Memory bottleneck

[jay75]

SiSoftware Sandra shows me a bottleneck woth my DDR400 ram.

the cpu bus speed is 4x 133mhz=533mhz=4.28GB/s bandwidth
the ram speed is 2x 133mhz=266mhz=2.14GB/s bandwidth

normally DDR400 ram is about 3.2GB/s bandwidth.

is this just a case of asking for better memory? in which case what should i specify? 4x 133 speed to perfectly match the 533mhz of the cpu?

here is the info from sandra:
====================================================
< Chipset 1 >
Model: Giga-Byte Technology VT8751 ProSavageDDR
P4M266 System Controller
Front Side Bus Speed: 4x 134MHz (536MHz data rate)
Width: 64-bit
Maximum Bus Bandwidth: 4288MB/s (estimated)

< Logical/Chipset 1 Memory Banks >
Bank 0: 512MB DDR-SDRAM 2.0-2-2-7CL 2CMD
Bank Interleave: 4-way
Speed: 2x 134MHz (268MHz data rate)
Width: 64-bit
Maximum Memory Bus Bandwidth: 2144MB/s (estimated)

< Performance Tips >
Notice 5406: System bandwidth appears memory limited.
Attempt to use higher-performance memory.
=====================================================

additonal info:
======================================================
< Benchmark Results >
RAM Bandwidth Int Buff'd iSSE2:1981MB/s
RAM Bandwidth Float Buff'd iSS:1995MB/s

< Int Buff'd iSSE2 (Integer STREAM) Results Breakdown >
Assignment: 1986MB/s
Scaling: 1984MB/s
Addition: 1980MB/s
Triad: 1976MB/s
Data Item Size: 16-bytes
Buffering Used: Yes
Offset Displacement Used: Yes
Bandwidth Efficiency: 92% (estimated)

< Float Buff'd iSSE2 (Float STREAM) Results Breakdown >
Assignment: 2000MB/s
Scaling: 1997MB/s
Addition: 1993MB/s
Triad: 1992MB/s
Data Item Size: 16-bytes
Buffering Used: Yes
Offset Displacement Used: Yes
Bandwidth Efficiency: 93% (estimated)
===================================================

< Processor >
Model: 1x Intel(R) Pentium(R) 4 CPU 2.40GHz
Speed: 2.41GHz
Performance Rating: PR2653 (estimated)
Type: Standard
L2 On-board Cache: 1024kB ECC Synchronous ATC (8-way sectored,
64 byte line size)

< Mainboard >
Bus(es): AGP PCI IMB USB i2c/SMBus
MP Support: 2 CPU(s)
MP APIC: Yes
System BIOS: Award Software International, Inc. F2
Mainboard: P4M266A-8235
Total Memory: 511MB DDR-SDRAM
====================================================

note: it says mobo support for 2 cpu's but it is not a dual mobo. i guess thats a question for another time.

 

[VirtualLarry]

Originally posted by: jay75
SiSoftware Sandra shows me a bottleneck woth my DDR400 ram.

the cpu bus speed is 4x 133mhz=533mhz=4.28GB/s bandwidth
the ram speed is 2x 133mhz=266mhz=2.14GB/s bandwidth

normally DDR400 ram is about 3.2GB/s bandwidth.

Yes, when running at a 200Mhz FSB speed. Your system is clearly running at a 133Mhz FSB speed. That's a pretty big difference.

Originally posted by: jay75
is this just a case of asking for better memory? in which case what should i specify? 4x 133 speed to perfectly match the 533mhz of the cpu?

here is the info from sandra:
Model: Giga-Byte Technology VT8751 ProSavageDDR
P4M266 System Controller
Front Side Bus Speed: 4x 134MHz (536MHz data rate)
Width: 64-bit
Maximum Bus Bandwidth: 4288MB/s (estimated)

note: it says mobo support for 2 cpu's but it is not a dual mobo. i guess thats a question for another time.

Well, there's two theoretical ways to "solve" this problem, but I don't think that you can, given the limitations of that chipset.

One way is because the P4 operates using a quad-data-rate bus, while normal DDR operates using a dual-data-rate bus. So most modern P4 chipsets support "dual-channel" memory, which operates two sets of dual-data-rate, for an effective quad-data-rate, which perfectly matches with the P4's bus date-rate too.

Another way is to run the memory FSB seperately from the CPU FSB. I don't know if your chipset or mobo supports this. Given its age, I highly doubt it. Check your BIOS setup for independent memory clock speed options or frequency ratios. If you can run the CPU at 133Mhz (x 4), and the RAM at 200Mhz (x 2), then you will gain some memory bandwidth, at the expense of the minor latency encountered due to the async CPU/RAM FSB speeds and the internal buffering needed in that case.

My KT400 chipset (for AMD CPU) offers the option of running the RAM at 200Mhz, while running the CPU at 166Mhz, but for overall system efficiency, it is better to run them at the same speed, in this case 166Mhz. That is in fact what your current system is doing as well. Honestly, I wouldn't worry about it, unless you want to spend more money for a new P4 mobo with dual-channel memory. Since your P4 CPU only has a 133Mhz FSB instead of a 200Mhz, the gain would probably not be that noticable anyways.