Intel tweaks P4 core voltage
Making room for shift to 1.7GHz? Will it have to do it again for 2GHz?
Intel is upping the voltage of the Pentium 4 in a bid to up the 0.18 micron part's clock speed.
The modified P4s will have a core voltage of 1.75V, an increase of fraction under three per cent from the current voltage of 1.70V. The change, which involves a change from the current B-2 core to a new revision, C-1, will "enable speed improvements", according to Intel's Product Change Notification on the matter, number 1103 (link below). It will also change the CPU's ID code, from 0F07h to 0F0Ah.
The change will affect 1.3, 1.4 and 1.5GHz P4s. Customers will be able to get their hands after 6 April, which is round about the time of the Q2 2001 introduction of the 1.7GHz P4, according to Intel's most recent desktop CPU roadmap.
That suggests that that 200MHz increase from the current peak of 1.5GHz is one of the "speed improvements" the voltage change will enable. Presumably, upping the voltage lets Chipzilla rate more P4's at 1.7GHz, increasing its yield.
JC's News has an interesting take on this. JC points out that upping the core voltage this way has "been long considered... the sign of a 'last ditch effort' to be competitive in chip ramping performance". The site wonders whether Intel has "fatally mispredicted" its yields, and whether that's going to affect the roll-out of 0.18 micron 2GHz P4s, due early Q3.
"Intel had originally predicted that the P4 would reach 2GHz in their current process," says JC. "Doubtless, they were presuming that a voltage hike would be required to get there to ensure arrival at the target speed grade. But the first voltage hike already happened. Did the Intel engineers' projections for 2GHz at 0.18 micron assume clean fabbing for the initial speed grades at the initial voltages?" ®
JC's News' P4 article