PowerPC 970 vs 970FX [Archive]

View Full Version : PowerPC 970 vs 970FX

gekko513

Jun 25, 2004, 10:24 AM

I thought the 970FX was just a shrinked 970, but geek.com (http://www.geek.com/procspec/ibm/power4desktop.htm) says the level 1 instruction cache has been upped from 32KB to 64KB.

Why did they choose to increase just the instruction cache? Does anyone know how much this affects the performance?

crazzyeddie

Jun 25, 2004, 11:11 AM

Instruction cache is used to store the instructions used by the CPU. There will probably be no difference in speed (measurable anyway) by this increase. The Data L1 cache is the part of L1 cache that when increased can yield HUGE increases in speed due to its very very fast speed and location on the CPU. However, the L1 cache on most processors is not usually more than 32kb-64kb because it is very expensive. This is one of the main reasons that the Celeron processor (Intel) is so much slower (and cheaper) than even the Pentium 3-- it has very little L1 and/or L2 cache.

gekko513

Jun 25, 2004, 11:56 AM

Instruction cache is used to store the instructions used by the CPU. There will probably be no difference in speed (measurable anyway) by this increase.
If there's no measurable difference in speed, then why did they increase it when it's so expensive?

mgargan1

Jun 26, 2004, 12:58 AM

Sun Baked

Jun 26, 2004, 01:26 AM

geek.com made a mistake, the 970 and 970fx have the same amount of cache... the only difference is die size, the fact that the fx is built on a 300mm wafer, and it 90nm vs 130nm... plus the fx has strained silicon, SOI, and copper interconnects... the 970 doesn't have Strained silicon...maybe geek.com should read the IBM documents again...

But they can't since IBM locked the link that took you to quite a few of the documents.

http://forums.macrumors.com/attachment.php?attachmentid=11081

ddtlm

Jun 26, 2004, 02:05 AM

Mmmm, 12.3W at 1.4ghz.

zimv20

Jun 26, 2004, 02:41 AM

Mmmm, 12.3W at 1.4ghz.
mmmm... laptop-y....