P4 extreme why add L3 cache?

[nimo]

P4 went from 256k L2 to 512K L2 and the performance increase for drastic

Why not bump L2 cache again?

I donno much about CPU design so if this question really stupid don?t rain on me too hard

 

[DivideBYZero]

Cause then you only have to repackage a Xeon, rather than fab a new CPU.

P4EE is a 800Mhz Xeon with HT.

 

[sao123]

increasing the L2 to 1MB is what defines prescott along with other features such as 90nm, 13new instructions, HypThrd 1.1, etc. Since that cpu may not be compatible with older Mobo's. Repackaging the Xeon with the 2MB L3, as a 478 pin P4 is the most effective solution. the key here is that the current Xeon is based on Northewood, which guarantees compatability with current Mobo's.

 

[bunnyfubbles]

cache comes in different levels, L1 cache on P4's is actually very small (only a few KB) but on the flip side it is very fast. L2 is still fast but adding more doesn't always help because with more caches the further data has to go (larger latency). The P4 did increase from 256KB of L2 cache to 512KB, but at the same time it also shrunk in size from 180nm to 130... L3 cache is just another level, allowing for a large amount (2MB) but it isn't as fast as L2 cache would be but it should certainly help reduce latency from the system RAM to the CPU.

 

[DeeTees]

If memory serves me AMD did the same thing when the K6-2 could not compete with the PII. They came out with the K6-3 (with L3 cache) and i'll be durned, it out performed the PII on many tasks at the same clock speed.

Who said imitation is the highest form of flattery?

 

[Jeff7]

Originally posted by: DeeTees
If memory serves me AMD did the same thing when the K6-2 could not compete with the PII. They came out with the K6-3 (with L3 cache) and i'll be durned, it out performed the PII on many tasks at the same clock speed.

Who said imitation is the highest form of flattery?

If I recall, it was the K6-3 that introduced the L3 cache; the K6-2 only had L1. The K6-3 had the added advantage of the L2 cache on the chip, running at CPU speed. The cache on the motherboard became Level 3, but it only ran at the frontside bus speed, and it had higher latency. If my experiences with those CPUs was any indication, they were often hampered by rather inferior chipsets.

 

[JWade]

I had a k6-2 and a k6-3 at one time, then a slot-a and then socket-a, and inbetween all those was the pentium, pentium2, pentium3 and xeon and xeon2. The k6-3 had the L2 and the cache on the board became the L3. Looking at some of my old benchmark scores the k6-3 450 performed on par with a P3 500, in the benchmark scores before anyone flames me on it. It defiantely outperformed a K6-2 500 chip. Only difference being the processor.