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PowerPC G4 Plus taped out

Long-awaited chip done and dusted, apparently

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Updated Register sources have added their voice to earlier hints that Motorola has completed the PowerPC G4 Plus, a process known in the trade as 'taping out'.

Some weeks back, we came across rumours from Motorola that the chip, the successor the desktop-oriented PowerPC 7400 (aka the G4), has finally begun sampling.

Now, sources close to Apple tell us that the G4 Plus has taped out and that the Mac maker received initial silicon just a few weeks ago.

That timeframe has since been confirmed by a Motorola source cited by MacCentral.

Of course, while the chip may be feature complete and fully operational, Motorola will now have to work on producing good, marketable yields, so don't expect a G4 Plus-powered Mac just yet. Apple itself will have to test the chip and verify that it operates with its current hardware - if not, motherboards will have to be modified accordingly.

MacCentral's own mole showed Motorola's new-found conservatism when he finally admitted that Apple would be able to ship product based on the chip by "mid-summer" 2001. Given the problems Motorola had getting the yields right on the PPC 7400, which is still stuck at 500MHz, and the trouble it got into with Apple - remember Apple's damning complaint against the chipmaker in its autumn 1999 fiscal statement? - it's not surprising Motorola is playing it cautious.

That said, since Apple seems keen on launching product before chip supply is there - as per the original Power Mac G4 launch - we reckon we could see a G4 Plus-based Mac launched sooner than that, possibly around May's Worldwide Developers Conference.

Either way, it's a good bet that Power Macs driven by the G4 Plus will be showcased at next summer's MacWorld Expo in New York - probably as successor to the dual-7400 G4s.

The timing of today's revelation certainly ties in with Motorola's own plan to unveil the chip in a couple of weeks' time, at chip industry shindig the Microprocessor Forum, to be held in San Jose, California.

Our sources were unable too offer any solid details on the G4 Plus as it stands today. We expect at least a 700MHz clock speed, as mentioned at last year's announcement, and will include a redesigned instruction pipeline (to allow it to reach such high clock speeds without hitting its processing efficiency), three extra AltiVec engines and two more integer units.

Indeed, MacCentral's Motorola insider told the Apple-watching Web site that the G4 Plus - apparently the official nomenclature for the product - will debut at 750MHz.

The chip's L2 cache will be brought onto the die, to allow CPU and cache to communicate at the same speed. The L2 connects to the L1 across a new, 256-bit bus. The 'G4 Plus' will support external, backside configuration L3 cache, up to 2MB of it.

On Tuesday, Motorola unveiled a version of the regular 7400, called the PowerPC 7410, aimed at the embedded market. The 7410 is fabbed at 0.18 micron, making for a smaller, cooler chip. Available clock speeds, like the 7400, are 400, 450 and 500MHz, with a 550MHz version promised soon. ®

Related Link

MacCentral's PowerPC G4 Plus story

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