Opteron has also undergone some exterior changes, which made it even more attractive for high-performance workstations. First of all, I have to draw your attention to the package cover, which protects the fragile die against damaging when the coolers are installed on top of it. This time, AMD couldn’t do without this cover, because the Opteron dies are made with SOI technology and are extremely fragile. Moreover, besides the built-in thermal diode, Opteron has also acquired a special anti-burn protection circuit called Thermtrip. Although there is nothing really exclusive behind this name: when the CPU reaches some critical temperature, it simply shuts down.

I also have to stress that in its Opteron processor AMD paid special attention to memory error code correct, which is very important for server use in the first place. The memory controller integrated into the CPU supports parity control and ECC, also ECC is implemented in the L1 and L2 caches. By the way, the ECC algorithm in Athlon XP processors was implemented only for L2 cache, while L1 cache supported only parity control scheme.

According to the marking nomenclature used by AMD for Opteron processor family, there are a few product lines within this family now: Opteron 14x, 24x, 8xx. Note that Opteron 14x doesn’t work in two-way systems, Opteron 24x can be used in max. 2-way systems, and Opteron 8xx is intended for 4- and 8-way configurations. These differences between three Opteron lines are very illustratively marked by their pricing. For instance, a uniprocessor Opteron modification costs about the same as the top Pentium 4 CPU, which once again indicates that uniprocessor Opterons are intended to compete with the top Pentium 4 models in the workstation market.

The architecture of Opteron processors implies the HyperTransport controller supporting three corresponding buses with up to 6.4GB/sec bandwidth each. These buses serve as a system bus and inter-processor bus. However, you should understand that you do not need three HyperTransport buses if there is a uniprocessor Opteron system. Since the configurations with only one Opteron processor do not need any inter-processor connection, only one HyperTransport is involved. This bus connects the CPU and the chipset. Here we should certainly say that Opteron 1XX processors are shipped with only one fully-functional HyperTransport bus, which explains their considerably lower price compared with Opteron 2XX and especially with Opteron 8XX. This is exactly why you will never be able to use low-cost Opteron CPUs in multi-processor systems.

In conclusion to my story about uniprocessor Opteron CPUs, I would like to dwell on the differences between this processor and the upcoming Athlon 64 also based on the 8th generation architecture, which is due in September 2003. In fact, the differences are not so numerous. There will be no architectural differences. In particular, you will not be able to use Athlon 64 in multi-processor configurations, because this processor, like Opteron 1XX, will have only one fully-functional HyperTransport bus. This way, the only distinguishing feature between these two processors will hide in the memory controller. While Opteron 1XX supports dual-channel DDR333 SDRAM with ECC, Athlon 64 will feature simpler memory subsystem. The memory controller of the future desktop processor from AMD will be able to work with only one memory channel and will not support ECC, however, it is very likely to acquire DDR400 SDRAM support.