Updated Apple inadvertently revealed its hand last night, posting - albeit briefly - specs. for upcoming Power Macs on its online AppleStore.

The new desktops will indeed be branded 'G5'.

A graphic on the Power Mac G4 page detailing that computer's current spec. was swapped with the equivalent image. The image was presumably being prepared for Monday, when CEO Steve Jobs is expected to announce new machines at the company's annual Worldwide Developers Conference.

The mistake was soon spotted and the original re-instated, but not before it had been seen by numerous Mac fans, at least one of whom managed to take a screenshot, posted on MacMinute.

Update #2 The site has now pulled the images at the request of Apple's lawyers. So too has MacRumours.com. Think Secret is still showing them here.

According to the screenshot, the new desktops will sport 1.6GHz, 1.8GHz and 2GHz "PowerPC G5" processors, running across a 1GHz system bus, which pretty much confirms the G5 as IBM's 64-bit PowerPC 970. The Macs will offer up to 8GB of DDR SDRAM, and feature Serial ATA hard drives. AGP 8x Pro graphics cards will drive the machines' displays. Expansion will be provided by three "PCI or PCI-X" slots, and - for the first time on a Mac - USB 2.0 ports, of which there are three. The boxes contain a single Firewire 800 port and two Firewire 400 connectors. In addition to the expected AirPort Extreme readiness, integrated Bluetooth and audio in/out, the desktops feature optical digital audio I/O, presumably an S/P DIF port.

At the 970's launch last October, IBM said the chip would ship at up to 1.8GHz and feature a system bus running at up to 900MHz (for up to 6.5GBps of "useable" bandwidth"). Apple's specs. suggest either IBM has bested it performance targets or the Mac maker is overclocking the chip.

The other specs. are interesting in that they closely match what you'd expect from a top-end Windows PC these days: AGP 8x, Serial ATA, USB 2.0 and S/P DIF. Apple has traditionally lagged behind the PC world in offering the latest bus speeds, memory formats, hard drive connectors and so on. Despite being an early proponent of USB, Apple has never offered the latest generation of the bus, USB 2.0, until now.

That suggests not only is Apple being forced to modify its blasé attitude to Mac buyers thanks to the economic climate, but that the company may be using an off-the-shelf PC chipset. The Power Mac G5s are expected to feature a HyperTransport-based bus, so it's possible Apple is using HT-enabled chipsets from a third-party rather than design its own.

WWDC kicks off on Monday with Jobs' 10am keynote - 1pm in New York, 6pm in the UK and 7pm in the rest of Europe. The speech is being broadcast on satellite, and wired to most of Apple's US stores, not to mention a press event in Germany for local media.

Jobs will certainly discuss Panther, the next major release of Mac OS X, probably version 10.3. Apple has said as much, but it's what else he'll pull out of his stage magician's top hat that has the Mac world collectively holding its breath. The venue, and the satellite broadcast to AppleStores and elsewhere - these are, after all, not the kind of things that you usually associate with a show for programmers.

What users want to hear is an announcement of next-generation Power Macs based on IBM's 64-bit PowerPC 970 processor. Apple's graphical glitch would seem to confirm that's exactly what he will reveal.

IBM's original shipment schedule for the 970 timetabled samples of the chip to arrive during Q2 2003 and full production to begin during the second half of the year. It's possible that IBM has begun to ramp up production rapidly, but if it has it's a very fast ramp indeed, faster than is usually the case. Motorola's successor to the G4-class PowerPC 7455, the 7457, began sampling last March but it's not expected to enter volume production until Q4. IBM may have a more aggressive ramp than its PowerPC partner, but the indications are that not all the new G5 boxes will ship next week and supply may be constrained for a month or so.

One question remains: will he announce new PowerBooks too? Mac rumour site MacWhispers has flown the flag for new PowerBooks based on the 970. Certainly Apple is believed to have new 15.4in PowerBooks in the works - as we reported here, it is believed they'll manufactured by Taiwanese notebook producer Compal. A source there said the machines would be produced in the second half of the year, which could mean they'll ship in just over a week's time - but could equally point to an much later slot. In MacWhisper's favour is the fact that the current 15.2in PowerBook was recently discounted, has a broadly lesser spec. than the other PowerBook models, and is now long in the tooth.

But that doesn't mean it will contain a 970 - indeed, what little we know of the 970's power characteristics suggests that's unlikely. As is the fact that Apple traditionally brings new CPUs to the desktop first, and notebooks later, often simply because of the extra engineering needed to cope with new chips' heat dissipation characteristics.

Earlier this year, rumours surfaced about dual-processor PowerBooks, a logical next step after the launch of the 17in display. While dual-CPU PowerBooks haven't been explicitly linked to WWDC, they have to remain as possibility.

Update #1 Something seems to be happening on the PowerBook front, at any rate. One reseller was told this week that his order for a number of 15in PowerBooks was cancelled by Apple, notification of which was appended with a comment that he should wait until Monday... ®