Well, they should run at the relaxed timing 5-5-5-16 just fine.

OK does the voltages matter and read different things on net and got confused and if i have to choose one set, which is better and i can see if can find another set with same timing and voltage etc

The ram with 1.8v is what I would use, that is the standard voltage of DDR2. The ones that require 2.1v to run at 800 would be inferior chips IMHO even though their CAS is lower because they require higher voltage to attain the 800mhz and CAS4 over 800Mhz and CAS5 of the ones at 1.8v. Sorta like overclocked by being over voltaged. The 2.1v may run very stable at 1.8v with 5-5-5-16 timing as dr_st stated but only a good mem test would tell. I would not mix them on same board.

Horun wrote:

The ram with 1.8v is what I would use, that is the standard voltage of DDR2. The ones that require 2.1v to run at 800 would be inferior chips IMHO even though their CAS is lower because they require higher voltage to attain the 800mhz and CAS4 over 800Mhz and CAS5 of the ones at 1.8v. Sorta like overclocked by being over voltaged. The 2.1v may run very stable at 1.8v with 5-5-5-16 timing as dr_st stated but only a good mem test would tell. I would not mix them on same board.

ok safer and better to use the lower voltage ones rather the lower cas ones

Horun wrote:

The ones that require 2.1v to run at 800 would be inferior chips IMHO even though their CAS is lower because they require higher voltage to attain the 800mhz and CAS4 over 800Mhz and CAS5 of the ones at 1.8v.

No, I suspect the extra voltage is just to get the lower timings and the DIMM SPD contains EPP data. To sensibly comment I would need to see the DIMM SPD data.

I had a look and found as below in the SIV save files I have. If yours are similar I expect running all four @ 1.8 volts + 400 MHz will be fine.

1[SPD Summary] <- SIV32X - System Information Viewer V5.43 Beta-04 FATARSE2::argh
2
3SIV32X - BIOSTAR A780X-A2 SPD Summary for 2 DIMMs took 0.000 seconds on \\FATARSE2 - Windows 2K x32 Professional  V5.00  Build 2195  Service Pack 4
4
5SMBus  Total for 2 DIMMs   2GB  Banks   Manufacturer (DRAM)  Part Number       Serial     #  [_]Speed   [Y]Suppress Same
6
70_52   DDR2 SDRAM UDIMM    1GB  1  1Gb  Corsair              CM2X1024-8500C5D  0000-0000         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
8       PC2-6400 (400MHz)                                                           JEDEC  1   270.3MHz  4    4    4    13   16   Ranks 1    1.80
9                                                                                          2   400.0MHz  5    5    5    18   23
10                                                                                  EPP FP  2   533.3MHz  5    4    4    14   21   2T         2.10
110_53   DDR2 SDRAM UDIMM    1GB  1  1Gb  ...                  ...               ...           ...
12
13[  OK ]  [ Copy]   [Windows]  [Machine]  [ DIMMs]  [Sensors]  [Status]   [USB Bus]  [ SPD ]  [Volumes]   [SMB Bus]  [PCI Bus]  [ALL Dev]

1[SPD Summary] <- SIV32X - System Information Viewer V5.43 Beta-04 AMD-64-3500::Dick
2
3SIV32X - ELITEGROUP NFORCE6M-A SPD Summary for 4 DIMMs took 0.000 seconds on \\AMD-64-3500 - Windows XP Professional  V5.01  Build 2600  Service Pack 3
4
5SMBus  Total for 4 DIMMs   4GB  Banks     Manufacturer (DRAM)  Part Number         Serial     #  [_]Speed   [Y]Suppress Same
6
70_50   DDR2 SDRAM UDIMM    1GB  2  512Mb  Corsair              CM2X1024-6400C5DHX  FFFF-FFFF         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
8       PC2-6400 (400MHz)                                                               JEDEC  1   270.3MHz  4    4    4    13   15   Ranks 2    1.80
9                                                                                              2   400.0MHz  5    5    5    18   22
100_51   DDR2 SDRAM UDIMM    1GB  2  512Mb  ...                  ...                 ...           ...
11
120_52   DDR2 SDRAM UDIMM    1GB  1  1Gb    Micron               8HTF12864AY-800E1   E81A-B097         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
13       PC2-6400 (400MHz)                                                               JEDEC  1   266.7MHz  4    4    4    12   16   Ranks 1    1.80
14                                                                                              2   333.3MHz  5    5    5    15   20
15                                                                                              3   400.0MHz  6    6    6    18   24
160_53   DDR2 SDRAM UDIMM    1GB  1  1Gb    ...                  ...                 E81A-B096     ...
17
18[  OK ]  [ Copy]   [Windows]  [Machine]  [ DIMMs]  [Sensors]  [Status]   [USB Bus]  [ SPD ]  [Volumes]   [SMB Bus]  [PCI Bus]  [ALL Dev]

red-ray wrote:

No, I suspect the extra voltage is just to get the lower timings and the DIMM SPD contains EPP data. To sensibly comment I would […]
Show full quote

Horun wrote:

The ones that require 2.1v to run at 800 would be inferior chips IMHO even though their CAS is lower because they require higher voltage to attain the 800mhz and CAS4 over 800Mhz and CAS5 of the ones at 1.8v.

No, I suspect the extra voltage is just to get the lower timings and the DIMM SPD contains EPP data. To sensibly comment I would need to see the DIMM SPD data.

I had a look and found as below in the SIV save files I have. If yours are similar I expect running all four @ 1.8 volts + 400 MHz will be fine.

Copy code to clipboard

1[SPD Summary] <- SIV32X - System Information Viewer V5.43 Beta-04 FATARSE2::argh
2
3SIV32X - BIOSTAR A780X-A2 SPD Summary for 2 DIMMs took 0.000 seconds on \\FATARSE2 - Windows 2K x32 Professional  V5.00  Build 2195  Service Pack 4
4
5SMBus  Total for 2 DIMMs   2GB  Banks   Manufacturer (DRAM)  Part Number       Serial     #  [_]Speed   [Y]Suppress Same
6
70_52   DDR2 SDRAM UDIMM    1GB  1  1Gb  Corsair              CM2X1024-8500C5D  0000-0000         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
8       PC2-6400 (400MHz)                                                           JEDEC  1   270.3MHz  4    4    4    13   16   Ranks 1    1.80
9                                                                                          2   400.0MHz  5    5    5    18   23
10                                                                                  EPP FP  2   533.3MHz  5    4    4    14   21   2T         2.10
110_53   DDR2 SDRAM UDIMM    1GB  1  1Gb  ...                  ...               ...           ...
12
13[  OK ]  [ Copy]   [Windows]  [Machine]  [ DIMMs]  [Sensors]  [Status]   [USB Bus]  [ SPD ]  [Volumes]   [SMB Bus]  [PCI Bus]  [ALL Dev]

Copy code to clipboard

1[SPD Summary] <- SIV32X - System Information Viewer V5.43 Beta-04 AMD-64-3500::Dick
2
3SIV32X - ELITEGROUP NFORCE6M-A SPD Summary for 4 DIMMs took 0.000 seconds on \\AMD-64-3500 - Windows XP Professional  V5.01  Build 2600  Service Pack 3
4
5SMBus  Total for 4 DIMMs   4GB  Banks     Manufacturer (DRAM)  Part Number         Serial     #  [_]Speed   [Y]Suppress Same
6
70_50   DDR2 SDRAM UDIMM    1GB  2  512Mb  Corsair              CM2X1024-6400C5DHX  FFFF-FFFF         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
8       PC2-6400 (400MHz)                                                               JEDEC  1   270.3MHz  4    4    4    13   15   Ranks 2    1.80
9                                                                                              2   400.0MHz  5    5    5    18   22
100_51   DDR2 SDRAM UDIMM    1GB  2  512Mb  ...                  ...                 ...           ...
11
120_52   DDR2 SDRAM UDIMM    1GB  1  1Gb    Micron               8HTF12864AY-800E1   E81A-B097         Clock  tCL  tRCD tRP  tRAS tRC  |G|CRC    Volts
13       PC2-6400 (400MHz)                                                               JEDEC  1   266.7MHz  4    4    4    12   16   Ranks 1    1.80
14                                                                                              2   333.3MHz  5    5    5    15   20
15                                                                                              3   400.0MHz  6    6    6    18   24
160_53   DDR2 SDRAM UDIMM    1GB  1  1Gb    ...                  ...                 E81A-B096     ...
17
18[  OK ]  [ Copy]   [Windows]  [Machine]  [ DIMMs]  [Sensors]  [Status]   [USB Bus]  [ SPD ]  [Volumes]   [SMB Bus]  [PCI Bus]  [ALL Dev]

how do i that

Robhalfordfan wrote:

how do i that

It depends on which OS the system is running, if it's running Windows NT, 2K, XP or later then you could download the SIV32L.zip that's attached to SIV support for 386/486/586 class + Alpha CPUs and 3dfx + S3 + SiS + Matrox + XGI + old ATI + NVidia GPUs - Testing Help, extract the files, run SIV32L.exe then press the [ SPD ] button and post a screen shot similar to as below. You could either do this twice, once for each pair of DIMMs or assume all four will be OK @ 1.8 volts and install all four.

If the system is running Windows 9X then you will need to use such as CPUZ or HWiNFO.

800MHz CL5.5.5.18 at 1,8V USUALLY means 800MHz CL4.4.4.12 at ~2,1V. Usually, ie. memory should OC to that (OC'ing margins for DDR2).

Since Intel boards don't support EPP [nVidia thing only], you don't have to worry about wrong voltage : Board will always use 1,8V for Auto setting from jEDEC profile (unless BIOS is bugged).
2,1V have to be set manually in BIOS by You (and the same goes for timings).

You shouldn't have issues pairing those together.
Keep in mind, using 4 sticks usually limits OC, and 2,1V (if Airflow isn't good enough) voltage may cause excessive heating on two middle sticks.

agent_x007 wrote:

Since Intel boards don't support EPP [nVidia thing only], you don't have to worry about wrong voltage : Board will always use 1,8V for Auto setting from jEDEC profile (unless BIOS is bugged).
2,1V have to be set manually in BIOS by You (and the same goes for timings).

This statement is incorrect, I used to have an ASUS P5Q PRO Turbo with an Intel chipset and EPP DIMMs and below is another example of one from a SIV save file I have. I don't know how the ASUS P5Q Deluxe was setup, but the P5Q PRO Turbo specifies EPP in the QVL and I did not setup the timings manually.

Further as neither the motherboard or CPU has been specified I can't see how you can assume it is Intel.

Notice how the current memory timings are the EPP timings.

Background : EPP = Enhanced Performance Profiles
And it's nVidia's version of XMP (before XMP was a thing), it became a thing in later DDR2 memory.
"EPP" is a PROFILE in SPD, and I meant it as such.
Memory support is beyond that, since ALL RAM must have a basic JEDEC profile regardless of EPP, and JEDEC MUST work.
QVL list doesn't mean you have "XMP" or "EPP" option in BIOS to preset everything for you.
It only shows what memory was tested with motherboard and if it worked.

So, two questions :
1) Do you have a "EPP Enable" option in BIOS or did you have to set everything manually (based on values from EPP profile) ?

^Here's example from DDR3 nVidia board.

2) Which profile will BIOS use when there are two mixed EPP enabled memory sets installed ?
^Here's difficult question I don't have an answer to (I never tried it myself 😉)

agent_x007 wrote:

Background : EPP is nVidia's version of XMP (before XMP was a thing). QVL list doesn't mean you have "XMP" or "EPP" option in BI […]
Show full quote

Background : EPP is nVidia's version of XMP (before XMP was a thing). QVL list doesn't mean you have "XMP" or "EPP" option in BIOS to check for memory to work. It only shows what memory was tested with motherboard.

So, two questions :
1) Do you have a "EPP Enable" option in BIOS or did you have to set everything manually ?
2) Which profile will BIOS use when there are two mixed EPP enabled memory sets installed ?

Incorrect again, EPP is DDR2, XMP 1.n DDR3 and XMP 2.n DDR4.

So, two questions :
1) Given I specified "I used to have an ASUS P5Q PRO Turbo" how do you expect me to check what it's BIOS setting are?
2) How do you know which motherboard/chipset and CPU are being used?

What do you mean "incorrect" ?
EPP was predesessor of XMP, it did for DDR2 what XMP does for DDR3.
Hence I wrote EPP was earlier version of XMP.

1) You don't remember what you did to set memory up on Your board ?
OK, but you can't blame me for not knowing it (I'm not in Your head).

2) Why do I have to know which is used ?
Most popular ones are Intel and VIA, nForce is minority.
Intel and VIA don't support EPP, so you have to manually set everything in BIOS.
I wrote about nV earlier.
Again EPP is a PROFILE, NOT a memory type or model.

red-ray wrote:

I used to have an ASUS P5Q PRO Turbo with an Intel chipset and EPP DIMMs

red-ray wrote:

I did not setup the timings manually.

agent_x007 wrote:

What do you mean "incorrect" ?
1) You don't remember what you did to set memory up on Your board ? OK, but you can't blame me for not knowing it (I'm not in Your head).
Again EPP is a PROFILE, NOT a memory type or model.

When you don't know what a word means then I suggest you Google for it's meaning and from doing that you should find https://dictionary.cambridge.org/dictionary/e … glish/incorrect

I further suggest you should read what I specified as you clearly failed to do this given what I quoted above.

Telling me "EPP is a PROFILE" is comparable to telling chickens how to lay eggs.

I don't see how any of what you has said will help Robhalfordfan to fully understand what is possible and I am at a loss as to why you posted as you did.

Robhalfordfan: I suggest you ignore most of what agent_x007 posted as he is talking in general terms and has no way to know which motherboard/chipset and CPU you have.

I think you are overreacting if you say OP should ignore all I wrote just because you don't agree wih something I wrote. Also I read what you wrote, and I wanted to know if your board had "EPP Enable" option from example provided on earlier screenshot.

PS. What OP needed to know is in my first post in this topic.

agent_x007 wrote:

PS. What OP needed to know is in my first post in this topic.

No, OP needs to provide details of the SPD so a decision can be made based on appropriate data rather than relying on your guesses being correct.

I also feel you should do as I did and provide screen shots to justify your statements.

You want me to buy OPs memory, OC it as I wrote in my post and post screenshots ?
Because I'm pretty sure every other screenshot I post will just get "shot down" as "using not correct memory".

agent_x007 wrote:

You want me to buy OPs memory, OC it as I wrote in my post and post screenshots ?
Because I'm pretty sure every other screenshot I post will just get "shot down" as "using not correct memory".

As to how you justify your statements is up to you, all I specified is that I feel you need to justify them.

Further given OP specified ok safer and better to use the lower voltage ones rather the lower cas ones I suspect he does not wish to overclock his DIMMs.

I have an ASUS P5Q PRO (Intel P45) and DDR2 RAM which has an EPP profile for 1066MHz (see attached image). I can confirm that when RAM frequency is set to DDR2-1066 in the BIOS (this is determined using one of possible FSB:DRAM dividers), it reads the correct SPD timing values automatically.

Dunno what it would do if there was both an EPP and a JEDEC profile for the same frequency.

dr_st wrote:

it reads the correct SPD timing values automatically.

Thank you for this which confirms what I recall used to happen on my ASUS P5Q PRO Turbo before the DIMMs with the EPP profile failed.

As for mixing DIMMs then I expect if will all depend on what the SPD is for them and there will be no general answer.