Intel E7525 Xeon Core Logic
Tumwater is a chipset we've seen before. It includes E7525 principle ASIC (which supports SLI, or used to), Intel 6700PXH PCI-X segment bridge and either Intel ICH5R I/O controller or Intel 6300ESB I/O hub. We'll go through each in turn, before summing the lot up.Intel E7525 Memory Controller Hub
E7525 is a workstation-class memory controller that houses the CPU bus interface that the Xeons ride. It supports Paxville DP, but also Nocona, Irwindale and LV Xeons, too. Indeed, we reviewed it with Nocona back when that CPU was released. The shared CPU bus connects to the single dual-channel DDR2-400 memory controller. That controller makes registered and ECC memory mandatory, at up to 400MHz effective speed and 16GiB max capacity. Interestingly, you'll see most vendors of E7525 boards require memory with gold-plated contacts, presumably for signalling reasons (especially crucial for workstation and server hardware stuffed full of DIMMs, we imagine).The 1077-ball chip package also houses a 24-lane PCI Express host, which splits them up 16+4+4. The first 16 lanes are all routed to a 16X electrical slot on the mainboard, the second four are for any PCI Express I/O bridges, with the last 4 to be split as the mainboard vendor requires. Most plumb the last four lanes up to another 16X slot and leave it at that.
Downstream from the CPU interface, PCI Express controller and memory controller, the MCH has an 'Intel Hub Interface 1.5' (266MiB/sec max) connection to the I/O bridge on the far side, be that ICH5R (a bit old for a modern chipset, we think) or 6300ESB (ICH5-esque, too). Because of PCI Express, there's also capacity for the chip to talk to an Intel 6700PXH, too, which we'll talk about shortly.
In short, the I/O connection ability the E7525 has is pretty good, but then the I/O controllers you can pair it with are old and a bit creaky as far as things like SATA support go, but at least its backed up with decent PCIe and server-friendly PCI-X connectivity. What worries us most is the shared CPU bus and tardy memory controller. More on those later, as we analyse platform performance.
Intel 6700PXH PCI-X segment bridge
The 6700PXH bridges PCI Express on the host side to a pair of PCI-X segments on the I/O side. The two segments are PCI-X Mode 1 (up to 133MHz) compatible and they'll communicate with 32-bit and 64-bit devices, although not at the same time. Most board vendors will set the chip up with two 64-bit segments and the corresponding slots, each at different speeds. It seems like the 6700PXH will consume all four lanes the E7525 can give it, for the PCI-X bridging.Intel ICH5R
The Intel ICH5 and ICH5R were introduced along with the desktop-focused i875 'Canterwood' chipset for Socket 478 Pentium 4s, back in April 2003, over two and a half years ago. Not quite the I/O processor you'd expect to see on a modern workstation chipset then, really. ICH5 was the first I/O chip from a major chipset vendor to integrate a SATA controller for disk drives, though, and its age means that its long been qualified and favoured in situations where reliability of operation is key. However that really doesn't excuse not using something newer, with more relevant features (like NCQ and SATA2, which more and more enterprise-class disks are sporting) and more wide-reaching I/O ability.Further, ICH5R only has two native SATA links, so only two disks can attach to the chip. On a modern E7525 mainboard, therefore, you'll see the vendor add extra I/O ability and features via extra ASICs. We mentioned the 6300ESB earlier as being ICH5-esque, and that's completely true. The other I/O processor that E7525 can connect to is basically just the ICH5 plus a PCI-X segment bridge. But with vendors likely always using the PXH on Paxville-supporting mainboards, you'll likely never see them spec the 6300ESB, really. It was first qualified for use with i875P, too, in workstation applications, so its age is just as apparent.
Summary
When you consider the chipset as a whole, you can't help but think the PCI Express ability is the only shining light. Everything else just doesn't have the ability or speed that you'd really want to pair with CPUs that sport two cores and HyperThreading to boot. Lots of potential processing power at the top end, with plenty of PCI Express for expansion and support for the latest graphics hardware, but with everything else decidedly two or more generations old and showing their age. Intel's reliance on an off-CPU memory controller rarely does the company favours these days, so additionally seeing E7525 limited to DDR2-400, when registered-with-ECC, 2GiB, DDR2-533 sticks are easily found and readily available, is a bit depressing. Even registered, ECC-supporting DDR2-667 sticks are available from big-name memory vendors, although only up to 1GiB per stick it seems.While enterprise class hardware doesn't need to evolve at the same pace as its desktop counterpart, forcing the vendor to spend more on peripheral ASICs to get a mainboard up to modern standards, both in financial terms and in the area of board design and PCB complexity, is never the greatest thing. Workstation boards like the one in the Armari system used to evaluate Paxville have to resort to piling on the extras to make themselves attractive. And that's in spite of the limitations seen with the CPU and memory bus.
Let's take a look at the E7525-based system that we used to evaluate Paxville in more detail.
