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Review: AMD Athlon XP 1800

by David Ross on 10 July 2003, 00:00


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AMD Athlon 1800XP+ Processor

The Athlon 1800XP CPU is a 1.53GHz clocked CPU but it has a new name, a PR name, this is basically the performance rating of the CPU, this processor is equivalent to an 1800 MHz Thunderbird based core. This if you ask me is pretty damn quick! There are a lot of enhancements which AMD have made to this new core. The first thing which you will notice with this CPU is that the "holder" for the core - the part which used to be a purple ceramic colour is now a brownish colour the reason for this is that AMD have now made this out of an organic matter, this is a lighter and also seems a lot thinner. Will we see an organic matter based Duron soon? We can only wait and see.

The key new factors with this new core are what AMD calls Quantispeed. Some people think that Quantispeed is just the name for the new processor rating system, however it covers a whole list of new features on this Thunderbird/Duron evolution of their 7th generation x86 core.

First up we have enhancements to the processor pipeline giving the new core a slightly higher IPC than TBird/Duron and allowing it to do more work for a given clock speed.

Next up we see AMD touting the floating point unit of their core and with good reason. AMD deserve much praise for the FPU unit in this processor family and it's the quickest ever x86 FPU unit in any processor.

The 3rd part of Quantispeed is the data prefetch unit in the new core. The CPU is intelligent enough to make a very educated guess at the next block of data that the CPU will be working on. It prefetches it into L1 before the instruction operates on it meaning that the data is there automatically and it doesn't have to waste cycles getting the memory after the instruction is already in the pipeline. Sometimes it'll guess wrongly and the data wont be in L1 meaning a possible trip out to system memory or even disk, but the CPU has a low miss rate and overall performance increases.

The fourth and final part of Quantispeed is modifications to the Transition Lookaside Buffers, part of the L1 and L2 cache arrangement. The buffers hold information about the data held in memory. In CPU's that implement Quantispeed, the buffers are larger and exclusive between L1 and L2 caches, meaning that the TLB buffer in L2 doesn't mirror the L1 TLB. This helps reduce cache misses and means the CPU has access to the correct data quicker and for more of the time, improving performance.

All in all the Quantispeed enhancements to the core add up to a healthy performance increase and allow AMD to legitimately use their new performance rating and rate a 1533MHz CPU that uses Quantispeed as fast as a 1800MHz Thunderbird CPU. While this may or may not be entirely accurate since an 1800MHz Thunderbird running at 10 x 180 should give superior performance to a stock clocked 1800XP, the rule holds quite well.

When I first got the unit I decided to do some serious testing, I had been playing with the 2 GHz P4 which we had in the test lab, and we were impressed with the new format and speed (Ed. the review should be up soon!). As this is "only" a 1.53 in essence we wondered how it would perform against other platforms, what I can say, so far we are very impressed. The CPU itself is the same as any other Socket A CPU. You plug it in, you put your heatsink on and run it. Simple really. ;)