This post will be devoted to memory overclocking of DDR SDRAM. This memory type was the most popular between 2002 and 2005, replacing SDRAM and introducing double data rate to improve bandwidth. As per JEDEC standards, there are four official DDR speeds:
- 100 MHz (200 MHz data rate) – effective bandwidth 1600 MB/s
- 133 MHz (266 MHz data rate) – effective bandwidth 2133 MB/s
- 166 MHz (333 MHz data rate) – effective bandwidth 2666 MB/s
- 200 MHz (400 MHz data rate) – effective bandwidth 3200 MB/s
The effective bandwidth is calculated as speed * 8 (64 bits) * 2 (double data rate). This number can be also found on memory markings as PC rating, where it’s rounded to closest hundred (for 133 it’s PC-2100 and for 166 it’s PC-2700). Of course you can find other speed ratings which have been defined by manufacturers , maximum being 350 MHz (PC-5600) released by Patriot in limited numbers.
I will focus here on reaching maximum memory clock (suicide), no stability tests are going to be performed. As it turns out achieving 400 MHz memory clock (100% more than highest official speed) is possible, however several factors need to be considered:
- Motherboard
- CPU
- RAM
- BIOS settings
- Cooling
- OS and software.
At the moment of writing there were 18 official results of DDR memory clock result over 400 in the HWBOT database (however only one per person is displayed).
At the end of the post I am also sharing BIOS template that I use for memory binning, so I hope you can find it useful.
Motherboard
Proper motherboard choice is essential in every overclock. In this case I am going to use Socket 939 for Athlon 64 as Intel chipsets do not clock memory well enough. For that socket there is one ultimate motherboard to be used for overclocking – DFI LanParty NF4, preferred models are Ultra-D, SLI-D and SLI-DR. The Expert and Venus models could also be used, although they can exhibit compatibility issues with highly clocked RAM and might limit your OC.
Alternatively Socket 754 might be used, as it forces single channel memory, so the memory controller has less stress. Single channel is the way to go here.
CPU
Here the preferred CPU will be usual Athlon 64 with Venice core, so that 250 memory divider can be used. Opterons have worse IMCs (integrated memory controller) on the average, as well as San Diego cores. Newcastle and Winchesters don’t have 250 divider, so in that case CPU most be capable of high HTT in 1:1 with RAM.
Important – CPU must be tested for IMC capability as not all of them are capable of reaching 400 memory clock.
RAM
RAM must be selected carefully – it has to have Samsung TCCD or TCC5 memory chips, otherwise exceeding 300 MHz will be impossible without taking some extreme steps (voltage or cooling). You can identify the chips visually, if the RAM has no heatspreaders, or consult some of the RAM lists available online. Note that good PCB allows for better results, so look for non-reference PCB design (such as Brainpower).
My preferred models are A-Data Vitesta 566/600, G.Skill 4400/4800, Corsair 3200XL and Patriot 4800XBLK.
Note that you need high voltage supplied to the RAM to support the overclock. Safe values of voltage to be used 24/7 for TCCD/TCC5 chips are 2.7-2.9V, but in order to achieve highest clocks possible 3.3V will be used. Most of those chips stop scaling and start throwing a lot of errors after that mark, but there are some rare examples which can survive 3.5V and more.
BIOS settings
In terms of BIOS two things are important – BIOS version and settings. When it comes to version, you can use the latest or select one of those with memmory table for TCCD.
The memory will be configured using loosest timing possible.
Cooling
For cooling you have to remember two things:
- Keep the CPU warm.
- Keep the memory cool.
You might be tempted at first to cool the CPU as well, but AMD CPUs on Socket 939 exhibit cold bug which prevents them from operating above certain HTT. This HTT limit is related to CPU temperature and it goes lower with temperature drop, so in order to remove the limit it’s better to pump safe voltage (such 1.5-1.55V) and use air cooling.
For memory also some care is required, as Samsung TCCD have a cold bug, and most of them do not operate properly below 0 degrees Celsius. For most results it is sufficient to cool mems with a strong 120mm fan.
OS and software
Windows XP will be used, so if you have your favourite custom OS with most features removed, it will do great. You need two programs: CPU-Z for making setting validation and Clockgen for adjusting HTT settings (and you can always take a screenshot).
Let the fun part begin
The overclocking process will consist of two steps – first boot to OS, then slowly raise the clock and record the results.
End of part 1 🙂
BIOS template:
System 3000+ DFI NF4 SLI-D NF4LD329 bios Matrox G550 PCI-E 120GB WD 1200JB 650W Silverstone SLI PSU WinXP Pro SP3 NF4 6.66 chipset drivers 512MB Gskill PC4400LE @6x330mhz boot at 3.3v VID = 1.475 VID Special = Above Vid * 104% chipset = 1.4v LDT = 1.7v LDT x2.5 CPC = Disabled CAS Latency(CL) = 3 RAS to CAS(Trcd) = 7 Min RAS# Active time(Tras) = 15 Row Precharge Time(Trp) = 7 Row Cycle Time(Trc) = 22 Row Refresh Cycle Time(Trfc) = 24 Row to Row Delay(Trrd) = 7 Write Recovery Time(Twr) = 3 Write to Read Delay(Twtr) = 2 Read to Write Delay(Trwt) = 7 Refresh Period (Tref) = 3072 Odd Divisor Correct = Disabled DRAM Bank Interleave = Disabled Skew = Increase Skew Value = 255 DRAM Drive Strength = Level 5 or 7 DRAM Data Drive Strength = Level 3 DDRAM Response Time (510 series bios setting) = FAST or Normal / (618 bios) = Normal, Fast, Fastest Max Async Latency = 12ns Read Preamble Time = 8ns Idle Cycle Limit = 256 Dynamic Counter = Enabled R/W Queue Bypass = 16x Bypass Max = 7x 32 byte Granularity = Disable(8burst)
Phobos OC musings 