CPU lacks pins, uses PCIe plugin. Consider alternatives.
CPU lacks pins, uses PCIe plugin. Consider alternatives.
I understand I didn’t do a great job with the photo, but just be honest. The only reason I mentioned this was because I accidentally bent a pin, which really bothers me. Luckily, I managed to fix it.
This trend had been present with older Pentium II and early Pentium iii models. The shift was mainly due to poor pin density and the ability to relocate the cache inside the CPU die.
At elevated frequencies, the connections between the CPU silicon die and other components need minimal length. For parts such as RAM, the links between CPU and RAM use numerous wire pairs (for instance 64 pairs). It isn't just the individual wires in each pair that must match, but also that all pairs maintain uniform dimensions. With your slot layout, wire lengths become inconsistent from the CPU die to the connector pins on the edge. This complicates efforts for manufacturers to standardize wire lengths across boards, making it difficult to balance the total length of each pair. It also hinders routing strategies where wires are directed differently—some to PCIe slots, others to RAM slots. On contemporary CPUs, the RAM area sits on one side while PCIe paths run beneath; thus wires must travel straight down to their designated slots. Intel adopted this design to accommodate cache chips close to the CPU, as earlier manufacturing lacked the precision to fit large cache units without defects. Producing smaller processors allowed higher yields and improved performance, with cache chips handled separately. These cache chips, though large, contain repetitive patterns; defects could isolate problematic sections, enabling chip producers to market smaller quantities with fewer faulty units. At the time, frequencies were much lower—133-200 MHz for SD-RAM and DDRAM—compared to today’s 1800 MHz and above. Precision and quality now surpass those standards.
Some Dell Precision workstations incorporated processor cards for the second CPU, yet they remain socketed. It’s hard to grasp the reasoning behind this design choice. While it does conserve space—which is evident in these large machines—it introduces numerous complications. Personally, I find the sockets and pins for microprocessors surprisingly robust. Inserting processor cards significantly complicates an already complex board layout. We’re working with multi-layer boards (or possibly even more advanced) and densely packed BGA packages. The frequencies involved are typically in the microwave range, making layout precision essential to prevent timing errors and interference. Worse still, CPUs draw substantial current—generally around 100 A. This adds another layer of concern. Although I don’t typically handle high-speed digital projects, I’ve built several high-speed amplifiers where even a millimeter of trace spacing can determine success or failure. A few picofarads of stray capacitance can tip the balance between compliance and instability. If you still believe processor cards are worth considering, refer to Linear Technology Application Note #47. Keep in mind that the rise and fall times here are far quicker than anything discussed in that note. Adding processor cards makes many challenges more severe. Moreover, the sheer number of pins—often exceeding 1000 per CPU—is daunting. You might try reducing pins on the connector, but you’ll still face a large number of connections. No thanks!