Why does AMD have so much L1 Cache?

[Spikesoldier]

How can AMD have 128KB of L1 cache and Intel have anywhere from 32KB to 24KB of L1, and not have a performance increase over intel?

And doesn't this add to the cost of making the chip?

 

[Wetling23]

<< ...and not have a performance increase over intel? >>



What benchmarks have you been reading?

 

[MoFunk]

No performance increase over Intel? Hmmm Interesting.

 

[mrman3k]

Keep in mind that L1 cache is the first RAM the processor uses when it is doing its calculations, more is usually better however the processor has to take full use of the cache in order to see any improvement.

 

[LiLRiceBoi]

umm...amd can outperform an intel at the same clock speed in almost every area...

 

[CTho9305]

<< How can AMD have 128KB of L1 cache and Intel have anywhere from 32KB to 24KB of L1, and not have a performance increase over intel?

And doesn't this add to the cost of making the chip? >>


amds are faster. yes, it adds to the cost.
the p4 has 8kb L1, but also a specialized cache that intel doesn't release the true size of.

anyway, almost always, athlons beat similarly-clocked intel chips.

 

[AndyHui]

Latency.

The larger then L1 and L2 caches, the longer it takes for the processor core to decode addresses and access the data located within the cache. Sure, you have a larger cache with more stuff in it, but it takes a correspondingly longer time for you to look through it.

One of the reasons the Intel Pentium 4 has such as small L1 cache is that it is designed for sheer speed. To access it takes several clocks less than the access on an Athlon processor. You also need to take into account that Intel decided to make a design change with the execution trace cache. The ETC is really an L1 instruction cache. Although Intel won't say how large it is, we suspect that it is somewhere in the order of 96KB or so.

 

[Spikesoldier]

I didn't say that AMD needs the extra cache just to match intel as you may be thinking but given two equal chips probably a P4 1500 and XP 1500+, I dont see why AMD doesnt pull far away since it has more cache total.

 

[AndyHui]

But the two processors are FAR from equal.

Let's just consider the cache for a moment. The Pentium 4 features a 256-bit wide bus to the L1 and L2 cache. The AthlonXP features only a 64-bit wide bus. The Pentium 4 requires several LESS clock cycles needed to access the cache as opposed to the Athlon.

A 400MHz system bus for the Pentium 4, and a 20 stage pipeline. A 266MHz system bus for the AthlonXP and a 12 stage pipeline. All these combine to make BIG differences.

Since cache is silicon real estate, then yes, it would add to the cost of production. However, AMD probably calculated the trade-off and thought it would be better with that much cache. With AMD's exclusive cache scheme, the use of the L1 and L2 caches is quite efficient as you can store the maximum amount to keep the processor fed.

Look at things in a balanced way, and look at the entire package.

 

[EXman]

<< A 400MHz system bus for the Pentium 4, and a 20 stage pipeline. A 266MHz system bus for the AthlonXP and a 12 stage pipeline. All these combine to make BIG differences. >>

These are minomers as the latency issue andalso the 20 stage pipeline has to scram as piplines do well you get the picture. Why Did I hear nothing about the P4 very low IPC compared to the T-bird? Reason their chips are so fast is cause they do not do as much work clock for clock Best thing going for it is a lack of widespread use of Via chipsets!

 

[ForsakenGemini]

clock cycles, clock cycles, blah blah blah...Mhz ­ power...

-Forsaken