Cacheable area: ALI-V, K6-3(+)

Discussion relating to Socket 7 hardware.
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DonPedro
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Cacheable area: ALI-V, K6-3(+)

Post by DonPedro »

.
hello folks,

a lot of "urban legends" seem to prevail in a lot of posts here about the cacheable area given an ali-5 board housing a K6-3(+) or K6-2+ cpu.

on the german asus-website, there is a great faq-section.

faq #045 http://www.asuscom.de/support/FAQ/faq04 ... e_area.htm makes an end to all the rumors:

it states:
- a K6-3 cpu has a cacheable area of 4 GB.
- the cacheable area of the onboard cache of an ali-5 board (P5a, P5a-b) is defined by

a) chipset revision
b) cache size

ALI V - Revision...............Cache - size.........Cacheable Area
M1541/42 A1 / Rev. D.....512kB or 1MB.......128MB
M1541/42 A1 / Rev. E.....512kB or 1MB.......128MB
M1541/42 A1 / Rev. G.....512kb.....................512MB
M1541/42 A1 / Rev. G.....1MB........................4GB

so even if one disables the onboard-cache but uses a K6-3(+)/2+ type cpu, caching will be fully functional for all installed RAM.

again, the K6-2+ (128kb on-die cache) has the same cacheable area of 4 GB as the K6-3(+) cpu (256kb on-die cache).

so disabling the "3rd-level" onboard cache when using a K6-3(+) or -2+ cpu is a question of how you use your computer: I heard rumors :wink: that gamers don't benefit of an active 3rd-level cache, they eventually will have higher frame rates with the 3rd-level cache disabled. those who use their computer for word-processing, image-processing, etc might improve performance by enabling the 3rd level cache.

quod erat demonstrandum.
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KachiWachi
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Post by KachiWachi »

Even though they may have the same cacheable area, you still have to consider -

- number of cache lines available
- speed of the cache (on-chip, full speed vs. Motherboard cache, FSB speed)

My machine actually slows down a bit with the Motherboard cache enabled...see my post on that here.
DonPedro
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cache lines

Post by DonPedro »

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KachiWachi, well, of course you are right, but what you are pointing at does not have an impact on the size of the cacheable area.

what you are referring to belongs more to answer questions whether, in the end, it is "better" to raise the fsb to 105mhz with a multipier set to 5.5x or go along with a multiplier of 6x at an fsb of 100mhz (577.5 vs 600). but that is a completely different question ..... and of course will be answered again by what applications you are using.

I have absolutely no idea about the "cache-lines" issue. could you shed some light on it regarding the comparison of a k6-3(+) vs k6-2+ cpu (256kb cache vs 128kb cache)? also do you have some bench results showing the difference?


OFF topic:

in the past weeks I have done very heavy benching regarding the impact (cross-impact) of using combinations of

- memory settings (222x vs 333x)
- enabling/disabling of "3rd level" onboard cache

I am using about 10 different benchmark-programs to find out

- how much of a difference can be experienced
- and what applications are influenced by what degree in what direction by what combination of settings.

I selected the bench-programs that way that by cross-contrasting the results (degree, direction) with each other I will hopefully also reveal the validity of the so called "synthetic" bench programs which are so much referred to and relied upon by almost everybody. sometimes even me.

maybe we are right ......

once I am through with it (THAT is work, men, really!!) I will start a new post and let everybody know.

humbliest
peter
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KachiWachi
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Post by KachiWachi »

Explanation of the system cache at "The PCGuide" -> http://www.pcguide.com/ref/mbsys/cache/func.htm
DonPedro
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cache as cache can

Post by DonPedro »

.
a very interesting and enlightening read indeed (to be honest, I overflew some parts).

but I could not find any information that disputes my remarks on cacheable area or cache performance differences between k6-3(+) and k6-2+ cpus.

maybe I missed it.
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KachiWachi
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Post by KachiWachi »

I would guess that the CPU would first look for the data in it's L1 cache. If the data is not there, it would then move on to it's L2 cache. If it is not found there, off we go to the Motherboard cache...and finally system RAM.

Again, I mention cache lines, since the K6+ would have either 128K or 256K, and the Motherboard could have up to 1MB (as you mention).

Even though the cacheable area is the same, the amount of cache lines would be different. If, for whatever reason, the required data from CPU L2 had been flushed, it *may* not have been from the Motherboard cache (due to more lines being available). So data retrieval from there would still be faster than fetching the required data from system RAM.

Cache strategy will also play a role in this...whether Direct Mapped, Associative, or N-Way.

Will it affect system performance? Only testing of your system can tell you that for sure.
DasMan2

Post by DasMan2 »

KachiWachi wrote:Explanation of the system cache at "The PCGuide" -> http://www.pcguide.com/ref/mbsys/cache/func.htm
I believe this link is a good one for every Socket 7 user to read through when trying to tweak the BIOS or system out.
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