question

[Destroyer^]

these have been puzzeling me for a wile and cnt find a good explanation for these anywhere =)

when looking on hdd specs it says like 8mb cache now can any1 tell me wht the cache does? like myne has a 8mb cache, i dont think its the speed as they mostly say 7200 rotations per minute or raptors 10000 rpm

also on the mobos do IDE ports come as standard and only SATA ports u can get? and does SATa ports replace the ide ports or are there both SATa and IDe ports on them?

last question

On proccessors, lets say winchester 64 bit, says it has a 512k l2 cache, i know its double the size of a 32-bit proccessor wht does it do ie to the mobo? is it the quikness of it or memory?

[alexander]

Ok I think on the Cache quesiton it means how far ahead it can plan, I think the most simple idea is on my iPod where you can skip tracks (maybe 4) and then the Hard drive needs to restart and start searching for the tracks ahead. Its kinda like future telling but im not sure....

[Rave]

The idea of processor cache memory is that you can write and read small amounts of data to it much quicker than going out to RAM. 64 bit-ness doesn't really have anything to do with it. In theory more cache helps overall performance but some processors benefit more than others; the Pentium 4 benefits a lot (or more to the point, suffers if it doesn't have enough, like the original P4 Celerons) whereas the Athlon XP and A64 don't really benefit so much from having a lot of cache.

Hard disk cache is the same idea; a small amount of local memory that can be written to much quicker than the hard disk itself. In practice more HD cache memory makes very little difference to the overall performance of the system- but then it doesn't cost much extra either.

Rich :¬)

[Destroyer^]

ty for the help made alot more sense now but wht about the 2nd question

also on the mobos do IDE ports come as standard and only SATA ports u can get? and does SATa ports replace the ide ports or are there both SATa and IDe ports on them?

[Rave]

IDE was the old standard, SATA will eventually replace it. For the time being though boards continue to come with IDE ports because there are still loads of people wanting to use IDE drives. On most (if not all) boards you can use SATA and IDE drives at the same time. Although SATA hard disks are now commonplace, SATA Optical drives are only just starting to show up so IDE ports will continue to be a standard feature for at least the next couple of years. Boards still come with Serial and Parallel ports, and they've been outdated for a very long time.....

Rich :¬)

[GAteKeeper]

More importanty with HDD cache is the fact that most of the time you want a consecutive block off the HDD but not all at once, so you might ask for a file, the HDD will read that file and the rest of the sectors after it (until cache is full) then next time you ask for the next file there is a good chance its in cache and therefore accessing it is really fast.

Memory accesses in computers are slow, the more cache you have the less times you have to go out to main memory, the faster your computer runs. The reason P4s need so much cache is to store enough branch threads so that after a branch in hte code the pipeline (something horendous like 32 instructions) can be re-filled out of cache not memory.

GK

[TiG]

On proccessors, lets say winchester 64 bit, says it has a 512k l2 cache, i know its double the size of a 32-bit proccessor wht does it do ie to the mobo? is it the quikness of it or memory?

the BIT is how large the numbers can be in the system, it refers to the number of binary bits it can deal with. In terms of processing speed it will have very little effect in pure performance compared from going from 16 bit to 32 bit. (many programs reach 2 billion in terms of numbers where not many will reach 2 billion squared)

The other responses have focused on the fact that it is level 2 cache, and ignored the fact that there exists a level 1 cache, which also has a major part to play.

My understanding of this, is that Level 2 cache is much more likely to contain data for the system to work on than the instructions, these are likely to be in the level 1 cache, 32k in AMD's processors or 8k in Intels

The major thing to worry about here is what you will be doing with the computer, normal tasks can be coped with easily with 512k, but if you are doing big complicated tasks like database manipulation etc, it is better to have as much cache as possible.

Thats why some XEON's have 6MB of cache, but games etc just don't need this.

TiG

[Rave]

My understanding of this, is that Level 2 cache is much more likely to contain data for the system to work on than the instructions, these are likely to be in the level 1 cache, 32k in AMD's processors or 8k in Intels

Actually all AMD processors (since the K7 at least) have 64K of L1 Instruction cache and 64K of L1 Data cache. Most Intels have 8K of each although the Prescott core upped one of them to 16K (I forget which off the top of my head).