announced plans to improve still further. ExpressCard is the optimum solution for processing large numbers of tracks at high sample rates and low buffer sizes, and provides headroom for the future. DAW hard drives and I/O DSP processors are already pushing the limits of FireWire.  Using ExpressCard for you outboard DSP processing frees up more bandwidth for other FireWire devices.
2. Unified Driver. Because ExpressCard leverages existing PCI-Express technology, a single unified UAD driver can be developed for PCI/PCI-X/PCIe and ExpressCard systems, and allows seamless expansion of up to four UAD cards in any arbitrary UAD combination.
3. Standardization. PCIe is the new bus standard for desktops, and ExpressCard is the direct equivalent on laptops. Major chip manufacturers and computer vendors are aggressively driving the initiative.
4. Cross-Platform. Industry-standardized interface on both Mac and PC Notebooks. Premium models of all major manufacturer laptops have already adopted ExpressCard.
5. Practicality. Laptop users can dedicate USB2 or FireWire for audio I/O or hard drives and ExpressCard for audio DSP. Because many musicians are already using a shared FireWire bus for Audio Interfaces or recording hard drives, the available leftover FW bandwidth and latency for DSP is unpredictable.

5. What is inside the chassis? Is the Xpander more or less powerful than a regular UAD-1 or UAD-1e?
The UAD-Xpander uses the PCI-Express bus via ExpressCard, and therefore the Xpander uses a derivative of the UAD-1e card internally with exactly the same DSP power as the other UAD family members.

The chassis is also what we call Alumi-Cool: solid aluminum (no plastic here), self-cooling, noiseless and fanless.

In order to keep the cost to our users as reasonable as possible, the UAD-Xpander is designed specifically for UAD use and is not a general-purpose PCI-e Expansion Chassis, which would have other power, cooling, and noise issues.

6. What is this UAD-Link cable that the UAD-Xpander uses, and can I use it to add multiple Xpanders?
The UAD-Link cable uses the same physical form factor and impedance as HDMI cables, but it is used for higher-speed 2.5Gbps PCI Express data transfer. UA-approved UAD-Link cables must be used to guarantee data integrity and will be available at my.uaudio.com. The UAD-Xpander will ship with a 1 to 1.5m cable, and UA is in the process of qualifying longer 3 to 5m cables.

The UAD-Xpander is designed as a single mobile DSP solution for laptops and cannot currently be chained with other UAD-Xpanders. If your laptop has two ExpressCard/34 slots, you can use two UAD-Xpanders in exactly the same way as multiple UAD cards.

7. Why couldn't you power the Xpander from the ExpressCard slot or FireWire bus?
Expresscard only has limited power available: 1.3W for ExpressCard/34 modules and 2.1W for ExpressCard/54. The UAD-Xpander requires around 10W of power.

FireWire is not as ubiquitous in the PC laptop world as in the Mac laptop world and is generally unable to provide any power for the needs of the UAD-Xpander. While FireWire theoretically offers the option of bus-power of 40V at 1.5 amps according to the IEEE 1394 specification, this has been implemented in a discretionary fashion by the majority of laptop vendors in an effort to manage/conserve power. Therefore, the actual power available via FireWire-equipped laptops varies widely. Apple, which invented FireWire, only provides 9 to 12.6V at 0.9 amps for all Firewire devices on the new Mac Book Pro and recommends using this power source only for products designed to use less than 7W of maximum sustainable power. FireWire power is also variable, depending on whether the laptop is powered by AC or battery!

For Example: 17-inch MacBook Pro Computer (October 2006) FireWire power is present any time the AC adaptor is powering the system, including shutdown. On battery power, FireWire power is present only during system run and is unpowered during sleep and shutdown to prevent unintentional battery drain. Both of the FireWire connectors provide unregulated 9 to 12.6V at 0.9 amps maximum (fused). Developers should design to <7W maximum sustainable power. Output voltage follows the system's battery power, such that voltage is dependent on the state of the battery's charge, as listed below. When the system is receiving AC power, with either a fully charged battery present or no battery present, output voltage is nominally 12.6V. FireWire power is on in run, sleep, or shutdown. When the system is receiving AC power, and the battery is charging, output voltage will follow the battery voltage (unregulated 9V to 12.6V). FireWire power is on in run, sleep, or shutdown. When the system is not receiving AC power, the output voltage follows the battery voltage (unregulated 9V to 12.6V), and only when the system is running. FireWire power is turned off in system sleep or shutdown when no AC power is present (see Apple Developer notes: FireWire Product-Specific Details).

8. Can I connect a UAD-Xpander via ExpressCard to a desktop PC/Mac so I can use the UAD-Xpander on my desktop, and will it work with other UAD cards?
Yes. UA will offer an optional, approved "UAD-Xtenda," a PCIe to ExpressCard adapter card and an approved 3m UAD Link cable so that users can switch between laptop and desktop. This requires a Mac or PC running OS X/Windows XP/x64 or Vista and an open PCI Express slot (not compatible with PCI or PCI-X slots).

PCIe ExpressCard adapter for desktop computers

UA will provide more details on use of ExpressCard compatibility and use of the UAD-Xpander in desktop systems in the future.

9. What is a PCIe Cable?
The PCI-SIG is in the process of specifying a single cable and protocol for distributed systems which will allow PCI Express to be transmitted up to 10M over a single cable. This would allow future PC systems to blur the distinction between laptop and desktop form factors, where functionality can be distributed. (For example, there is a graphics engine in the monitor, or audio I/O and DSP in an external device). Though it's unlikely to see commercial introduction until 2008, this is another reason UA has backed the single PCIe driver approach; it will allow UA to rapidly ship PCIe cable products when it becomes widespread.

Because no formally approved PCIe Cables exist yet, UA is adopting the concept but transmitting PCIe using our own UAD Link cables.

10. When will UA begin releasing ExpressCard-based UAD products?
UA has been in development on this laptop UAD solution for a significant period of time and is showing working prototypes of the UAD-Xpander/XpressCard at NAMM 2007. We expect to ship the final UAD Xpanders at the end of Q1 2007.

Article References & More information on ExpressCard

http://www.expresscard.org

http://www.pcmcia.org

http://www.pcisig.com

http://laptopmag.com/Features/Instant-Expert-ExpressCard.htm

http://www.dell.com/content/topics/global.aspx/vectors/en/2003_expresscard?c=us&l=en&s=corp

http://en.wikipedia.org/wiki/ExpressCard

http://www.1394ta.org

http://www.usb.org/developers/docs/

Questions or comments on this article?