FX vs Opty: Why Isn't the HT Ever Mentioned?

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View

Hi All:

I tried searching through the FAQs and webs for this question, but could not
find the answer anywhere.  In the specs for some of the A64s and the FXs at
newegg the HT is listed as 2 GHz, but for the Optys it is listed as 1 GHz.
Pretty much the reviews on the web say that the FXs are basically the same
as the Optys except the Optys have better Silicon because they are designed
for servers and the FXs have a multiplier that is upwards unlocked.  With
the fast FSBs that the A64s have, the upwards multipler of the FXs is not
very important?

So, do the 2 GHz A64s and FXs  have an HTT (is it the sames as HT) that run
at 2 GHz and a 250 MHz FSB would use a muliplier of 8?  If so is there any
benefit from this faster HT and that is why it is never mentioned?  Or do
the HTs all run at the same frequency 1 GHz and in some cases it is doubled
because the data lines are double and there is no difference among the A64,
FX, and Opty  chips?



Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Quoted text here. Click to load it

I didn't find the AMD web site too good at clearing this up.

As far as I know, all the processors use the same 16 bit wide busses.
There is a 16 bit "up" bus, and a 16 bit "down" bus. (Each bus
bit is transmitted differentially, with two wires, a logic 0 on
one wire and a logic 1 on the other wire. The wires are doing
the opposite of one another.).

The data pattern on a bus bit, is clocked at either 800MHz or 1000MHz.
This depends on which processor in the family we are talking about.
The data is transmitted DDR (double data rate), so a bit is sent on
the rising and on the falling edge of the clock.

To work out the bandwidth, it is:

   16 bits * 1000MHz * 2 (for ddr)
   ------------------------------- = 4GB/sec on a 16 bit HT bus.
    8 bits per byte                  (4GB/sec "up", 4GB/sec "down")

If you had a socket 754 processor, that drops to 3.2GB/sec, due to
the 800MHz HT bus speed spec.

Newegg only repeats what it finds at AMD for tech info. AMD is
not very precise on their web site, and the marketing folks
play fast and loose.

I expect all the S939 processors are the same, since they all share
the same spec (31411.pdf). It is just careless marketing folks
multiplying by 2 whenever they feel like it :-)

Socket 754
   "The HyperTransport link of the processor is capable of operating
    at 200, 400, 600, and 800 MHz (400, 800, 1200, and 1600 MT/s

Socket 939
   "The HyperTransport link of the processor is capable of operating
    at 200, 400, 600, 800, and 1000 MHz (400, 800, 1200, 1600, and 2000 MT/s

Socket 940
   "The HyperTransport link of the processor is capable of operating
    at 400, 800, 1200, and 1600 MT/s."

I think the tech writer was getting tired when the S940 spec was

Further background:
(from http://www.hypertransport.org/tech/tech_whitepapers.cfm )

And "better Silicon" ? Is this like regular and extra-crunchy ?

It all comes off the same wafers, and is speed sorted on a
tester. In the same way that enthusiasts buy and sort the good
processors from the bad ones, sending the bad ones to Ebay :-)
An Opteron may have a larger margin between its operating speed
and the max (overclockable) speed, but this is just a function of
the sorting process. And if you've been keeping track, you'll
notice that the more recent Opterons don't have the same monster
overclocks of some of the earlier ones - it makes you wonder why.
A cynical market manipulation perhaps ? If you are shopping for
overclockable processors, it pays to keep track of the trends.


Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Quoted text here. Click to load it
Quoted text here. Click to load it
Quoted text here. Click to load it
Quoted text here. Click to load it

Thanks for clearing this all up for me.  I have one of the newer Opteron
150s, I can't seem to get it stable in windows XP64 at anything about 2.8
GHz, so AMD must be getting better at the sorting process.  I can run prime
stabile at 2.85 GHz, but get periodic BSODs every several days, although
memtest will run for 24 h at 2.95 GHz without error.

Best wishes,


Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Quoted text here. Click to load it

Is there any chance that is a WinXP64 driver issue ? You'd think if
it was Prime stable, it would behave itself. If you are a gamer,
you can still have problems when gaming, so Prime is not the
final authority in that sense, but if you are building a number
cruncher, Prime should be a pretty good indicator. (I'd find the
level at which it is Prime stable, and then turn it down a bit, to
provide some margin.)

Are you using the stock Vcore or have you increased it a bit ?
I'm just curious as to how hard you had to push it, to get it
to overclock.

One thing you could try, is get a copy of Knoppix (knopper.net),
which is a "read-only Linux". You don't need to install the OS,
as when Knoppix boots from a CD, it puts essential operating files
in a RAM disk. I've run four copies of Prime95 on top of Knoppix,
as a stability check. The only benefit of using Knoppix in your
case, would be to see whether the OS does the equivalent of BSOD
while the machine is running. (The reason for running four copies,
is you could assign a chunk of memory to each copy, and in my case
Prime always errored out in the same memory area. Based on that,
I changed out my RAM. But since you don't have any Prime errors,
there is no need to zoom in on where the errors happen.)

If you can, collect all the details you can get from each
BSOD, and see if there is a pattern to where the BSODs happen.
If you get lucky, the pattern may hint at what is broken.


Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Quoted text here. Click to load it

Hi Paul:

I have not tried switching to Linux yet.  It might not be worth the hassle.
One problem is that most of my input data is in the form of Excel
spreadsheets.  MATLAB's embedded Excel functions do not work, so you need to
have Excel installed from MS office so Matlab can read the spreadsheets
correctly.  I would have to hope that the Star Office Excel clone would work

I am running Vcore at 1.55 V, but I also have pretty good cooling with a
Thermaltake CL-P0024 Copper Cooling Heatsink with 2 Tt A2017 90mm Fans.
However, I feel that I should have pulled the IHS off the chip first and
probably it was a waste of AS5 to use it on the top of the secondary

Running Prime I hit mid 50 Cs, max 55 C and MATLAB, I am average 45 C with
maxing at 50 C.  I noticed that I dropped the chipset voltage to 1.6 V, so I
put it back up to 1.8 V.  I also noticed that when I had to install Windoze
64 a second time, because I had corrupted it the first time, that I forgot
to install the graphics driver.  Thinking of the driver issue, I installed
the evga eVGA 128-TC-2N27-SX Geforce 6200 LE TC driver (I guess it is
obvious now that I am not a gamer).

I will try Knoppix out, it sounds like a great way to preview unix and to
bench mark MATLAB with plunging in head first.  I hate the thought of
another windows install.  I am really interested to see if Unix will get me
about 2.85 GHz.  The last BSOD was memory management failure.

Right now once I cross 2.9 GHz it is instant BSOD using clock gen.

Best wishes and thanks for the help,


Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

On Sat, 27 May 2006 19:18:44 +0000, Pete wrote:

Quoted text here. Click to load it

They are all the same. 1GHz. Newegg has it wrong.

Quoted text here. Click to load it

No, there aren't any that run at 2GHz. And AFAIK there aren't any with a
default 250MHz FSB either. The current HT multiplier is from 2x-5x. The
default speed of the HT link is 1000MHz on socket 939 cpu's (5x200).

Quoted text here. Click to load it

Woth memory having it's own seperate bus, the external HT Link speed ahs
almost no bearing on performance. 600, 800, 1000, you won't notice the

Quoted text here. Click to load it
Well, you can set the freq different for up and down, but 1000MHz is the
default for socket 939 and 800MHz for socket 754. You can find out all you
want to know about HT here.


Want the ultimate in free OTA SD/HDTV Recorder? http://mythtv.org
http://mysettopbox.tv/knoppmyth.html Usenet alt.video.ptv.mythtv
My server http://wesnewell.no-ip.com/cpu.php
HD Tivo S3 compared http://wesnewell.no-ip.com/mythtivo.htm

Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Quoted text here. Click to load it

Thanks for the info, Wes.  I feel much better now about  my Opty purchase.

Best wishes,


Re: FX vs Opty: Why Isn't the HT Ever Mentioned?

Also keep in mind the older Opteron 940's (Sledgehammer) ran 800mhz and the
newer Opteron 940's (Troy) run 1000mhz speeds, respectively. I'm not talking
about the super new AM2's.

Tyan Thunder K8WE
Dual Opteron 252s (2.6ghz)
4 gig Corsair XMS DDR400 RAM
XFX 7800 GTX 256 w/VGAsilencerV3
500 gig Hitachi SATA 300
160 gig Seagate SATA 150
Dual Dell 24" wide aspect LCDs
550W Antec power supply
X-Fi Platinum Soundblaster
Quoted text here. Click to load it

Site Timeline