What bus speed are Durons and T-Birds

[RobUK]

As the subject states what bus speeds do the Durons and T-Brids have?

[drn]

they run at 100mhz default

[Jeff7]

Well, sort of 100MHz - I think the bus is DDR, so its effective transfer speed is equivalent to 200MHz.

[drn]

that is true but the board runs at 100 mhz and the cpu uses it as DDR to get it to 200 mhz

[AuraEdge]

Theres no unified FSB on the Athlon boards.
The CPU bus speed is 100Mhz, the Data bus speed is 100x2Mhz, and the memory speed runs at 100 or 133Mhz at default.

[Wilan Wong]

100MHz default, AMD calls it 200MHz Bus speed because it's DDR has the same transfer speed of a 200MHz Bus.

[RobUK]

So the Duron and t-bird use 100Mhz Bus and the DDR makes it 200MHz. Does the Athlon run on the same or is the bus really 200MHz??

[drn]

the Athlon runs the same as the Duron and the Tbirb

[RalphArch]

If you do have a duron and 133 memory - how do you make sure the memory is running at 133 instead of 100?

[RalphArch]

If you do have a duron and 133 memory - how do you make sure the memory is running at 133 instead of 100?

[OuTpaTienT]

uh, by going into the BIOS and setting the memory speed to 100 or 133.

[RalphArch]

uh - bios has no clear memory speed setting.
There is an auto detect DIMM/PCI Clock setting which can either be set to enabled or disabled. cpu/host setting can be varied from automatic to cpu-host spread spectrum in about 1 hz increments from 100 up to 112 - my system gets unstable about 106.

If I do set the autodetect - is there any way to tell what speed the memory is running at?

or could it be the bank dram timing setting? (has SDRAM 8/10ns plus DRAM fast and normal? Certainly no settings for 133.

[AuraEdge]

Youll only see settings for 133Mhz SDRAM speed if you have a KX133 or KT133 board.

[drn]

you must be runninig a Asus K7M for a mobo as they have fsb settings up to 150 mhz but they will only go to at the max 113 mhz if you got a real good one do to the AMD Irongate chipset

[RalphArch]

Thanks - on looking a little further it turns out I do have one setting that may apply - memory either host clock or host clock + 33. Since the host clock is 100 (or is it 200 as reported by SiSoft sandra due to the DDR) I guess this setting tries to drive memory at 133. The problem I have is when its set to that everything goes blank and I have to clear the cmos and reenter all the bios data to boot again (only works with this setting at host clock.

actually I have an M805LR (PCCHIPs). I don't know whether the motherboard doesn't support (clearly states in manual motherboard supports 100/133 memory bus, however - and also states the mb supports 200 or 266 FSB although AMD would/could not provide a cpu to verify) or if I got screwed when I purchased memory (the markings were for 133 - however Sisoft Sandra reports memory as 100[Smart modular 128 MB 16x(16Mx4) SDRAM PC100-222-622 (CL3 upto 100 MHz ) (Cl2 upto 100 MHz)] or if I just have the bios settings incorrect.

[Ultrakiller]

SO how do ya overclock a Tbird?
If you overclock the FSB, and its DDR, that mofo will burn

[papalion]

Ultrakiller - You overclock a T-bird by unlocking the clock multiplier. Do NOT screw around with the FSB speed, you will
fry that baby!

RalphArch- To my understanding (but i could be wrong),pc133 SDRAM is primarily for systems using Intel chips that utilize FSB speed of 133. Athlons are meant to run at 100MHZ (200 utilizing DDR), so pc100 SDRAM is just as good.

Second of all (and i'm not wrong), running memory at 133MHz usually gives you about a 3% perfomance gain over 100MHz - very neglegible and not noticable in day to day applications.

[drn]

if you dont have a unlock cpu and dont want to try to unlock it you can just up fsb a little at a time i run a slot a tbird 750 overclocked to 1100 mhz buy way of gfd set at 10x and fsb set to 110 mhz with would make it 220 mhz fsb so there is no way you will burn it up buy uping the fsb as long as you do it a little at a time

i have ran mine at 1100 mhz since the day i got it never even try to use it at defult speed of 750 set the gfd to 10 x and fsb to 110 mhz and votage at 1.75 and booted into window first time in fact i have had it up to 1200 mhz at 1.85 volts just to hot for me
i have had the fsb up to 115 mhz = 230 DDR

[papalion]

Yeah, but if you increase the FSB speed, your overdriving your PCI devices which can fry them. Unless of course, your BIOS gives you the option of setting your PCI bus speed seperately from the FSB by way of the fraction of the FSB.

For instance, normally the FSB is 100MHz, and PCI bus is 1/3 of FSB which = 33MHz. Now say, for instance, you increase the FSB to 133MHz without making any other changes. The PCI bus is now running at 1/3*133 which is 44.3MHz, not very safe for most PCI devices.

What i suggest, is explore your BIOS and see whether it has an adjustment for PCI bus and set it to 1/4 when your FSB is at 133MHZ.

The same issue applies to the AGP bus but the fraction is 2/3.

[This message has been edited by papalion (edited 09-21-2000).]

[neo_otyugh]

the bus speeds depend on the devices. some can handle higher speeds than others. i have run stuff as high as 50 on pci and 100 on agp and suffered in no way from it.

[otheos]

Ok, let's make this clear:

Athlon/T-Bird/Duron Run on 100Mhz Bus!

This is as follows:

CPU to Northbridge -> 100Mhz DDr = 200Mhz
Memory to Northbridge -> Asynchronous 100 /133Mhz or sunchronous 1:1 or 4:3 FSB
PCI -> 1/3 FSB = 33Mhz
AGP-> 2/3 FSB = 66MHz or Asynchronous always @ 66Mhz.

So if you change the FSB to 105Mhz:

CPU to Northbirdge goes to 210Mhz
Memory: Synchronous->105/140, Asynchronous->100/133
PCI goes to 35Mhz
AGP (synchronous) 70Mhz. or 66Mhz (Asynchronous)

Now 133MHz Mem gives just over 1GB/s bandwidth while 100Mhz gives only 800MB/s. That is not 3%, more like 20%. So there is a big difference.

If you overclock the FSB you will not necessarily fry your board.

If you set it for 105Mhz and leave both mem and AGP asynchronous to 100/133Mhz and 66Mhz respecively, you increased the performace of the EV6 bus, the CPU (raw Mhz) and the PCI bus. If your mem takes more than 133Mhz (say 166Mhz) then you can clock it synchronous to the FSB and get 140Mhz out of the 105FSB.

As long as your PCI (the only danger here) stays under 41Mhz (124MHz FSB -> not gonna happen with tese boards, sorry) you are ok.



[This message has been edited by otheos (edited 09-22-2000).]

[Peter M]

otheos, not quite. Here's what KT133 can do:

CPU bus: 100 or 133 MHz (no CPUs yet for 133 MHz). Effective throughput doubled by DDR technology, some ads have that as 200/266 MHz to spare the explanation.

AGP bus: At CPU/2 for 133 MHz CPUs, and 2/3 CPU for 100 MHz CPUs.

DRAM bus: At AGP bus speed, 33 MHz slower than CPU clock, same as CPU, or 33 MHz faster.

PCI bus: 33 MHz.

That's what the chipset supports. Next question is, what options do the usual clock synthesizers for KT133 offer.

With the way these work, with the overclocking choices just being increase-all-frequencies tweaks from a "legal" base setting, things go like this: If you choose to overclock from 100 or 133 MHz CPU bus, the other busses will increase their speed from their respective base frequency as well.

Like when you have 110 MHz CPU bus and your DRAM bus setting is 4/3, you'll get 147 MHz DRAM bus speed, 36 MHz PCI and 72 MHz AGP.

Regards, Peter


[This message has been edited by Peter Missel (edited 09-22-2000).]

[RalphArch]

Peter - or anyone out there that's had success with getting an M805LR motherboard to clock memory at 133 - can you tell me the bios settings that work please? I went to the show today and exchanged the memory i got one week ago (sold as 133 but reported 100 in SiSoft Sandra). So what's in machine now definitely reports PC133 (CAS3)[PC100 cas 2]. But if I set the memory speed in bios to host clock + 33 everything is black and the cmos must be jumpered and reset.

Is the setting for autodetect cpu and Dimm clocks supposed to be disabled to get 133 memory working - (possible other problems are cheap memory and maybe the motherboard really doesn't work with pc133??)