AMD with out-of-sync ram?

ThatFatCat5ThatFatCat5 Minn-eee-soda
edited January 2006 in Hardware
what would happen if someone attempted running a http://www.newegg.com/Product/Product.asp?Item=N82E16819103547 with DDR266 ram, would it run incredibly slow, not work at all?

and should it have DDR500 ram?

Comments

  • Sledgehammer70Sledgehammer70 California Icrontian
    edited January 2006
    Ddr500?
  • csimoncsimon Acadiana Icrontian
    edited January 2006
    on what mobo?
  • reelbigfishreelbigfish Boston, MA Member
    edited January 2006
    It only really needs PC3200 (DDR400). If you ran it with slower ram, it shouldn't matter as long as the motherboard supports the ram. If it is less than DDR400, it might be slower, but as I said will work depending on the motherboard.
  • RWBRWB Icrontian
    edited January 2006
    Technically it should work, but yeah it would be considerably slower due to memory bandwidth constraints. Stick with PC3200 or better if you can.

    It doesn't really matter what memory you use as long as it is DDR, it could be PC10,000 for all I care your motherboard will try to run it at whatever it supports, if it's PC1600 it will just run the ram as fast as it can which will probably be at PC1600 levels.
  • lemonlimelemonlime Canada Member
    edited January 2006
    RWB is correct, The Athlon64 platforms support slower DDR ram. I believe the A64 integrated memory controller 'officially' supports PC3200, PC2700 and PC2100. Not to say other slower models wont work with a little work. Faster memory (above PC3200) will simply run at PC3200 speeds unless you increase your base HTT (reference clock) thereby overclocking certain aspects of your system.
  • Omega65Omega65 Philadelphia, Pa
    edited January 2006
    The Latest core revisions of the Athlon 64 & X2 support an new Official PC4000 (DDR500 250mhz) speed, along with the regularPC3200 (DDR400 200mhz).

    If your mobo's BIOS is up to date and you drop a current revision CPU in, you'll see the option appear under the memory settings....

    That being said your PC will run fine with PC2100. The A64 Integrated Memory Controller will mask most of the performance loss of the slower ram
  • lemonlimelemonlime Canada Member
    edited January 2006
    Omega65 wrote:
    The Latest core revisions of the Athlon 64 & X2 support an new Official PC4000 (DDR500 250mhz) speed, along with the regularPC3200 (DDR400 200mhz).

    If your mobo's BIOS is up to date and you drop a current revision CPU in, you'll see the option appear under the memory settings....

    That is very interesting Omega, I have yet to hear anything about that. I know that they were contemplating a move to DDR500 instead of DDR2, however I didn't know there was any 'official' support for it today. Is this just a mainboard thing or is actually the IMC?

    Have any links to some more info? I'm just surprised that AMD would support something that requires the reference clock and HTT bus to be run outside of spec.
  • Omega65Omega65 Philadelphia, Pa
    edited January 2006
    It's not "Out of Spec" instead of HTT 5x 200mhz = 1000; it's HTT 4x 250mhz =1000 with the CPU multiplier reduced to the requiste number
    ex: Venice "E6" 3200+ 10X 200mhz = 2000mhz (HTT 5x 200mhz = 1000)
    or
    Venice "E6" 3200+ 8x 250mhz = 2000mhz (HTT 4X 250mhz = 1000)

    The news is several months old, and it didn't make much of a splash...

    Finally found some old info...
    Anandtech: Athlon 64 Revision E: Unofficial DDR500 Support New Memory Speeds

    OK the support may be Unofficial but it's there
  • lemonlimelemonlime Canada Member
    edited January 2006
    Omega65 wrote:
    The news is several months old, and it didn't make much of a splash...

    Finally found some old info...
    Anandtech: Athlon 64 Revision E: Unofficial DDR500 Support New Memory Speeds

    OK the support may be Unofficial but it's there

    Thanks for the link

    I'm surprised there wasn't more press on this :) I'm going to have to check this out. From the looks of that article, it's not even a multi drop and a reference clock increase, it appears to be async memory dividers that allow the memory to run faster than the reference clock, i.e. > 1:1. Very interesting.. :buck:
  • Omega65Omega65 Philadelphia, Pa
    edited January 2006
    The Athlon 64 has been Async from the beginning. After you set the HTT speed everything else is determined from that reference clock by multipliers and (for memory) dividers
  • lemonlimelemonlime Canada Member
    edited January 2006
    Omega65 wrote:
    The Athlon 64 has been Async from the beginning. After you set the HTT speed everything else is determined from that reference clock by multipliers and (for memory) dividers

    The multiplier part is correct, however the memory frequency is not determined from the reference clock (it sometimes works mathematically, but it sometimes does not). The memory frequency is based on an IMC selected 'divisor' of the CPU's operating frequency, not the reference clock.

    I.e. take an overclock of 8x300MHz (2400MHz) and a 5/6 divider.. should work out to 250MHz if it was indeed determined from the reference clock. If you try that combination, it actually comes out as 240MHz. Memory controller used [CPU Clock/10] not [300MHz*5/6]
  • Omega65Omega65 Philadelphia, Pa
    edited January 2006
    The Memory divider works from the closest (but higher) ratio available considering the CPU default Multiplier and the Memory Speed Selected

    ClockSpeed/Divider= Memory Speed

    Examples:

    FX-55 13x Multi HTT200 2600mhz
    DDR400 (200mhz) (Mem Ratio 1:1 (Ideal)) Memory Divider 13
    2600 / 13 = 200mhz

    DDR333 (166mhz) (Mem Ratio 6:5 (Ideal)) Memory Divider ((13)*6/5) = 15.6 = 16
    2600 / 16 = 162.50mhz

    DDR 266 (133mhz) (Mem Ratio 6:4 (Ideal)) Memory Divider ((13)*6/4) = 19.4 = 20
    2600 / 20 = 130.00mhz


    3200+ 10x Multi HTT200 2000mhz
    DDR400 (200mhz) (Mem Ratio 1:1 (Ideal)) Memory Divider 10
    2000 / 10 = 200mhz

    DDR333 (166mhz) (Mem Ratio 6:5 (Ideal)) Memory Divider ((10)*6/5) = 12
    2000 / 12 = 166.67mhz

    DDR266 (133mhz) (Mem Ratio 6:4 (Ideal)) Memory Divider ((10)*6/4) = 15
    2000 / 15 = 133.33


    3000+ 9X Multi HTT200 1800mhz
    DDR400 (200mhz) (Mem Ratio 1:1 (Ideal)) Memory Divider ((9)*1/1) = 9
    1800 / 9 = 200mhz

    DDR333 (166mhz) (Mem Ratio 6:5 (Ideal)) Memory Divider ((9)*6/5) = 10.8 = 11
    1800 / 11 = 163.63

    DDR266 (133mhz) (Mem Ratio 6:4 (Ideal)) Memory Divider ((9)*6/4) = 13.4 = 14
    1800 / 14 = 128.57

    Pics Below
    Opty 165 (9x) HTT278 with Memory set at 333mhz (6:5) ratio
    2502.7 / 11 = 227.51mhz Memory
    attachment.php?attachmentid=18984&d=1138562977attachment.php?attachmentid=18985&d=1138562977
  • lemonlimelemonlime Canada Member
    edited January 2006
    Omega65 wrote:
    The Memory divider works from the closest (but higher) ratio available considering the CPU default Multiplier and the Memory Speed Selected

    ClockSpeed/Divider= Memory Speed

    Yup, used to confuse the heck out of me till I finally wrapped my head around a64 dividers.. Same reason why half multipliers do funny things with the memory frequencies too. Oscar Wu made a good reference table with all of the actual DRAM frequencies a while back up to 5GHz..

    A64Divider.jpg
Sign In or Register to comment.