Transcend JM366D643A-50

Transcend will be best known to some of our readers as a manufacturer of flash memory. While flash memory is an important product line for Transcend, they also manufacture storage products and system memory. You will not find Transcend for sale at a huge number of US websites, but Transcend also sells directly to end-users at their website. Transcend has US sites in both Spanish and English, as well as several European language sites, and Taiwan, Japan and China websites.

The 1 Gigabyte of DDR400 arrived as two separate 512MB DIMMs. Transcend packaging is very similar to that used by Kingston for their value products.

There are no heatspreaders on the Transcend CAS 2.5 DIMMs. The memory chips are labeled JetRAM, which is a name used by Transcend for their memory chips. A quick check found 1GB of Transcend CAS 2.5 selling for around $100, which is a lower price than what we normally see for a CAS 2.5 memory.


Transcend rates JM366D643A-50 at DDR400 CAS 2.5 and we found the "auto" or SPD timings to be 2.5-3-3-8.

 Transcend JM366D643A-50 (DDR400) Memory Specifications
Number of DIMMs & Banks 2 DS
Total Memory
512 MB
Rated Timings 2.5-3-3
SPD (Auto) Timings 2.5-3-3-8
Rated Voltage 2.6V

Transcend shows both DDR400 CAS 2.5 and DDR400 CAS 3 in their product list, so it is clear that the DIMM products from Transcend are aimed at the Value end of the memory market.

Test Results

Transcend JM366D643A-50 - 2 x 512Mb Double-Bank
CPU Ratio at 2.4GHz Memory
Memory Timings
& Voltage
Sandra UNBuffered Sandra Standard
Super PI 2M places
(time in sec)
Wolfenstein - Radar - Enemy Territory fps
12x200 400 DDR 2.5-3-3-6
2.6V 1T
532.0 INT 2420
FLT 2593
INT 6050
FLT 6036
82 111.9
11x218 436 DDR 3-3-3-6
2.8V 1T
529.2 INT 2593
FLT 2735
INT 6393
FLT 6309
82 111.7
Highest CPU/Mem Performance 3-3-3-7
2.8V 1T
575.5 INT 2668
FLT 2835
INT 6650
FLT 5516
75 122.5
To be considered stable for test purposes, Quake3 benchmark, UT2003 Demo, Super PI, Aquamark 3, and Comanche 4 had to complete without incident. Any of these, and in particular Super PI, will crash a less-than stable memory configuration.

Transcend is another memory that costs just $100 for a Gigabyte and yet manages to nearly reach DDR450 in overclocking. The cost and performance are very similar to the Kingston CAS 3 rated Value RAM except that Transcend rates its Value RAM at CAS 2.5. While the rated timings differ, both Kingston and Transcend both are stable at CAS 2.5 at DDR400. The Transcend RAM is an excellent value and provides the overclocking capabilities to reach a 12% CPU overclock at 1:1 memory ratio.

We have looked at Aida 32 results in the past, and found them to be very useful in examining read/write performance and memory latency. Aida 32 is now available as Everest Home Edition, a free download from

Transcend JM366D643A-50 (DDR400) 2x512Mb Double-Bank
Everest 1.51
CPU Ratio at 2.4GHz Memory Speed Memory Timings
& Voltage
Everest READ
Everest WRITE
Everest Latency
12x200 400 DDR 2.5-3-3-6
2.6V 1T
5801 1861 47.7
11x218 436 DDR 3-3-3-6
2.8V 1T
6028 1906 48.8
Highest CPU/Mem Performance
446 DDR
2.8V 1T
6306 1989 47.9

It is easy to see in the Everest results that dropping CAS just from 2.5 to 3 in moving from DDR400 to DDR436 offsets virtually all of the performance improvements that you get from higher memory speed. The $100 Transcend reaches on to DDR446 to give you most of the headroom that you need for air-cooled 1:1 overclocking at stock multipliers.

OCZ PC3200 Gold: "Value BH5" Performance Comparisons


View All Comments

  • ChineseDemocracyGNR - Tuesday, April 12, 2005 - link

    "2) RAM multipliers are usually limited. If you have a standard set of 400, 320, and 266 speeds, you could only achieve DDR400 speed at a CPU frequency of 250. Anything lower than that would be running the RAM at less than 400. Most A64 CPUs can't do 250 on air at stock multipliers (the low end ones can) so they will be running less than optimum ram speed. That's where you could lower CPU multipliers or use a board like the DFI with lots of intermediate RAM ratios. "

    I'm not sure I'm following.

    With a 9x CPU multiplier, DDR266 memory divider and 312MHz reference clock the memory would be running at DDR400.
    With a DDR200 option you could go up to 400MHz on the reference clock. That means that no DDR400 memory will limit the overclock of a CPU with a 9x multiplier.

    "1) There is an Asynchronous Latency penalty, which can be tweaked somewhat on boards with better BIOS options like the DFI. It is not, hoever, the kind of asynchronous penalty you see on a FSB board like Intel. "

    In my own tests there's no real-world penalty at all. I compared an Athlon 64 running at:
    REFCLOCK: 200MHz
    Memory Divider: DDR400
    CPU multiplier: 9x
    LDT: 5x

    REFCLOCK: 300MHz
    Memory Divider: DDR266 (DDR400 effective)
    CPU multiplier: 6x
    LDT: 3x

    The results where near identical.

    "In other words, the easiest way to consistently improve memory performance is 1:1 memory speed."

    There's no memory fast enough to run at 1:1 with an Athlon 64. ;)
    An Athlon 64 at 9*200 is on a 1800/9 ratio with DDR400 memory.

    I'm sorry but I stand by what I said before, there's no reason to invest in memory if you want to overclock your Athlon 64, only if you want to overclock the memory as well.

    Kind of on the subject, I hope the round up of AMD PCI-E boards (there is one coming right?) tests the best reference clock the motherboards can achieve without memory as a limiting factor, unlike the reviews before.
  • PrinceGaz - Tuesday, April 12, 2005 - link

    Excellent review, both for the modules it covered and what it didn't.

    One small point- there is no such thing as 1:1 memory timings with A64 processors. The reduced latency and higher performance that a 1:1 ration gave when the processor to chipset FSB was running synchronously with the chipset memory-controller, is irrelevant with the Athlon 64 as there is no intermediate bus operating at a differnt speed to the memory controller to cause overheads. Selecting a lower memory speed just changes the CPU:Memory ratio in the processor.

    The memory on an Athlon 64 system works just as efficiently (though ay a lower bandwidth of course) if set to DDR333 as it does at DDR400, which means there is no real penalty when overclocking in choosing a lower memory speed to compensate for the increasing bus speed.
  • Olaf van der Spek - Tuesday, April 12, 2005 - link

    > Transcend is another memory that costs just $100 for a Gigabyte and yet manages to nearly reach DDR550 in overclocking.

    The table claims 510 (2 x 223), but 2 x 223 = 446.
  • Olaf van der Spek - Tuesday, April 12, 2005 - link

    Is Lavalys sponsoring this article? Why is that paragraph repeated on every page? Reply
  • JustAnAverageGuy - Tuesday, April 12, 2005 - link

    I would have liked to see Mushkin Blue

    ($147 per GB)

    and Corsair VS 2.5

    ($174 per gb)

    I won't whine about the voltage, that's been done before :)
  • Olaf van der Spek - Tuesday, April 12, 2005 - link

    - Reply
  • LX - Tuesday, April 12, 2005 - link

    Why isn't the OCZ4001024WV3DC-K on the OCZ site???
  • CobraT1 - Tuesday, April 12, 2005 - link

    If you are interested in the OCZ Value VX, note the differences in the two part numbers, one with a "W" and one without.
    Value VX = OCZ4001024WV3DC-K
    2.5-3-3-7 (picture) Supports EVP (Extended Voltage Protection)

    Value = OCZ4001024V3DC-K
    3-4-4-8 Does not Support EVP

    See this link for both.

    Hope this clears up the confusion.

  • segagenesis - Tuesday, April 12, 2005 - link

    Wesley - Fair enough. But when that ATACOM link posted in #44 shows 3-4-4 even on the label in the picture its hard to tell who to believe (and its hard to read the part # on it). If its all the same chip then fine... but why label it differently then? Buyer beware?

    Maybe I am off base...
  • Turin39789 - Tuesday, April 12, 2005 - link

    I get real tired pushing ferrari's out of my driveway. There isnt any racing alcohol available to me, sometimes I have my neghbor tow me to work in his chevrolet cobalt Reply

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