DDR3 continues the evolution in memory technology and provides several improvements to the exsisting DDR2 architecture. The primary benefit is an increase of the I/O bus to operate at 4 times the speed of the memory cell it contains. DDR3 also allows for chip capacities from 512 MB to 8 GB. This ability in effect allows for memory modules of up to 16 GB in size.
Desktop Memory Module
Portable Memory Module
CAUTION: Memory slots on system boards that support DDR3 are keyed to ONLY accept DDR3 modules. DDR2 will not fit into a DDR3 slot and DDR3 will not fit into a DDR2 slot.
DDR3 Enhancements
Higher speeds — DDR3 provides higher memory transfer rates. Current industry specifications call for transfer rates of 800, 1066, 1333 and 1600 megahertz. Actual transfer rates may differ depending on the system's front side bus speed.
Doubled "Pre fetch Buffer" — DDR3 doubles the pre-fetch buffer from 4 bits to 8 bits. In other words, DDR3 technology doubles the width of the internal bus between the actual DRAM core and the input/output buffer. As a result, the increase in the data transfer rate provided by DDR3 doesn't require faster operation of the memory core. Only external buffers start working faster.
On-Module termination — This introduces some improvements over DDR2 for the DDR3 signal protocol, since the memory bus frequency has increased significantly. DDR3 uses fly-by topology with on-module signal termination to transfer addresses, management and stabilization commands. It means that the signals are sent to all chips of the memory modules one by one, and not altogether at the same time. This allows for more efficient data flow, storage, and retrieval.
Read/Write leveling — As a result of the On-Module Termination improvement, the data read/write algorithms have also changed. DDR3 controllers now have to successfully recognize and process time shifts on data receipt from the chips generated by fly-by architecture used for commands transfer. This technique is known as read/write leveling.
Reduced voltage requirement — Like previous semiconductor processes, the voltage technology for DDR3 has been scaled down from 1.8 V (DDR2) to 1.5 V. This results in a power savings of almost 30%.
Implementation Challenges
Along with the improvements above, there are a few drawbacks to DDR3 technology:
Increased CAS Latency — CAS (column address strobe) Latency is the time (in number of clock cycles) that elapses between the memory controller telling the memory module to access a particular column in the current row, and the data from that column being read from the module's output pins.
Overall cost — Currently, this technology costs more than its DDR2 predecessor.
Memory Configuration
DDR memory can run in dual-channel mode, which allows the system to have twice the memory bandwidth using the same memory technology.
Dual-Channel Configurations
To achieve dual-channel performance, the total memory in each channel must be the same. If the channels do not match or if the system has only one DIMM installed, the system memory operates in single-channel mode or in dual channel asymetrical mode. The system works normally in single-channel mode, but the user loses the benefit of increased memory throughput.
Dual-channel mode is always present when both memory channels are populated. However, for optimum dual-channel performance, the size of the modules must match.
Memory Channels
Channel A
Channel B
BIOS Says
Performance
DIMM
No DIMM
Single Channel
Single channel
DIMM
Same as channel A
Dual Channel Interleaved
Dual channel interleaved
DIMM
Same as channel A except speed
Dual Channel Interleaved (in lowest DIMM speed)
Dual channel interleaved (in lowest DIMM speed)
DIMM
Same as channel A except density
Dual Channel Interleaved
Dual channel interleaved
DIMM
Same as channel A except size
Dual Channel Asymmetric
Single channel
No DIMM
DIMM
Single Channel
Single channel
Basically, when both DIMM connectors are populated, the system has optimum dual-channel performance unless channels A and B have different amounts of memory.
Memory Speeds
Some confusion has been created due to the difference in the actual listings for speed ("MHz") and the way memory is described from a sales standpoint ("PC XXXXXX"). The listings below should resolve any confusion.
PC3-6400 = 800 MHz
PC3-8500 = 1066 MHz
PC3-10666 = 1333 MHz
PC3-12800 = 1600 MHz
Troubleshooting
Memory errors on the system display the new ON-FLASH-FLASH or ON-FLASH-ON failure code. If all memory fails, the LCD does not turn on. Troubleshoot for possible memory failure by trying known good memory modules in the memory connectors on the bottom of the system as well as under the keyboard. As always, follow the instructions in DSN and perform all steps suggested to verify the problem. 4 GB Memory Barrier The Windows® XP release as well as 32-bit versions of Windows Vista can only use a maximum of 4 GB of address space. However, the amount of memory available to the operating system is less than 4 GB. Certain components within the computer require memory address space in the 4 GB range. Any memory address space reserved for these components cannot be used by the operating system.
NOTE: This is a limitation of a 32-bit architecture: the system can only address 4 GB of allocated memory. Allocated memory is made up of physical RAM and any I/O space needed by devices. Normally this is not a problem, but when a system has 4 GB of physical memory, the memory addresses needed to map RAM overlap the space needed for the I/O devices. In this case the need for I/O space takes precedence, and the amount of RAM visible to the operating system is limited to 4 GB minus the I/O allocation.
Ram Speed is determined by the SPD and the CPU FSB. The linked ram is guaranteed to work with the 780.
Issues arise when you try to use ECC or Quad Rank or Buffered or HIGH Density ram. The issue is that it DOES NOT WORK AT ALL. GSKill Ram has this issue for example.
Various Bios can handle faster Ram but not ECC, Buffering, Density, and Some Vendors.
Hello my friend ..
germany here ..
I bought a super small Optiplex 780 used.
He is equipped with exactly this RAM (2x 4 GB) your link show.
But .... the BIOS and Win7 system info, show me 2x2GB
Did my previous owner get fouled with his 4 GB of RAM, or is the small DELL unable to process 4 GB of bars?
Hello, from Argentine, i also have a Optiplex 780, core 2 duo, and bought a crucial 4 gb ddr3 module Crucial Pc 4gb Ddr3l-1600 Udimm Ct51264bd160b , didn't work. but crucial says 1.35 volts, but Dell uses 1.5 volts ?. Why that difference ?. Thanks !.
Also, by any chance did you mix your Crucial module with other RAM or are all RAM sticks the same?
From the tech guide, I don't know if you know: Memory modules should be installed in pairs of matched memory size, speed, and technology. If the memory modules are not installed in matched pairs, a slight reduction in performance may occur.
Name brands should also match. Dell's can be finicky about that and sometimes other PC's. One of our Rockstars, besides having a Dell laptop, has a homebuilt Asus. It can take 2 different brands of memory separately, but not mixed.
I can not say why the ct51264bd160b does not work in the Dell.
Everything is the way Dell likes it. Non ECC is important. ECC do not work here.
The voltage is also unimportant as long as all RAM are the same. I tested that with both voltages. The board adjusts the voltage for the RAM.
Also the PC12800 processes the Dell. At least Samsung and Kingston.
Can it be that your RAM has a defect?
speedstep
9 Legend
•
47K Posts
0
August 21st, 2018 04:00
The recommended Ram must be LOW Density, Intel Compatible.
http://www.crucial.com/usa/en/optiplex-780-desktop/CT7339271
Specs: DDR3 PC3-12800 • CL=11 • Unbuffered • NON-ECC • DDR3-1600 • 1.35V • 512Meg x 64 •
DELL-Jesse L
Moderator
•
17.9K Posts
0
August 21st, 2018 04:00
CruzKid,
Below are the memory specs and memory configuration information for the OptiPlex 780 sff.
Optiplex 780 Drivers, Downloads and Manuals
Memory
What Is DDR3 Memory?
DDR3 continues the evolution in memory technology and provides several improvements to the exsisting DDR2 architecture. The primary benefit is an increase of the I/O bus to operate at 4 times the speed of the memory cell it contains. DDR3 also allows for chip capacities from 512 MB to 8 GB. This ability in effect allows for memory modules of up to 16 GB in size.
Memory slots on system boards that support DDR3 are keyed to ONLY accept DDR3 modules. DDR2 will not fit into a DDR3 slot and DDR3 will not fit into a DDR2 slot.
DDR3 Enhancements
Implementation Challenges
Along with the improvements above, there are a few drawbacks to DDR3 technology:
Memory Configuration
DDR memory can run in dual-channel mode, which allows the system to have twice the memory bandwidth using the same memory technology.
Dual-Channel Configurations
To achieve dual-channel performance, the total memory in each channel must be the same. If the channels do not match or if the system has only one DIMM installed, the system memory operates in single-channel mode or in dual channel asymetrical mode. The system works normally in single-channel mode, but the user loses the benefit of increased memory throughput.
Dual-channel mode is always present when both memory channels are populated. However, for optimum dual-channel performance, the size of the modules must match.
(in lowest DIMM speed)
(in lowest DIMM speed)
Basically, when both DIMM connectors are populated, the system has optimum dual-channel performance unless channels A and B have different amounts of memory.
Memory Speeds
Some confusion has been created due to the difference in the actual listings for speed ("MHz") and the way memory is described from a sales standpoint ("PC XXXXXX"). The listings below should resolve any confusion.
Troubleshooting
Memory errors on the system display the new ON-FLASH-FLASH or ON-FLASH-ON failure code. If all memory fails, the LCD does not turn on. Troubleshoot for possible memory failure by trying known good memory modules in the memory connectors on the bottom of the system as well as under the keyboard. As always, follow the instructions in DSN and perform all steps suggested to verify the problem. 4 GB Memory Barrier The Windows® XP release as well as 32-bit versions of Windows Vista can only use a maximum of 4 GB of address space. However, the amount of memory available to the operating system is less than 4 GB. Certain components within the computer require memory address space in the 4 GB range. Any memory address space reserved for these components cannot be used by the operating system.
This is a limitation of a 32-bit architecture: the system can only address 4 GB of allocated memory. Allocated memory is made up of physical RAM and any I/O space needed by devices. Normally this is not a problem, but when a system has 4 GB of physical memory, the memory addresses needed to map RAM overlap the space needed for the I/O devices. In this case the need for I/O space takes precedence, and the amount of RAM visible to the operating system is limited to 4 GB minus the I/O allocation.
CruzKid
9 Posts
0
August 21st, 2018 06:00
Are you sure that it supports 1600mhz ram? Because Jesse's post says it supports 1067 and 1333mhz ram
speedstep
9 Legend
•
47K Posts
0
August 21st, 2018 11:00
Ram Speed is determined by the SPD and the CPU FSB. The linked ram is guaranteed to work with the 780.
Issues arise when you try to use ECC or Quad Rank or Buffered or HIGH Density ram. The issue is that it DOES NOT WORK AT ALL. GSKill Ram has this issue for example.
Various Bios can handle faster Ram but not ECC, Buffering, Density, and Some Vendors.
Standard
DRAM cell
Cycle
I/O bus
Data
Module
Peak
Timings
CAS
name
FSB
time
clock
rate
name
Transfer Rate
Wait States
Latency
(MHz)
(ns)
(MHz)
(MT/s)
(MB/s)
(CL-tRCD-tRP)
(ns)
DDR3-800D
100
10
400
800
PC3-6400
6400
5-5-5
12.5
DDR3-800E
100
10
400
800
PC3-6400
6400
6-6-6
15
DDR3-1066E
133.33
7.5
533.33
1066.67
PC3-8500
8533.33
6-6-6
11.25
DDR3-1066F
133.33
7.5
533.33
1066.67
PC3-8500
8533.33
7-7-7
13.125
DDR3-1066G
133.33
7.5
533.33
1066.67
PC3-8500
8533.33
8-8-8
15
DDR3-1333F*
166.67
6
666.67
1333.33
PC3-10600
10666.67
7-7-7
10.5
DDR3-1333G
166.67
6
666.67
1333.33
PC3-10600
10666.67
8-8-8
12
DDR3-1333H
166.67
6
666.67
1333.33
PC3-10600
10666.67
9-9-9
13.5
DDR3-1333J*
166.67
6
666.67
1333.33
PC3-10600
10666.67
10-10-10
15
DDR3-1600G*
200
5
800
1600
PC3-12800
12800
8-8-8
10
DDR3-1600H
200
5
800
1600
PC3-12800
12800
9-9-9
11.25
DDR3-1600J
200
5
800
1600
PC3-12800
12800
10-10-10
12.5
DDR3-1600K
200
5
800
1600
PC3-12800
12800
11-11-11
13.75
DDR3-1866J
233.33
4.286
933.33
1866.67
PC3-14900
14933.33
10-10-10
10.56
DDR3-1866K
233.33
4.286
933.33
1866.67
PC3-14900
14933.33
11-11-11
11.786
DDR3-1866L
233.33
4.286
933.33
1866.67
PC3-14900
14933.33
12-12-12
12.857
DDR3-1866M
233.33
4.286
933.33
1866.67
PC3-14900
14933.33
13-13-13
13.929
DDR3-2133K
266.67
3.75
1066.67
2133.33
PC3-17000
17066.67
11-11-11
10.313
DDR3-2133L
266.67
3.75
1066.67
2133.33
PC3-17000
17066.67
12-12-12
11.25
DDR3-2133M
266.67
3.75
1066.67
2133.33
PC3-17000
17066.67
13-13-13
12.188
DDR3-2133N
266.67
3.75
1066.67
2133.33
PC3-17000
17066.67
14-14-14
13.125
Tom Hofmann
1 Rookie
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10 Posts
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June 6th, 2019 04:00
speedstep
9 Legend
•
47K Posts
0
June 6th, 2019 10:00
There's nothing to explain.
It takes Low Density Ram and USFF only has 2 ram slots.
DDR3 PC3-12800 • CL=11 • UNBUFFERED • NON-ECC • DDR3-1600 • 1.35V • 512MEG X 64 •
So 8 gigs is possible using 4 gig dimms.
16 gigs is possible when you have 4 ram slots. The shared memory is never recovered.
Max Dimm size is 4 gigs.
https://www.crucial.com/usa/en/optiplex-780-small-form-factor/CT7339273
http://i.dell.com/sites/doccontent/business/solutions/engineering-docs/en/Documents/optiplex-780-tech-guide.pdf
speedstep
9 Legend
•
47K Posts
1
June 6th, 2019 10:00
4 GIG modules must be LOW Density.
4 GIGS is maximum Dimm Size.
64 bit OS is required to use more than 4 gigs of ram.
8 or 16 gigs is max depending on how many ram slots 2 or 4 slots.
user_1bc77c
1 Message
1
October 24th, 2019 11:00
Hello, from Argentine, i also have a Optiplex 780, core 2 duo, and bought a crucial 4 gb ddr3 module Crucial Pc 4gb Ddr3l-1600 Udimm Ct51264bd160b , didn't work. but crucial says 1.35 volts, but Dell uses 1.5 volts ?. Why that difference ?. Thanks !.
bradthetechnut
7 Technologist
•
9.4K Posts
0
October 25th, 2019 19:00
Hi @
So hi to either "no name" or "not applicable" as it sometimes appears.
Where did you find that a 780 SFF uses 1.5v RAM? I searched the tech guide and the owner's manual and couldn't find a RAM voltage reference.
Optiplex 780 Tech Guide
bradthetechnut
7 Technologist
•
9.4K Posts
0
October 25th, 2019 21:00
https://www.dell.com/community/Optiplex-Desktops/Optiplex-780-ram-upgrade-problem/td-p/6124691
Also, by any chance did you mix your Crucial module with other RAM or are all RAM sticks the same?
From the tech guide, I don't know if you know: Memory modules should be installed in pairs of matched memory size, speed, and technology. If the memory modules are not installed in matched pairs, a slight reduction in performance may occur.
Name brands should also match. Dell's can be finicky about that and sometimes other PC's. One of our Rockstars, besides having a Dell laptop, has a homebuilt Asus. It can take 2 different brands of memory separately, but not mixed.
Did you try the Crucial module by itself?
Tom Hofmann
1 Rookie
•
10 Posts
0
November 2nd, 2019 21:00
Heil to Argentinia,
DDR3L ist Low-Volt . You need DDR3 .. not DDR3L
Tom Hofmann
1 Rookie
•
10 Posts
0
November 11th, 2019 18:00
speedstep
9 Legend
•
47K Posts
0
November 12th, 2019 14:00
Genuine
Should work fine
Specs: DDR3 PC3-12800 • CL=11 • Unbuffered • NON-ECC • DDR3-1600 • 1.35V • 512Meg x 64 • .