Intel Pentium M 740 socket: Socket 479

What the Pentium M 740 is

The Pentium M 740 arrived in January 2005 as the second step in the Sonoma wave of Pentium M processors. It runs a single Dothan core at 1.73 GHz with no turbo mode, so the rated clock is the sustained clock under load. The core integrates 2 MB of L2 cache, which gave notebooks of that period more on chip storage for office suites and browser tabs than the earlier 1 MB Banias design allowed. Intel fabricated the die on the 90 nm process with 144 million transistors on an 87 mm2 die, figures TechPowerUp records for each SKU in the 730 to 780 range.

A 13x multiplier combined with a 133 MHz base clock produces the 1.73 GHz rating on a 533 MT/s front side bus. The multiplier stays locked, so the mainboard sets the bus and the processor follows. SpeedStep lowers the clock and voltage at idle to extend battery time, then returns to the full rate when work resumes. The design supports MMX, SSE and SSE2 with the NX bit, and it has no 64 bit mode, which matches the 32 bit software stack that Sonoma notebooks shipped with.

Intel placed the 740 just above the 1.6 GHz 730 in the 533 MT/s stack. Both share the same 27 W thermal rating, the same 2 MB cache and the same bus, so the difference is clock alone. The SKU was sold in a socketed Micro-FCPGA package covered here and in a soldered Micro-FCBGA twin for boards built without a socket. A used notebook with a 740 therefore carries a modest clock gain over the entry 730 while keeping heat and battery behavior in the same class.

Socket and motherboard compatibility

The 740 seats in a lever operated ZIF socket with 479 holes in the mPGA479M arrangement. Pins enter with zero force and the lever cam then grips them, which lets a socketed mobile processor move between boards without solder work. One hole position remains reserved, so 478 contacts carry signals, and that layout detail keeps Socket 478 desktop boards from accepting this chip. The Socket 479 page documents the hole count and the mPGA478C alternate name.

Sonoma notebooks built on 915 series mobile chipsets form the correct home for this model. Those mainboards run the 533 MT/s bus the 740 expects and provide DDR2 slots alongside it. Boards built on the older 855 series for 400 MT/s Banias traffic do not suit a 533 MT/s Dothan chip, even when the package seats cleanly. The Socket vs chipset: what decides whether a CPU works guide describes why a matching socket opening never guarantees a working combination.

Firmware must name the exact sSpec stepping before a board counts as compatible. Intel shipped the 740 as sSpec SL7SA, and notebook vendors copied that code into BIOS CPU tables. A board without the entry can refuse to boot or report the wrong clock. The soldered Micro-FCBGA twin of the 740 mounts directly to the board with balls instead of pins, so it never appears in the socketed used market. Socket M followed in 2006 with a moved pin for Core processors, and Socket M boards do not accept Pentium M parts.

Memory, PCIe and cooling

Memory on a 740 system is DDR2 installed through the board chipset. The processor contains no memory controller, so the notebook maker fixes the slot count, the per slot ceiling and the approved DDR2 speeds. A pair of maker approved modules in matching slots keeps the 533 MT/s front side bus supplied during L2 misses. Many Sonoma boards accept DDR2 400 or DDR2 533 under different chipset straps, and the service manual for the exact notebook states the limit.

PCI Express lanes do not originate in this processor. A 533 MT/s front side bus carries processor traffic to the chipset, while graphics and add in cards attach on the chipset side of the board. Some Sonoma designs use chipset graphics and some add a separate mobile graphics chip on the board, but in both cases the graphics driver comes from the board or chipset vendor rather than from the CPU.

Heat stays within a vendor heat pipe assembly rated for 27 W. A copper plate sits over the bare die and feeds pipes that run to a blower outlet at the notebook edge, with fan tables tuned for that thermal class. The die has no heat spreader, so paste replacement calls for a thin coat and light even pressure on the plate screws. Clearing dust from the fan and fins restores the stock temperature curve on machines that have grown loud after years of use.

Upgrade paths

A board that already runs a 740 can shift within the same socket where firmware allows. The 730 at 1.6 GHz sits below it, while the 750 at 1.86 GHz, the 760 at 2.0 GHz, the 770 at 2.13 GHz and the 780 at 2.26 GHz sit above it with the same 2 MB cache, the same 533 MT/s bus and the same 27 W envelope. Cooler hardware therefore stays valid across the swap, and the change is a locked multiplier step rather than a platform change. Buyers still need to match the donor sSpec against the maker support list before ordering.

Movement beyond the 780 leaves Socket 479 entirely. Core Duo and later mobile families call for the Socket M successor with its altered pin and newer chipset, which means a different notebook or a different mainboard. The Socket vs chipset: what decides whether a CPU works guide lays out how to confirm chipset and BIOS coverage before paying for parts. On machines that feel slow in general tasks, added memory and a solid state drive often deliver more than a small clock rise inside the same socket.