can you run a AMD socket A chip w/ 400fsb along with PC 2100 ram?

[ty1er]

obviously it would be best to runn a 400fsb CPU along with PC3200 ram.

are there any benchmarks out there showing the differences between a 400FSB CPU runing with PC 2100 and PC3200 ram?

thanks.

 

[ts3433]

You really don't want to run asynchronously with an AXP if possible; it actually makes a difference, unlike on an A64.

 

[TheInvincibleMustard]

ts3433's got it right -- on the AXP setup, running your RAM and CPU synchronously will provide better performance. I don't have any benchmarks aside from anecdotal evidence.

ASUS A7N8X Deluxe 2.0
AMD Athlon XP 2800+ (333MHz FSB, Barton core)
Corsair TwinX1024 LL RAM, 2-2-2-5
ATI Radeon 9800 Pro AIW 128MB

Sure, I could run my RAM at PC3200 speeds (and the 2.0 board won't have a problem with that at all), but my overall performance will actually be slightly *lower* than if I keep it at PC2700. It works the opposite way (say if I had a 400MHz FSB CPU and ran my RAM at PC2700) as well, though the performance hit will be greater. Though the 400/333 setup wouldn't be horribly bad, I would certainly postulate that the 400/266 setup would leave your CPU "starving" for memory bandwidth, as information is just not being pushed through fast enough.

Like I said, sorry for no links to benchmarks (I know, "Bad Mustard! Bad! No biscuit!"), as I'm usually the guy with 5+ links in his posts, but I'm hoping you can accept anecdotal evidence in place of some real world benchmarks.

 

[Peter]

Whether you can or can't depends on the chipset northbridge you're using. Those from SiS are versatile in that regard and let you run the RAM slower than the CPU bus. VIA's let you run faster RAM, but not slower. Even with a chipset that can, you still depend on the board design and BIOS implementation to actually have that feature. For example, I've seen that ECS L7S7A2 offers many ratios from 1:2 all the way down to 2:1, so you could even run PC1600 RAM with a 200 MHz* FSB processor there.

*real MHz, not marketing-bull-doubled.

The others are perfectly right that on a north bridge centric architecture, you're best off running the CPU and RAM busses at the exact same speed.

 

[ChineseDemocracyGNR]

I was running DDR333 @ DDR333 with FSB400 on my VIA KT600 board. Performance is about the same as DDR333/FSB333 (I ran tests with an unlocked Mobile).

 

[Peter]

Aha, so the KT600 finally added that capability?