Worldwide server shipments showed "modest growth" during the last quarter of 2007, according to the latest numbers from analyst group IDC. Yet clearly, much of the growth happened at the lower end of the market, in x86-based Windows and Linux PC servers.

All told, server revenues picked up 2.4 percentage points from the final quarter of 2006 to reach $15.7 billion during the last three months of 2007. But Microsoft Windows-based servers shot up 6.9% in revenues and 9.8% in shipments during that same time.

Meanwhile, revenues from the sale of Linux servers rose even higher, to the tune of 11.6%. On the other end of the scale, though, revenues from Unix servers showed growth of only 1.5%.

In its written statement summing up the results from the final quarter of 2007, IDC did not release the unit shipment numbers for either Linux or Unix servers. Yet the x86 market overall increased 7.6% in revenues over the quarter and 10.3% in unit shipments, according to IDC statistics.

Since unit shipment growth was somewhat higher at 10.3% for x86 servers than the 9.8% growth figure for Windows servers only, it would appear that shipment growth must have been faster on the Linux side.

Microsoft Windows servers accounted for 36.6% of all revenues, in comparison to only 12.7% for Linux servers.

Also during the quarter, the server blade market leaped an astounding 54.2% in revenues and 35.6% in shipments. The blade market consists of x86 as well as RISC and EPIC systems.

Although IDC's summary did not break out the numbers for IBM mainframes, either, sales of mainframe servers were reputedly slow during the prior quarter, as customers awaited the System z10 models announced by IBM last week.

"The next generation of IBM mainframes, the System z10 Enterprise Class, will extend the platform's inherent strengths while improving the positioning of the platform for new workloads," wrote John R. Phelps and Mike Chuba, in a new report by Gartner.

The Gartner analysts cited five new features on the hardware size aimed at reducing overhead and raising performance: support for the 1 MB page frame size to reduct member management overhead; at least 50 new instructions to improve compiled-code efficiency; InfiniBand coupling links to speed parallel sysplex intersystem communication at greater distance; a HiperDispatch feature to reduce task switching overhead; and implementation of hardware decimal floating point implementation, for up to a tenfold performance improvement in instruction execution.

Meanwhile, by IDC's numbers, IBM -- a vendor with entries across the high, midrange, and low ends of the market -- remained the top seller in the server market overall during the final quarter of 2007, with a market share of 36.7%.

IBM was followed by Hewlett-Packard at 27.7%, Dell at 10.1%, Sun Microsystems at 9.3%, and Fujitsu/Siemens at 4.3%. "Other" vendors accounted for the remaining 11.9% of the worldwide server market.