IBM drops Istanbuls into big Opteron box
Three or four sockets, 18 or 24 cores
Big Blue has begun certifying Advanced Micro Devices' six-core Istanbul Opteron processors for its System x product line, and on Tuesday announced support for the processor in its fattest Opteron box, the System x3755.
The x3755 is a four-socket, rack-mounted server that comes in a 4U chassis, and was just updated in March with quad-core Shanghai Opteron 8384 processors. The BladeCenter LS22 and LS42 blade servers were announced as supporting some Shanghai chips in February and then others in June.
Thus far, IBM has been a little slow on the uptake for the Shanghai and Istanbul generations, at least when compared to its enthusiastic support for Intel's quad-core Nehalem EP Xeon 5500 chips.
The x3755 is the first IBM box to get official Istanbul support, which requires BIOS tweaking as well as certification by Big Blue. IBM has not yet put the Istanbuls into the 1U, two-socket x3455 rack server or its brother, the 2U, two-socket x3655. The LS22 and LS42 blades also have yet to get the Istanbuls.
IBM does not sell Opteron-based tower servers, and neither has it made Opteron variants of its iDataPlex hybrid rack-blade designs.
IBM today announced that it will support the 2.4GHz Opteron 8431 and 2.6GHz Opteron 8435 in the x3755 box. Both of these chips are standard 75 watt parts, not the new Special Edition (SE) and Highly Efficient (HE) variants of the Opterons that are rated at 105 watts and 55 watts, respectively. AMD announced SE and HE versions of the Istanbul Opterons on Monday, and is expected to debut 40 watt Extremely Efficient (EE) parts before the end of the third quarter.
The x3755 server sports up to 128GB of main memory (32 DDR2 slots) and has an integrated SAS disk controller, dual-port Gigabit Ethernet NIC, and seven I/O slots - four PCI-Express (one x16, two x8, and one x4), two PCI-X, and one HyperTransport Extender (HTx).
The x3755 also has something IBM cooked up called Xcelerated Memory Technology, which lets memory in all eight DIMMs linked to each processor socket run at full 667MHz speeds instead of having to cut back to 533MHz. The net effect of XMT, says IBM, is that a machine with less memory capacity can do more work than another Opteron server design where more memory capacity requires the speed to be dropped.
In addition, the x3755 has a feature called the CPU Pass Thru Card, which is a HyperTransport accelerator co-processor that IBM added to the System x3755 a few years back. This accelerator speeds up the HyperTransport Links between the three processor sockets that have the Opteron 8000 series chips plugged into them such that, for some workloads, three 8000 series chips actually do more work than customers would be able to get out of four 8000s.
Yeah, that sounds counterintuitive, but there's a lot of overhead in SMP systems and sometimes the extra overhead of a socket is not worth the trouble.
There's a certain amount of skepticism about the CPU Pass Thru Card, but for what it is worth, here's one benchmark from 2007 and a more recent one from this year that show it doing what Big Blue says it does.
AMD has added a new feature with the Istanbul Opterons called HT Assist, which reserves 1MB of the L3 on-chip cache to act as a directory for all of the cache lines in the processor complex on the four-socket machine. Instead of broadcasting to the other three chips in the complex for cache information, each chip can look it up in its local cache-line directory. HT Assist is implemented at the BIOS level, and on memory-intensive workloads, AMD says it can increase throughput substantially - as much as 60 per cent on the Stream HPC benchmark, probably less on database workloads.
It would be interesting to know if IBM's CPU Pass Thru Card is really a cache directory of some sort. Whatever it is, the CPU Pass Thru Card only costs about $100, and it can mean not paying a several grand for that fourth Opteron 8000 to get similar performance.
The base System x3755 with two 2.4GHz Istanbul Opterons, 4GB of memory, no disk drives, and no operating system costs $9,011. Adding an additional Istanbul, the CPU Pass Thru Card, and boosting the memory to 48GB drives the price up to $13,842.
Taking out the CPU Pass Thru Card and putting in the fourth Istanbul chip puts the price of the x3755 at $16,961. Add another $530 per processor socket if you want the faster 2.6GHz Istanbul Opterons in the x3755.
IBM will begin shipping the Istanbul variants of the System x3755 server on August 26. Red Hat Enterprise Linux, Novell SUSE Linux Enterprise Server, Microsoft Windows Server, and Sun Microsystems Solaris 10 are all supported on this box. ®