Intel Pentium M 780 socket: Socket 479

What the Pentium M 780 is

The Pentium M 780 closed the Dothan 533 MT/s series in July 2005 with a 2.26 GHz rating. Its single Dothan core maintains that frequency under sustained load, as the architecture provides no turbo range above base. The attached 2 MB L2 cache gave demanding notebook tasks of the period, from large spreadsheets to photo catalogs, more on chip headroom than Banias predecessors. Production used the 90 nm process with 144 million transistors on an 87 mm2 die, values TechPowerUp documents for the entire 730 to 780 set.

The top clock derives from a locked 17x multiplier applied to a 133 MHz base clock and delivered over a 533 MT/s front side bus. System firmware governs bus timing and SpeedStep transitions, dropping voltage and frequency at rest and reapplying full speed on demand. The core executes MMX, SSE and SSE2 with the NX bit and stays in 32 bit mode, matching the driver base that Sonoma notebooks carried through their service life.

As the last and fastest 533 MT/s Pentium M, the 780 sits above the 730 at 1.6 GHz, the 740 at 1.73 GHz, the 750 at 1.86 GHz, the 760 at 2.0 GHz and the 770 at 2.13 GHz. Cache size, bus rate and the 27 W limit do not shift across that ladder, leaving frequency as the single separator. Intel sold the 780 in socketed Micro-FCPGA form covered here plus a soldered Micro-FCBGA twin for socketless boards. Used examples therefore mark the ceiling of the Sonoma Pentium M line before Core era platforms replaced it.

Socket and motherboard compatibility

Board fitting relies on a lever ZIF socket with 479 holes in mPGA479M order. Pins slide in freely, then lever travel draws them into wiped contact that survives notebook heat cycles. One hole stays reserved, so 478 lines carry signals, a physical reason Socket 478 desktop boards cannot host the part. The Socket 479 page records the hole total and the mPGA478C name variant.

Sonoma boards on 915 series mobile chipsets remain the intended host for the 780. Their logic runs the required 533 MT/s link and couples it to DDR2 memory. The earlier 855 series, aimed at 400 MT/s Banias links, cannot support a 533 MT/s Dothan flagship even when insertion looks correct. How socket, chipset family and BIOS revision interact is laid out in the Socket vs chipset: what decides whether a CPU works guide.

BIOS tables must list the exact sSpec of the fitted sample. The 780 shipped as sSpec SL7VB, a string notebook makers added to support lists for qualifying boards. Without that entry the system can fail POST or misclock the chip. Its Micro-FCBGA counterpart solders through balls straight to the board and never touches a socket, keeping the used socketed pool separate. The 2006 Socket M follow on altered one pin site for Core processors, so its chips are incompatible here.

Memory, PCIe and cooling

Memory access for the 780 runs as DDR2 through the board chipset. The CPU die integrates no controller, so slot counts, density ceilings and validated DDR2 400 or DDR2 533 modes belong to each notebook design. Populating the documented configuration with approved modules sustains the 533 MT/s front side bus when code spills from the 2 MB L2. Manual limits for the precise model govern any upgrade attempt.

Off chip I/O follows the chipset as well. The processor provides no PCI Express lanes, so its 533 MT/s front side bus hands transactions to the chipset for graphics and slots. Sonoma systems paired this CPU either with chipset graphics or with a board mounted discrete mobile GPU, and driver packages for both came from system or chipset channels. Expansion behavior is therefore a board attribute rather than a CPU attribute.

Heat removal uses vendor heat pipe assemblies rated at 27 W. A plate contacts the exposed die, pipes carry load to exhaust fins, and fan firmware tracks curves calibrated for that band. Maintenance needs gentle handling of the bare silicon, complete removal of aged paste and a thin replacement layer under even plate pressure. Clearing lint from intakes and fins usually brings boost behavior and acoustics back near stock on older units.

Upgrade paths

Inside Socket 479 the 780 is the highest locked step, so movement runs downward where firmware allows. The 730 at 1.6 GHz, the 740 at 1.73 GHz, the 750 at 1.86 GHz, the 760 at 2.0 GHz and the 770 at 2.13 GHz all share its 2 MB cache, 533 MT/s bus and 27 W envelope and fit the same heat pipe. Such swaps help only for spare sourcing or clock matching to a board limit, and each sSpec still needs board table support. No higher Pentium M exists on this bus.

Any step past Pentium M demands Socket M. Core Duo and Core Solo processors need the revised pinout plus 945 series mobile chipsets in a newer notebook or board. The Socket vs chipset: what decides whether a CPU works guide outlines the chipset and firmware proof needed before either staying or switching. Where daily responsiveness lags, memory growth and a solid state drive on the current board often return more than exchanging one Dothan multiplier for another.