Athlon B vs C ??

[Guest]

I need to purchase a new PC with which I plan to work with digital audio and video, so I need a good deal of processing power on a budget. Having become aware that 1000 Mhz (and faster) Athlon Thunderbirds now come in type C (266 FSB) and type B (200 FSB) varieties, I have a couple FSB-related questions (I don't quite understand these terms). My questions: 1) Could you give me a rough idea of the average performance enhancement provided by the type C chip? [On one website, the 1000Mhz type C was over 25% more expensive than the type B variety.] 2) If I purchase a type B Athlon, would a KT133A-based motherboard provide significant performance benefits relative to the older KT133 chipset?

TIA and regards,

MJS

 

[Guest]

I made a similar choice myself a bit ago. Figure there are 3 clocks. The first is the base clock rate. Normally this is 100 mHz. It can be fiddled with, but changing it changes everything else in the system. (AGP and PCI bus rates, memory speed, and CPU speed.) The second is the memory clock rate. As I have seen it, it is either the base rate, or 4/3 of the base rate, either 100 or 133 mHz. AMD boards are getting extra data from there memory by a method I don't understand, but this accounts for the 200 and 266 Mhz busses which are advertised. I believe that also requires DDR memory, which is quite expensive. See www.pricewatch.com The final one is the CPU clock, which is multiplied off the base rate. From this, you can see that the CPU clocks may be the same and the only difference is the speed at which data is transfered.

According to AMD, there is only one speed of chip in common between the B and C models, namely the 1.2 gHz. See http://www.amd.com/products/cpg/athlon/ (Of course, this makes no account for overclocking.) Whatever website indicated a 1 gHz C model needs to be checked carefully before plunking your cash down.

I would expect that a 33% speed increase in data movement is noticable, perhaps far more noticable than a similar increase in CPU clock speed. The bottlenecks on most computer benchmarks are the speed of the graphics card, and by extension, the speed of the hard drive and memory.

The KT-133A based motherboards support 133 mHz SDRAM, while the KT-133 only go up to 100 mHz. Practically all SDRAM memory made at one rate will work at the other, which is a good reason for insisting on KT-133A.

The choice I made because of limited cash, was to forgo DDR memory. That made the B model CPU and 133 mHz memory a clear winner for my needs. As always, YMMV as well as the cash you have to spend.

Regards,
Thomas

There's no justice, there's just us.

 

[Guest]

"According to AMD, there is only one speed of chip in common between the B and C models, namely the 1.2 gHz."

The AMD site indicates that the 1gHz Athlon comes in both the 200mhz and 266mhz FSB varieties.

"I would expect that a 33% speed increase in data movement is noticable, perhaps far more noticable than a similar increase in CPU clock speed. "

So you think an 1.0 ghz type C would be faster than a 1.3gHz type B. If so, then the "C" chip may be worth the extra money. I'd still be interested in an estimate of the percentage of actual performance increase resulting from a 33% faster FSB.

You suggested that the advertised 200 and 266 Mhz FSB speeds require DDR memory to achieve. I do not think this is true. Can anyone verify?

"The KT-133A based motherboards support 133 mHz SDRAM, while the KT-133 only go up to 100 mHz."

Are you saying that 133mhz SDRAM would provide no performance improvement over the 100mhz variety for those with a KT-133 motherboard? I would be surprised if this is true.

Regards,

MJS

 

[Guest]

That's why it's called 200MHz/266MHz RAM, but in actuality DDR SDRAM... 100MHz or 133MHz DDR would confuse the public. Like you.

 

[Guest]

"The AMD site indicates that the 1gHz Athlon comes in both the 200mhz and 266mhz FSB varieties."

You are correct. I didn't notice the 1 gHz in common.

"I would expect that a 33% speed increase in data movement is noticable, perhaps far more noticable than a similar increase in CPU clock speed. "

"So you think an 1.0 ghz type C would be faster than a 1.3gHz type B. If so, then the "C" chip may be worth the extra money. I'd still be interested in an estimate of the percentage of actual performance increase resulting from a 33% faster FSB."

No, what I was saying is that 33% faster memory is more noticable than 33% faster processor. I have the B model chip and my memory is running at 133 mHz. That is part of what I don't understand, namely what the difference is between the memory speed and the FSB speed. however, I agree that a comparison of the chips would be nice to have, if there were a 1.3 gHz B model chip.

"The KT-133A based motherboards support 133 mHz SDRAM, while the KT-133 only go up to 100 mHz."

"Are you saying that 133mhz SDRAM would provide no performance improvement over the 100mhz variety for those with a KT-133 motherboard? I would be surprised if this is true."

No, I was clearly recommending purchase of a board with the KT-133A chipset because it allows the faster memory.

Regards,
Thomas

There's no justice, there's just us.

 

[Guest]

I copied the following from a review on this site or a similar site: "The ONLY major difference between this and
the previous KT133 is that the KT133A supports a 133 (266) MHz bus speed (used by the new 'C' type Athlons) for both the CPU and SDRam, whereas the KT133 only supported it for the SDRam." This leads me to believe that the old KT133 chipset supports 133Mhz SDRAM. I remain uncertain about whether KT133a boards provide any significant performance enhancement relative to KT133 boards when used with the type B Athlon.

 

[Guest]

I've got to remember to not write technical stuff when I'm pressed for time. From http://www6.tomshardware.com/mainboard/01q1/010122/index.html, "The only difference to its predecessor Apollo KT133 is the added support for the above mentioned 133 (266) MHz processor bus clock used by the new 'C'-type Athlons." As I look over my notes, I realized that I chose the KT133A motherboard for it's upgradeability, not for any specific advantage over KT133 motherboards. Having chosen to buy 850 B-type Tbirds for my current machines, I figure that I'll be able to upgrade cheaply to C-type Tbirds in a year or so. However, to make that doable, I had to get 133 mHz memory now. Judging from most of what I read on this board, price was far more of a concern for me than most people.

Regards,
Thomas

There's no justice, there's just us.

 

[TDH]

Has anyone successfully ran a "B" class T-bird (with the L1 bridges closed) at 133Mhz CPU bus? I'm running a A7V133 with a "B" class 1.1 T-bird. If I reduce the clock multiplier to lets say 8X133 (to get close to 11X100) the system won't even post. Or do I need to get a "C" class chip to be able to get to 133 CPU bus?

Thanks.

The only reason that I am saying this is that I swore I saw a article here (by Tom) showing where he had a "B" class running @133 CPU bus. *Shrugs*

 

[Guest]

nope, people were posting at 133 before the c even came out. You can even post at 150+. The cpu's don't seem to have a problem reaching that fsb but you mem and other peripherals do.

 

[slvr_phoenix]

Which is really the point of going with a motherboard that supports the 133MHz FSB instead of just overclocking a whole system. Because then even if you overclock a 100MHZ FSB chip to a 133MHz FSB, the rest of the system is still in-spec. (At least it is if you put 133MHz or higher RAM in it.)

- Sanity is purely based on point-of-view.

 

[Guest]

Not to pick on you in particular, many ppl post questions to which THG has pretty much already answered. Unless you want a personal experience, most questions will go unanswered if the answer is easily found either on THG or this forum. The sig of the week definitely has merit. And just to help a bit, <A HREF="http://www4.tomshardware.com/mainboard/01q1/010104/index.html" target="_new">http://www4.tomshardware.com/mainboard/01q1/010104/index.html</A> has the skinny on most if not all of your C/B 100Mhz/133Mhz questions.


The glass isn't half empty, it isn't half full. There just isn't enough in it.

 

[Guest]

So DDR SDRAM is required to achieve the 200/266MHz FSB? If so, this memory speed/bus speed issue would make more sense to me. My confusion was caused by having seen Athlon systems advertised as having 200MHz FSB with PC100 or PC133 SDRAM system memory.

 

[Guest]

I did in fact read the article you referenced, as well as others pertaining to the Athlon CPU and KT133a chipset. Lacking a background in computer technology, however, I've had difficulty understanding some of the info and making logical inferences about issues not explicitly addressed in the articles. For example, the article stated that the type B Athlons "communicated with the system at a clock of 100 MHz, which offers a data bandwidth of 64-bit/8-byte x 100 MHz x 2 = 1600 MB/s, due to the fact that Athlon's processor bus is 'double-pumped', which is why this bus is commonly referred to as a 200 MHz bus." This statment, combined with ads for Athlon systems with 200MHz FSB and SDR memory, led me to (incorrectly?) believe that this FSB speed could be obtained with PC100 SDR memory.

Can you recommend a computer hardware forum which may be more accommodating to newbies?

Regards,

MJS

 

[khha4113]

<b>So DDR SDRAM is required to achieve the 200/266MHz FSB?</b>
NO. Only in AMD 760 chipset and the upcoming VIA KT-266 chipset. KT-133(A) chipsets support only SDRAM (PC100 and 133)

 

[Guest]

I was aware that the KT-133(a) chipsets do not support DDR memory. I was/am confused about whether the 200/266MHz FSB is attained using SDR memory (PC100 and 133). Are you saying that it is? This seems to conflict with my limited knowledge by suggesting that the CPU can receive info faster than the SDR memory can provide.

Regards,

MJS

 

[Guest]

The "C" Athlon in combination with the KT-133A chipsets run at 266 FSB with PC133. I don't believe that the 266Mhz FSB is supported with PC100 but I'm not totaly sure on that one. But the price difference between PC100 and PC133 is nil anyway.

I didn't mean to pick on you, but most ppl seem to ask questions that have already been answered in these forums or in THG reviews. THG is one of the better review sites around. Until you get up to speed, this forum should help.


The glass isn't half empty, it isn't half full. There just isn't enough in it.<P ID="edit"><FONT SIZE=-1><EM>Edited by dv8shawn on 03/01/01 02:53 AM.</EM></FONT></P>

 

[mousepotato]

AMD is misleading people a little by calling the FSB frequencies for their CPU's: 200/266. This is a marketing thing to promote the DDR memory. The DDR (Double Data Rate) memory allows for twice the data per cycle to be transferred. So AMD claims double FSB speeds. The acual frequencies are still 100/133.

 

[gregorarch]

I think you'll find that the FSB is double-pumped anyway (and always has been even since the Athlon Classic), so technically it is 200/266. How much use this is with single-pumped SDRAM is probably debatable. DDR lets you double-pump the memory as well.

 

[Guest]

When people refer to 200 mhz fsb or 266 mhz fsb, they are
referring to the internal speed at which the athlon\duron
processes information at. The pc100 or pc133 specs refer
to the speed at which the memory processes data. The two
stats for the most part are independent of each other.
When you set the fsb for your m-board, the athlon\duron
processes the data at twice said value internally, hence
a 100 front side bus becomes a 200 internal bus speed, but
only inside the athlon\duron itself. Similarly, a 133 fsb
becomes an internal bus speed of 266 mhz.
Thats the speed the chip talks to itself... As for the
PC100/PC133 specs, that refers to the speed which the
memory runs at. Currently, if you have PC100 memory, you
can only run it on a athlon\duron that runs on a 100(200)
mhz fsb. But if you have PC133 memory, you can run it at
either 100(200) or 133(266) mhz fsb.
The information some people has given has been slightly
incorrect. Not completely, by slightly.
As for using a b type athlon\duron at the 133(266) mhz bus
speed, you can do it, you just need to connect the L1
bridges on the chip. I just received my Iwill KK266 mboard
yesterday, and replaced my Soyo K7VTA.
I only really have one day of experience with the new board
with the newer chipset, but so far 3dmark 2000 has shown a
decent cpu speed increase at the same processor speed.
BTW, I'm running a Duron 800 at 1000.
The KT133A in my opinion, is a good choice for a chipset,
currently. There are alot of choices right now, which is
what I believe has lead to all the confusion in the posts.

All in all, here's the main things...
You can run a b athlon\duron at the higher fsb, you just
need to properly unlock the L1 bridges.

If you decide to run at the higher fsb, you will need PC133
compliant memory.

My advice, pick the KT133A chipset, and a B type Athlon, at
whatever speed fits your budget, and good quality PC133
memory. I use crucial, but there are other good brands.
Then unlock the athlon, and set the fsb to 133 when you
setup the computer. Make sure that you set the multiplier
lower. (1000 mhz=10*100 where as 1000 mhz=7.5*133)

Good luck,
BC (sorry so long, but it all needed to be posted at once)