内存设置与内存性能关系的探究

对于一个典型的主板BIOS设置程序来看,基本上都提供了关于内存延迟方面的设置,而这个设置在一定程度上会影响到整个系统的内存性能,当然也可以影响到系统的整体效率。从理论上来看内存延迟的时间越短,那么就越容易完全发挥内存的性能,但是很多用户并不知道如何来设置内存选项才是最合适的,并且也并不知道哪种设置是相对稳定的,今天我们就一起来试验一下,我们使用PC2700 DDR内存几乎吧所有内存设置都测试了一遍,并且做出了一定的分析,最后给出一定的结果,希望可以给大家带来帮助。

测试方法:

主板我们使用了Soyo(梅捷)的SY-P4X400主板,这种主板的BIOS中具有丰富的内存设置选项,所有选现大概有10种以上。测试的软件主要使用了Sisoft Sandra的内存测试项来进行测试,软件版本为2003 v9.41(SP1)。当然这种测试也存在测试误差,因此我们基本上把每种测试都运行几次,然后取平均值。

从BIOS的的选项来看,我们一共可以提供4,608种不同的测试,但这种测试是在是太耗费时间和精力了,因此我们把一些平时很少使用的内存设置项剔除掉,最终得到289种不同的设置模式。

从实际的选项来看我们主要分别调节了内存的速度(100, 133, 166), CAS延迟(3.0, 2.5, 2.0, 1.5),Bank Interleave(关闭,2 Bank,4 Bank)这些主要的内存设置项,同时也测试了一些很少用的设置:(Trp,Tras,Trcd,DRAM Command Rate,DRAM Burst Length,Write Recovery Time,以及DRAM Access Time)。

由于对于内存来说Trp速度一般都是设置在2T上的,但3T有的时候也会有人设置,最终我们给出了36组3T下的结果,另外还有252组数据给予Trp=2T设置下的。

测试内存:

测试的时候我们选择了Crucial两条128MB PC2700内存,这种内存的详细规格是:

模块容量:128MB
封装:184线 DIMM
特点:DDR PC2700
配置:16M x 64
DIMM类型:Unbuffered
ECC:
速度:6ns
电压:2.5V
延迟:CL=2.5

注意,我们测试的公正性,实际使用内存的时候我们并没有增加电压来提供更高的内存稳定性。

测试配置:

Intel P4 2.4Ghz处理器,400Mhz FSB, 512K L2 Cache
Soyo SY-P4X400 Dragon Ultra Platinum主板
ATi Radeon AIW显示卡
Crucial 256 MB PC2700 DDR内存 **
** Maxtor DiamondMax Plus 60GB D740X硬盘
Windows XP Professional Service Pack 1操作系统

测试结果:

FSBCASInterleavetRPtRAStRCDDRCDBLtWRDATIntFloat其它
1003Disabled373243313331332
1002.5Disabled373243313291328
1002Disabled373243313331333
1001.5Disabled373243313311332
10032 Bank373243313881384
10034 Bank373243314421443
1002.52 Bank373243313861384
1002.54 Bank373243314461445
10022 Bank373243313921389
10024 Bank373243314481446
1001.52 Bank373243313881387
1001.54 Bank373243314471446
1003Disabled273243313411339
10032 Bank273243313951393
10034 Bank273243314481446
1002.5Disabled273243313401339
1002.52 Bank273243313961393
1002.54 Bank273243314471445
1002Disabled273243313421340
10022 Bank273243313991397
10024 Bank273243314521448
1001.5Disabled273243313441342
1001.52 Bank273243314011396
1001.54 Bank273243314481450
1003Disabled263243313411339
10032 Bank263243313961396
10034 Bank263243314491446
1002.5Disabled263243313391339
1002.52 Bank263243313971396
1002.54 Bank263243314481446
1002Disabled263243313461345
10022 Bank263243314001397
10024 Bank263243314511450
1001.5Disabled263243313451344
1001.52 Bank263243313971398
1001.54 Bank263243314531448
1003Disabled262243313601362
10032 Bank262243314091407
10034 Bank262243314531450
1002.5Disabled262243313621359
1002.52 Bank262243314091408
1002.54 Bank262243314531449
1002Disabled262243313641362
10022 Bank262243314121412
10024 Bank262243314561455
1001.5Disabled262243313661366
1001.52 Bank262243314131411
1001.54 Bank262243314551455
1003Disabled262143313891389
10032 Bank262143314311429
10034 Bank262143314681467
1002.5Disabled262143313891387
1002.52 Bank262143314311429
1002.54 Bank262143314681466
1002Disabled262143313921392
10022 Bank262143314341433
10024 Bank263143314691468
1001.5Disabled262143313921389
1001.52 Bank262143314321431
1001.54 Bank262143314591457
1003Disabled262183313911390
10032 Bank262183314311430
10034 Bank262183314681466
1002.5Disabled262183313861386
1002.52 Bank262183314311430
1002.54 Bank262183314651465
1002Disabled262183313921390
10022 Bank262183314321434
10024 Bank263183314681468
1001.5Disabled262183313921391
1001.52 Bank262183314331433
1001.54 Bank262183314711468
1003Disabled262182313921390
10032 Bank262182314301430
10034 Bank262182314661465
1002.5Disabled262182313911389
1002.52 Bank262182314331429
1002.54 Bank262182314681464
1002Disabled262182313941393
10022 Bank262182314361434
10024 Bank263182314691468
1001.5Disabled262182313941393
1001.52 Bank262182314351433
1001.54 Bank262182314751468
1003Disabled262182213911394
10032 Bank262182214351432
10034 Bank262182214701470
1002.5Disabled262182213951394
1002.52 Bank262182214351433
1002.54 Bank262182214711470
1002Disabled262182213961397
10022 Bank262182214361438
10024 Bank263182214741472
1001.5Disabled262182213991399
1001.52 Bank262182214361434
1001.54 Bank262182214731741
1333Disabled373243318171820
1332.5Disabled373243318181820
1332Disabled373243318191823
1331.5Disabled3732433DNPDNP
13332 Bank373243319411943
13334 Bank373243319851987
1332.52 Bank373243319401940
1332.54 Bank373243319861986
13322 Bank373243319441943
13324 Bank373243319901992
1331.52 Bank3732433DNPDNP
1331.54 Bank3732433DNPDNP
1333Disabled273243318361840
13332 Bank273243318971898
13334 Bank273243319641964
1332.5Disabled273243318351838
1332.52 Bank273243318991899
1332.54 Bank273243319611964
1332Disabled273243318381383
13322 Bank273243318971900
13324 Bank273243319671968
1331.5Disabled2732433DNPDNP
1331.52 Bank2732433DNPDNP
1331.54 Bank2732433DNPDNP
1333Disabled263243318371836
13332 Bank263243318991900
13334 Bank263243319631963
1332.5Disabled263243318341838
1332.52 Bank263243319001899
1332.54 Bank263243319861988
1332Disabled263243317781789
13322 Bank263243318811882
13324 Bank263243319891989
1331.5Disabled2632433DNPDNP
1331.52 Bank2632433DNPDNP
1331.54 Bank2632433DNPDNP
1333Disabled262243318591863
13332 Bank262243319131915
13334 Bank262243319711971
1332.5Disabled262243318601862
1332.52 Bank262243319151916
1332.54 Bank262243319691968
1332Disabled262243318621863
13322 Bank262243319171918
13324 Bank262243319711972
1331.5Disabled2622433DNPDNP
1331.52 Bank2622433DNPDNP
1331.54 Bank2622433DNPDNP
1333Disabled262143318861887
13332 Bank262143319371938
13334 Bank262143319831984
1332.5Disabled262143318871890
1332.52 Bank262143319361935
1332.54 Bank262143319861987
1332Disabled262143318901891
13322 Bank262143319401940
13324 Bank263143319841985
1331.5Disabled2621433DNPDNP
1331.52 Bank2621433DNPDNP
1331.54 Bank2621433DNPDNP
1333Disabled262183318891889
13332 Bank262183319361937
13334 Bank262183319871987
1332.5Disabled262183318921895
1332.52 Bank262183319391939
1332.54 Bank262183319871988
1332Disabled262183318951894
13322 Bank262183319431944
13324 Bank263183319891990
1331.5Disabled2621833DNPDNP
1331.52 Bank2621833DNPDNP
1331.54 Bank2621833DNPDNP
1333Disabled262182318951897
13332 Bank262182319391941
13334 Bank262182319881990
1332.5Disabled262182318931897
1332.52 Bank262182319391941
1332.54 Bank262182319871987
1332Disabled262182318971898
13322 Bank262182319441944
13324 Bank263182319891991
1331.5Disabled2621823DNPDNP
1331.52 Bank2621823DNPDNP
1331.54 Bank2621823DNPDNP
1333Disabled262182218971898
13332 Bank262182219441943
13334 Bank262182219911990
1332.5Disabled262182218961898
1332.52 Bank262182219421943
1332.54 Bank262182219911991
1332Disabled262182219001901
13322 Bank262182219451947
13324 Bank263182219921993
1331.5Disabled2621822DNPDNP
1331.52 Bank2621822DNPDNP
1331.54 Bank2621822DNPDNP
1663Disabled373243321482148
1662.5Disabled373243321522154
1662Disabled373243321522152
1661.5Disabled3732433DNPDNP
16632 Bank373243321532154
16634 Bank373243322182218
1662.52 Bank373243322872287
1662.54 Bank373243322172218出错一次
16622 Bank373243322362238
16624 Bank3732433DNFDNF不稳定,可能重新启动,软件出错
1661.52 Bank3732433DNPDNP
1661.54 Bank3732433DNPDNP
1663Disabled273243321702171
16632 Bank273243322282228
16634 Bank273243322862287
1662.5Disabled273243321722170
1662.52 Bank273243322272227
1662.54 Bank273243322882286
1662Disabled273243321702172
16622 Bank273243322302229
16624 Bank273243322892290
1661.5Disabled2732433DNPDNP
1661.52 Bank2732433DNPDNP
1661.54 Bank2732433DNPDNP
1663Disabled263243321732173
16632 Bank263243322282229
16634 Bank263243322882288
1662.5Disabled263243321702171
1662.52 Bank263243322292228
1662.54 Bank263243321372137
1662Disabled263243321712172
16622 Bank263243322302231
16624 Bank263243322892289
1661.5Disabled2632433DNPDNP
1661.52 Bank2632433DNPDNP
1661.54 Bank2632433DNPDNP
1663Disabled262243321932193
16632 Bank262243322432243
16634 Bank262243322932293
1662.5Disabled262243321392160
1662.52 Bank262243322412242
1662.54 Bank262243322922291
1662Disabled262243321932195
16622 Bank262243322452245
16624 Bank2622433DNBDNB
1661.5Disabled2622433DNPDNP
1661.52 Bank2622433DNPDNP
1661.54 Bank2622433DNPDNP
1663Disabled262143322182219
16632 Bank262143322592259
16634 Bank262143322972300
1662.5Disabled262143322182221
1662.52 Bank262143322612258
1662.54 Bank262143323002301
1662Disabled262143322212219
16622 Bank262143322612262出错一次
16624 Bank2631433DNBDNB
1661.5Disabled2621433DNPDNP
1661.52 Bank2621433DNPDNP
1661.54 Bank2621433DNPDNP
1663Disabled262183322202219
16632 Bank262183322592258
16634 Bank262183323022300
1662.5Disabled262183322182220
1662.52 Bank262183322612258
1662.54 Bank262183323012300
1662Disabled262183322202221
16622 Bank2621833DNBDNB
16624 Bank2631833DNBDNB
1661.5Disabled2621833DNPDNP
1661.52 Bank2621833DNPDNP
1661.54 Bank2621833DNPDNP
1663Disabled262182322192216
16632 Bank262182322612258
16634 Bank262182322992300
1662.5Disabled262182322172218
1662.52 Bank262182322602259
1662.54 Bank262182323012301
1662Disabled262182322192221
16622 Bank2621823DNBDNB
16624 Bank2631823DNBDNB
1661.5Disabled2621823DNPDNP
1661.52 Bank2621823DNPDNP
1661.54 Bank2621823DNPDNP
1663Disabled262182222192219
16632 Bank262182222602261
16634 Bank262182223012301
1662.5Disabled262182222212222
1662.52 Bank262182222612260
1662.54 Bank262182223032302
1662Disabled2621822DNFDNFSandra出错
16622 Bank2621822DNBDNB
16624 Bank2631822DNBDNB
1661.5Disabled2621822DNPDNP
1661.52 Bank2621822DNPDNP
1661.54 Bank2621822DNPDNP

解释:

DNP - Did not post(无法通过自检)
DNF - Did not finish(无法完成)
DNB - Did not boot(无法启动)

初步结论:

  • 各种设置下实际内存性能差别不算太大(内存速度调节除外)
  • 从实际的内存带宽来看,最低的速度为1333MB/s,最高速度则为2303MB/s,它们之间相差73%(970MB/sec)

详细分析 :

内存时钟频率:

内存时钟频率是我们平时用的最多的内存设置了,基本上更高的时钟频率可以带来更高的内存效率:

时钟频率:性能提升:增加的效率:%理论增加的效率:%
100 to 133~500 MB/sec35-40%33%
133 to 166~200-300MB/sec10-15%25%
100 to 166~750-800MB/sec55-60%66%

CAS:

CAS Latency(Column Address Strobe Latency行地址控制器延迟)就是内存纵向地址脉冲的反应时间,它的设置直接关系到内存读取数据的延迟,设置数值越小内存的效率越高。一般来说内存可以设置的延迟为2T或者3T,但一些新的主板也提供了1.5T这种选项,那么我们就来看看CAS延迟对内存的影响:

CAS Latency:性能提升:增加的效率:%
3.0 to 2.5~0-2MB/sec0%-0.001%
2.5 to 2.0~0-3MB/sec0%-0.002%
2.0 to 1.5~0-3MB/sec0%-0.002%
3.0 to 2.0
(166MHz 内存工作频率)~0-4MB/sec0%-0.002%
3.0 to 1.5
(100 MHz内存工作频率)~0-4MB/sec0%-0.002%

从测试来看CAS对内存带宽的影响并不大,因此在内存设置中我们并不需要对CAS Latency项太在意。

Bank Interleave:

Bank是内存中一个非常重要的存储单元,对于内存来说寻址的时候行(Row)和列(Column)所制定的范围就是内存的逻辑Bank(Logical BANK),简单的说Bank就是内存同北桥芯片之间数据交换的通道。Bank Interleave则是内存Bank交错的功能,这种功能可以大大提升内存预读取的效率。

Bank Interleave:性能提升:增加的效率:%
Disabled to 2-Way40-50MB/sec1%-4%
2-Way to 4-Way40-50MB/sec1%-4%
Disabled to 4-Way80-100MB/sec2%-8%

从Bank Interleave的设置来看其最高可以提高40-50MB/s的内存带宽,因此这应该算是一个比较影响内存性能的选项了,不过对于不同内存工作频率来说这个提升幅度是不同的,在100Mhz频率下可以提供4%的效率,但是如果频率在166Mhz下,提升的效率仅为1%。

Precharge to Active (tRP):

Precharge to Actives就是内存激活(预充电)的时间, Precharge指令一般用于同一个Bank间的不同的行之间的数据读取。Precharge指令到下一个Active命令之间的时间价格叫做tRP。需要注意的是部分预充电时间同上一次的数据传输时间是有重叠的。随着CAS延迟时间的延长,预充电时间同上次读取操作数据输出的重叠时间就越多。

tRP:性能提升:增加的效率:%
3T to 2T10-20MB/sec.1%

tRP设置其实同内存工作频率有很大关系,当100Mhz外频下其可以提升10MB/s的带宽,而在166Mhz频率下则可以提升20MB/的带宽。

Active to Precharge (tRAS):

Active to Precharge正好同Precharge to Active是一个相反的过程,它的时间也会在一定程度上影响系统性能。

tRAS:性能提升:增加的效率:%
7T to 6T~0-3MB/sec0%-0.001%

不过同tRP相比,它的设置最终对系统性能影响并不大。

Active to CMD (tRCD):

tRCD是RAS到CAS的延迟,其实就是从开始执行Active命令到执行内存实际读取或者写入命令时的时间差。

tRCD:性能提升:增加的效率:%
3T to 2T20-30MB/sec1.0%-1.5%

对于tRCD设置来说,内存工作频率越高其效率也会有一定提升,因此在使用高频内存的时候tRCD可以设置相对较高的项。

DRAM Command Rate(self-abbreviated DRC):

DRC:性能提升:增加的效率:%
2T to 1T~30MB/sec1.1%-2.1%

DRAM Command Rate设置对内存性能影响比较大,无论在何种内存模式下把速度设置为1T都可以提升30MB/s左右的内存带宽。

DRAM Burst Length (self-abbreviated DBL):

DRAM爆发传输一般对于连续的数据存取有一定的影响,但是实际上来看这种设置实际的提升效率并不高。

DBL:性能提升: <TD align=mid
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