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Mix Magazine

This installment of The Bitstream column appeared in the September 2001 issue of Mix Magazine.

The Bitstream

This column discusses the emerging iSCSI and Serial ATA standards…

Alas, Poor SCSI, I Knew Him Well

A change of season is upon us, with the smell of frying power supplies in the air…It’s Autumn across the US, the twilight of Summer, all slanting light and cold winds. It may be the twilight too for the SCSI standard, having just celebrated it’s 20th anniversary with a wee shindig down in San Jose. SCSI better watch out as the young Turks are out to usurp it’s crown.

You may think I’m bonkers but, the SCSI Trade Association really did have a birthday party for the standard that has soldiered on longer than any of it’s architects had imagined. For performance storage peripherals, it’s still the attach method of choice, with the installed base dwarfing it’s only competition, Fibre Channel. For high performance in a multi–user environment like sound–for–picture, Fibre Channel is the way to go. Granted, most SANs continue to use SCSI–attached drives behind a FC façade. But, native FC devices are working their way into the marketplace though I feel they’ll never achieve the level of penetration that SCSI has enjoyed. That’s because there just aren’t that many installations that require the high performance and availability that Fibre Channel affords. Desktop hardware will continue to dominate the number of storage devices shipped for quite some time, But, there’s an emerging trend that will not only impact us but will also turn the storage industry on it’s head and that’s home servers.

I should be more general and say storage for information appliances, but hey, the concept is this: in short order, DTV, P2P, DVD2, FTTH (Fiber To The Home) and other technologies will converge on Jane C. Consumer (the “C” is for Conspicuous), forcing her to purchase the latest and greatest gadget. That home electronics trifle will most definitely contain rotating storage, at least until some serious manufacturing hurdles are overcome, and the cheapest rotating storage is still magnetic. Home servers, STBs (Set–Top Boxes) and personal video recorders all require big storage but it’s got to be cheap…and SCSI ain’t cheap. Now ATA, that’s cheap.

Er, sorry, not cheap but cost effective. Though Intel has made a lot of noise in the hope of establishiing their USB spec (Unused Serial Bus) as the de facto standard for external peripheral attachment, those in the know tend to dismiss USB as a great way to hook up brain dead devices but, please, nothing that requires serious negotiations with either host or peer. SATA or Serial ATA is another matter. Unlike USB, SATA is designed for inside the box, not outside where Jane C. can muck about with it. Along with InfiniBand, another fundamentally radical internal technology, SATA will change the look, feel and performance of new computers.

Wicked competition in both the consumer appliance and desktop computing space dictates that manufacturing cost be trimmed to the bone. Intel has proposed SATA as the nexgen storage attach protocol that promises to finally give SCSI stiff competition for manufacturer’s dollars. Here’s the spin on SATA from Intel’s Developer Forum, “This technology…will enable smaller, sleeker PC designs by replacing today’s bulky ribbons…with very thin cables that can quickly transfer large amounts of information. The cables and connectors…will replace today’s products based on the Parallel ATA storage interface. Serial ATA will enable future growth and stability of computers while maintaining compatibility with today’s software base.”

Along with Intel, the specification working group includes IBM, Dell, Maxtor/Quantum, Seagate and APT Technologies, an engineering company. Version 1.0 of the spec, dubbed Ultra SATA/1500, was released in November 2000. “So, what,” you ask, “is so cool about SATA?” Well, Bucko, it’s that “S” as in Serial. Take a parallel communications bus over a fat ribbon of conductors and serialize it by time domain multiplexing. This converts that w–i–d–e ribbon hooked in a finicky physical serial configuration to just a single conductor plus shield capable of star configurations. That in itself is nothing too rad but it does allow computer manufacturers to reduce the total internal volume while boosting the data throughput to 1.5 Gbps to start. Double and quad speed versions are scheduled to follow roll out of the first Ultra SATA/1500 products next year.

To me, Serial ATA means slim, attractive technology advancement. To you, it’ll just be a good thing.

Pedant In A Box

Buzz words for this month are…


Advanced Technology Attachment: This is the name that ANSI, the American National Standards Institute, gave to the specification covering IDE or Integrated Drive Electronics. IDE is an attachment interface used between motherboard and disk. IDE is, in turn, based on the IBM PC’s Industry Standard Architecture or ISA, a 16 bit bus standard. There is also an enhanced version of IDE called EIDE. EIDE includes, along with support for DMA (Direct Memory Access) and non–disk devices like CD and tape, a 28 bit Logical Block Address (LBA) to specify the actual cylinder, head, and sector location of data on the disk. The 28 bits provide an address space up to 8.4 GB in size, hence the 9 GB ATA drives typically seen in most mass market computers.


Despite what Digidesign’s marketing department would like you to think, Time Domain Multiplexing is one “channel coding” method for delivery of multibit data over a serial transmission channel. Numark’s ADAT “Lightpipe” and the AES Type II “S/PDIF” optical interfaces are two common examples of inherently parallel data (AES/EBU linear PCM) being channel coded or repackaged for serial transmission over a single, consumer–grade POF or Plastic Optical Fiber.


OMas welcomes back our one month of “Summer” to The Pueblo By The Bay. Long may warm weather live…This column was created while under the influence of Love Tractor’s (they’re baaaack…) theskyatnight and Joe Satriani’s Engines Of Creation.