Q: XP vs. L2 & L3 cache ?

  • Thread starter Thread starter Mr. X
  • Start date Start date
M

Mr. X

Hi.

One of my PCs is an oldie and I want to squeeze the most processing
power out of it:

Mobo: ASUS TX-97_XE
CPU: AMD K6-3/400 MHz (FSB @ 66.6 MHz)
RAM: 256M

The AMD has L1 and L2 cache, as follows:

Internal split, 64K L1 Cache
- 32K instruction cache + 20K predecode cache
- 32K writeback dual-ported data cache

Internal full-speed, 256K L2 cache
- Four-way set associative


Mobo has extra 512K SRAM on-board Pipelined Burst Cache

So as I understand it, the extra cache of the mobo counts as L3-level
cache.


My question is:

The following registry value specifies how many bytes L2 cache the CPU
has (*). Currently set to 262144 decimal (256 * 1024).

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory
Management\SecondLevelDataCache

(*) Yes, XP is supposed to autodetect it, but I prefer to be explicit
about it.


So what about L3 cache then?

a) Is it automatically detected and used if present?
b) How much does it impact system performance? (if at all)
c) Is there a hidden "TertiaryLevelDataCache" value I could set in the
registry?


Any feedback greatly appreciated. Thanks.
Mark T.
 
I think L3 cache is only on later motherboards

I think some of the new 64 bit motherboards
have L3 cache onboard. And I dont think
you can tweak the registry to get it (I maybe wrong).
 
The new Intel processors have the L3 located on the die:
The 2MB L3 Cache is available with only the Pentium 4 processor Extreme
Edition at 3.20 GHz. The additional third level of cache is located on the
processor die and is designed specifically to meet the compute needs of
high-end gamers and other power users. The Integrated Level 3 Cache is
available in 2MB and is coupled with the 800 MHz system bus to provide a
high bandwidth path to memory. The efficient design of the integrated Level
3 cache provides a faster path to large data sets stored in cache on the
processor. This results in reduced average memory latency and increased
throughput for larger workloads.
 
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