XPS8500 memory latency requirements

Crucial is offering 2x8GB modules for the XPS 8500 (1333 MHz) with CL 9 here, if that's of any help.

I have 2 xps 8500 they both have 12gb of ddr3 pc2-12800 (1600mhz) memory  (2x4gb)= 8gb plus (2x2gb)=4gb total of 12gb  both machines have the same (2gbx2) sticks they are samsung 2gb 1rx8 pc3-12800u-11-11-A1   M338B5773DH0-CK0   One has (2x4gb) of nanya  NT4GC64B8HG0NF-D-1 PC-12800u the other has Micron  MT16JTF51264AZ-1G6M1  PC3- 12800U 11-11-B1  These 4gb and 2gb  sticks have a CL of 11 . I also was looking for 8gbx2 but havent found any available.  the only 12800 (1600mhz) memory 8gb sticks  that I found were the  enhanched XMP type  and I dont know if this style is comapatable with the xps 8500 . crucial sell ddr3 pc3-10600 (1333mhz) 8gb sticks that they say are compatible    hope this helps you ..I am still looking for the 8gb ddr3 pc3-12800 (1600mhz) sticks It seems that most mfgers make the 2gb and the 4gb but 8gb insnt available

I have found memory  2x8GB in dual mode, DDR3 1600 non-ECC, CL11 1.5v, form

1. Corsair CMX16GX3M2A1600C11

2. PATRIOT PSD38G1600KH  $112.00

3.  Adata  ae3u1600w88g11-drh  $100.00

4. AMD  AE316G1601U2K- $149.00

I have not tried any of them, and I will call the mfgrs tomorrow to see if they might work. I may order from Newegg, who allows 30 day return on memory. I was not aware of XMP type, and will check further, but , as you know Dell says it will offer 8x2 for 32GB. I wonder if Dell is not selling 32 yet  due to lack of sufficient supplies, not lack of availability.

I wonder if Dell is not selling 32 yet  due to lack of sufficient supplies, not lack of availability.

I bet the reason is simple: COST

I just called Newegg and explained how Corsair misled me, and they agreed to a full refund! What a great company Newegg is!

I recently purchased an XPS8500. It has a total of 8GB of memory (2x4GB). It too has the Micron sticks in it. Here is the data sheet.

http://www.micron.com/~/media/Documents/Products/Data%20Sheet/Modules/jtf16c256_512_1gx64az.pdf

It looks like it is available in 8GB sticks (from the data sheet).

MT16JTF1G64AZ-1G6M1

If you can't source that specific part, you could find one with identical specs.

BTW, if you look at that Micron data sheet, you will see that PC3-12800 (CL = 10 and CL = 9) will have a clock speed of 1333MHz.

From the data sheet, it looks like a CL less than 11 will cause the clock to default to a lower speed.

I'm not entirely sure how these DIMMs work, but I think the SPD on the memory stick is telling the motherboard what clock speed to use, (depending on the CL value).

On some motherboards you can set the memory bus speed in the BIOS. Apparently you can't do this with this motherboard.

On this Dell motherboard it looks like the memory stick controls the bus speed. So be careful what you use, ha ha.

I looked around for that Micron 8GB stick. It looks pretty pricey. The best thing is for someone to find an alternate part. I recommend you look at the subject data sheet first before buying though.

Interesting how the clock speed is decreased to get a lower latency cycle. hah ha

I guess you can't have it both ways. This is not a motherboard for overclocking.

I looked at some other memory sticks available from other manufacturers. Regrettably most don't seem to have data sheets on their products. Maybe the only way to determine what will work is for different folks to dive right in and try what's out there. Hopefully they'll post their results.

Hmmm, I sorta read through JEDEC Standard No. 79-3E which is the DDR3 spec. As far as I can tell the memory stick doesn't control the clock speed.

It has the CAS Latency (CL) value programmed into Mode Register 0 (MR0). (See paragraph 3.4.2.2.) The spec also defines the timing for DDR3 CAS values other than CL = 11.

From what I can infer from this is that the Dell motherboard reads MR0. Depending on the value it sets the memory bus speed accordingly. I would have to further read the Intel chipset spec to see what is going on.

On some motherboards the memory bus speed can be set to auto or manual in the BIOS. I would assume the CAS value is ignored when in the manual mode.

From what I can conclude so far is that memory sticks with CL = 11 will set the clock speed to 1600MHz. That speed probably provides reliable performance at CL = 11.

With a lower CL however, the motherboard will also reduce the clock speed accordingly. To provide reliable performance I would assume.

You can use a freeware program (HWiNFO64) to analyze your memory. Here are the results for the 4GB micron stick inside my XPS8500.

General Module Information                                                      

Module Size:                                                                    4096 MBytes

Memory Type:                                                                   DDR3 SDRAM

Module Type:                                                                    Unbuffered DIMM (UDIMM)

Memory Speed:                                                                800.0 MHz (PC3-12800)

Module Manufacturer:                                                      Micron Tech.

Module Part Number:                                                      16JTF51264AZ-1G6M1

Module Revision:                                                              12621

Current Timing (tCAS-tRCD-tRP-tRAS):                                            11.0-11-11-28

Supported Module Timing at 800.0 MHz:                                           11-11-11-28

Supported Module Timing at 666.7 MHz:                                           9-9-9-24

Supported Module Timing at 533.3 MHz:                                           7-7-7-19

Supported Module Timing at 400.0 MHz:                                           6-6-6-14

Supported Module Timing at 333.3 MHz:                                           5-5-5-12

It looks like a memory stick with 11-11-11-28 timing will run at 1600MHz.

Or at least this Micron stick does.

thanks Atomsite for all your research concerning xps 8500 memory.. the only think I can say is... its been a learning experience trying to purchase memory for a dell xps 8500 to say the least. Presently I have 2 xps 8500  I-7 ,Hd 7870 video ,32 gb mem, win 7 pro 64 bit ,2tb/256ssd Hd . bios A06.. about 3 weeks ago I was finally able to purchase   two  32gb kits from dell for both machines  .   Very priceeeee  approx $111.00 per 8gb stick the Dell P/N is A5764358 (1x8gb)   mfg P/N SNP66GKYC/8G  stickers on actual memory indicate that this memory in reality is Samsung   M378B1G73BHO--CKO  (8gb)  Lat  CL11 , 1.5v  I guess thats one disatvantage of buying a computer with proprietary parts (MB)  Last week I noticed that crucial site now list a 16 gb kit  P/N  CT3329246  @ $159.99 which is 1.35 v  oh well could have saved a $100.00/per 32gb kit if I had waited   so far so good now onto next upgrade I want to install a second Hd  sata III for  back up ....looks like this will be a problem tooo...I see from other posts concerning the  xps 8500 that it seems that the pcle slots do not reconize sata III cards  can't see running the hd's @ sata II speeds ...after all this (xps 8500 is supposed to be a performance machine)  stay tuned .... I only wish that dell would work  out all the BUGS prior to distribution (sales) ..I hate being a guinea pig    Thanks again for all insights and efforts      Mac