Feeds

New G4 roadmaps promise Apple harvest

RapidIO, revved bus options for iMac2

  • alert
  • submit to reddit

Internet Security Threat Report 2014

Exclusive While Apple watchers look for first sightings of the G5 chip, Motorola is taking the G4 into fertile territory.

By this time next year three as yet unannounced versions of the G4 will dramatically boost internal bandwidth, support switched fabric interconnects, and will see the processor talk to memory at full bus speed, according to disclosures from Motorola sources.

One caveat: as far as we know Apple hasn't committed to adopt these new G4 variants. Now it's got a portable operating system it can choose something really weird and exotic if it desires; but common sense and recent precedent suggest that these two processors will form the mainstay of Apple’s iMac2 and low-end professional lines.

According to Motorola sources, a tweaked version of the Apollo 7450 G4, the 7470, will be ready for volume production shortly after the end of Q2, in time for a summer ramp. The 7470 will be manufactured on a 0.13 micron process, allowing for a smaller die size with room for 512K of L2 cache, and support up to 4MB of DDR-SDRAM L3 cache.

The 7470 supports a modified bus protocol, MPX+, which supports double data transfer and which should effectively run at 266Mhz according to sources.

The MPX+ bus retains MPX's 36-bit addressing lines, and is described as an interim measure. Don't expect dramatic leaps in SMP scaling - two will remain the sweet spot. The 7470 should scale to 1.5GHz. In parallel development, Motorola is priming a cut-down 7470, labelled the 7460, which doesn't support L3 cache.

But the third addition to the G4 family, the 7500 - slated for volume production by this time next year, should steal some headlines. Like the 7470, the 7500 will be built to a 0.13 micron process, and will feature a 14 stage pipeline (11 integer).

Having boasted one of the shortest (and most efficient) pipelines in the business, with the G4's original four-stage unit, Motorola has been increasing the pipeline depth, which allows it to deploy higher clock frequencies. There's a whole science to optimizing processors to minimize the branch jump table penalty. This shouldn't detain us for too long but a crude summary is that a deep pipeline allows the processor to second guess the subsequent instructions, at the cost of clearing the pipeline when it gets the wrong answer. If a processor has a higher clock frequency, it can clear the pipeline quicker when a mis-prediction is flagged.

More noteworthy is that the 7500 will be the first desktop processor to employ the RapidIO architecture to communicate with the system at 500Mhz.

RapidIO is a switched fabric interconnect which mirrors the parallel Infiniband initiative: the former is endorsed by the embedded industry, the latter by big iron system vendors, so the two don't really overlap. But the move to a standard switch architecture away has been a long time coming: high-end systems use their own proprietary switches (in mainframe terminology, a "crossbar switch") or a combination of a bus and a switch.

In practical terms it will permit the the memory controller to be housed on the die, communicating at full clock speed. So potentially, there's no need for L3 on-die cache. With DDR-SDRAM at 266Mhz and heading for 333Mhz, this should result in a comfortable improvement in throughput.

Our source suggests that Apple will have "little choice" but to adopt RapidIO, given that the bulk of Motorola and IBM PPC volume is in the embedded business. But there's much to be gained too, as RapidIO becomes the internal wiring for knitting together the various bus protocols a desktop PC needs to support: ATA, USB, FireWire and so on.

With Intel's latest Northwood systems employing a 400Mhz front side bus (up to 533Mhz by the end of the year), Apple loyalists should take some cheer from these developments. System performance owes a great deal to the internal bandwidth, and running a high frequency processor on a slow frequency bus has never been considered optimal.

More importantly for Apple, it allows the company plenty of potential for system improvements to the consumer iMac range, and far more scope for differentiating between the pro and consumer lines. Right now, they look awfully similar. ®

Internet Security Threat Report 2014

More from The Register

next story
Facebook pays INFINITELY MORE UK corp tax than in 2012
Thanks for the £3k, Zuck. Doh! you're IN CREDIT. Guess not
Google Glassholes are UNDATEABLE – HP exec
You need an emotional connection, says touchy-feely MD... We can do that
Lawyers mobilise angry mob against Apple over alleged 2011 Macbook Pro crapness
We suffered 'random bouts of graphical distortion' - fanbois
Just don't blame Bono! Apple iTunes music sales PLUMMET
Cupertino revenue hit by cheapo downloads, says report
US court SHUTS DOWN 'scammers posing as Microsoft, Facebook support staff'
Netizens allegedly duped into paying for bogus tech advice
Feds seek potential 'second Snowden' gov doc leaker – report
Hang on, Ed wasn't here when we compiled THIS document
Verizon bankrolls tech news site, bans tech's biggest stories
No agenda here. Just don't ever mention Net neutrality or spying, ok?
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Simplify SSL certificate management across the enterprise
Simple steps to take control of SSL across the enterprise, and recommendations for a management platform for full visibility and single-point of control for these Certificates.