Out of the Loop

[Trashdog]

Ok, it’s been about 3 years since I put a system together. I remember
the Athlon, Athlon XP, Duron, and Thunderbird, but what on earth is a
Sempron chip? Where does it fall in line at? I assume the Athlon XP’s
are still top of the lne for AMD but where does the Sempron fall?

 

[George Macdonald]

Ok, it’s been about 3 years since I put a system together. I remember
the Athlon, Athlon XP, Duron, and Thunderbird, but what on earth is a
Sempron chip? Where does it fall in line at? I assume the Athlon XP’s
are still top of the lne for AMD but where does the Sempron fall?

No Athlon XP is long surpassed as AMD's top of the line - for 2 years now
we've had the Athlon64... available currently in socket 754 and 939 configs
with single and dual channel memory controllers respectively. More
recently there are dual core versions. Sorting out which one to buy can be
confusing: e.g. the Athlon64 3500+ has been available over the past year
based on no less than 5 different cores. Take a look here for a summary:
http://www.c627627.com/AMD/Athlon64/

The Sempron fills a similar market slot to Duron and Intel's Celeron, i.e.
the "value" end though it is also confusing in that Sempron has been
applied to both low-end Athlon XPs for socket A and, more recently, low-end
Athlon64s for socket 754. It's been said here that if you take the Sempron
model number and knock off 400MHz, that'll be its approximate equivalent
Athlon64 performance. It's basically a chip for the OEM market to offer
product differentiation; I see no reason for a DIYer to consider it unless
they're really hard up.

 

[Grumble]

No Athlon XP is long surpassed as AMD's top of the line - for 2 years now
we've had the Athlon64... available currently in socket 754 and 939 configs
with single and dual channel memory controllers respectively. More
recently there are dual core versions. Sorting out which one to buy can be
confusing: e.g. the Athlon64 3500+ has been available over the past year
based on no less than 5 different cores. Take a look here for a summary:
http://www.c627627.com/AMD/Athlon64/

The Sempron fills a similar market slot to Duron and Intel's Celeron, i.e.
the "value" end though it is also confusing in that Sempron has been
applied to both low-end Athlon XPs for socket A and, more recently, low-end
Athlon64s for socket 754. It's been said here that if you take the Sempron
model number and knock off 400MHz, that'll be its approximate equivalent
Athlon64 performance. It's basically a chip for the OEM market to offer
product differentiation; I see no reason for a DIYer to consider it unless
they're really hard up.

I respectfully disagree ;-)

The S754 Palermo Sempron64 2800+ is functionally equivalent to a S939
Venice Athlon64 3000+: they both support AMD64, SSE2, SSE3, and have the
same memory controller. (Does that mean they support the same memory
dividers? I'm not sure about that.)

The differences are:
256KB L2 cache vs 512KB
single channel vs dual channel
1.6 GHz vs 1.8 GHz
AFAIU, Sempron64 2800 does not support CnQ (but 3100 does).

For half the price (78 vs 149) you get 80% of the performance.

However, it's true that socket 754 is on its way out... But the same
could be said for socket 939, no? AMD wants to move to socket M2 with a
DDR2 memory controller.

How much life is there left in S754? and in S939?

It also sucks to miss out on Cool'n'Quiet. So much so that I can't
decide between a Sempron64 3100+ (if I could find one for ~90 EUR) and
an Athlon64 3000+ (the performance difference should be less than 10%).

 

[Tony Hill]

Ok, it’s been about 3 years since I put a system together. I remember
the Athlon, Athlon XP, Duron, and Thunderbird, but what on earth is a
Sempron chip? Where does it fall in line at? I assume the Athlon XP’s
are still top of the lne for AMD but where does the Sempron fall?

The Duron marketing name is no more and the Sempron name replaced it.
The chips themselves are different (some are actually identical to
AthlonXP chips), but it's filling the same price-point.

As for the AthlonXP, it's pretty outdated now and all but
discontinued. The Athlon64 and it's derivatives are top-dog now. The
Athlon64 comes in 3 varieties now, the plain-standard Athlon64 which
offers 64-bit capabilities, integrated memory controller and a number
of performance enhancements over the AthlonXP. These are available in
the older single memory channel "Socket 754" version and the newer
(not really worthwhile anymore IMO), dual channel memory "Socket 939"
version.

The next variety is the Athlon64 FX, which is basically just a bigger
and badder Athlon64 (either higher clock speed or more cache than the
standard model). Unfortunately it does so with a rather large price
tag, only for those with deep pockets. Still, it is the fastest
single-core x86 processor out there.

The last and, IMO, most interesting version is the Athlon64 X2
dual-core processors. These chips have two Athlon64 processing cores
in a single package. Their core speed isn't quite as high as the
Athlon64 FX chips, but having two processors in one more than makes up
for it in my opinion.

As for the Sempron's, right now they come in two varieties. One, as I
mentioned above, is physically identical to old AthlonXP chips, just
with a different numbering scheme (ie a Sempron 3000+ is basically the
same as an AthlonXP 2600+). The other a small-cache version of the
Socket 754 Athlon64, often with the 64-bit capabilities disabled.

 

[Yousuf Khan]

Ok, it’s been about 3 years since I put a system together. I remember
the Athlon, Athlon XP, Duron, and Thunderbird, but what on earth is a
Sempron chip? Where does it fall in line at? I assume the Athlon XP’s
are still top of the lne for AMD but where does the Sempron fall?

Duron has now become Sempron.

Athlon XP has now become Athlon 64.

Those of course are their market positionings.

Yousuf Khan

 

[chrisv]

The Athlon64 and it's derivatives are top-dog now. The
Athlon64 comes in 3 varieties now, the plain-standard Athlon64 which
offers 64-bit capabilities, integrated memory controller and a number
of performance enhancements over the AthlonXP. These are available in
the older single memory channel "Socket 754" version and the newer
(not really worthwhile anymore IMO), dual channel memory "Socket 939"
version.

What? Socket 939 "not worthwhile anymore"? What's better?

 

[koko]

Duron has now become Sempron.
Athlon XP has now become Athlon 64.

Those of course are their market positionings.

and in the real world
Athlon XP was renamed to Sempron
later on Athlon 64 was modified(cache) to became Sempron

 

[George Macdonald]

I respectfully disagree ;-)

The S754 Palermo Sempron64 2800+ is functionally equivalent to a S939
Venice Athlon64 3000+: they both support AMD64, SSE2, SSE3, and have the
same memory controller. (Does that mean they support the same memory
dividers? I'm not sure about that.)

The differences are:
256KB L2 cache vs 512KB
single channel vs dual channel
1.6 GHz vs 1.8 GHz
AFAIU, Sempron64 2800 does not support CnQ (but 3100 does).

I've no idea why they'd disable CnQ, which I consider an important benefit,
but you forgot about the 800MHz vs. 1000MHz HT. It'd also be worth finding
out if the Sempron supports 1T command rate on memory accesses.

For half the price (78 vs 149) you get 80% of the performance.

To save ~$70. on a complete system, that's "hard-up" to me.

However, it's true that socket 754 is on its way out... But the same
could be said for socket 939, no? AMD wants to move to socket M2 with a
DDR2 memory controller.

How much life is there left in S754? and in S939?

From my POV, s754 was out of the picture about a year ago - I moved on.

It also sucks to miss out on Cool'n'Quiet. So much so that I can't
decide between a Sempron64 3100+ (if I could find one for ~90 EUR) and
an Athlon64 3000+ (the performance difference should be less than 10%).

I think you'll find that performance is worse than 10% loss when pushed,
i.e. when you really need it... and CnQ is a big part of the "platform"
advantage. If you're also buying a mbrd, it makes no sense to me to not go
s939 even for Sempron.

 

[Tony Hill]

What? Socket 939 "not worthwhile anymore"? What's better?

LOL! I gotta work on connecting my brain to my fingers a bit better
before posting! I was referring to the Socket 754 Athlon64 chips as
not being particularly worthwhile anymore.

Socket 939 chips are, of course, the latest and greatest for AMD.

 

[Felger Carbon]

LOL! I gotta work on connecting my brain to my fingers a bit better
before posting! I was referring to the Socket 754 Athlon64 chips as
not being particularly worthwhile anymore.

Tony, if your application(s) are limited by CPU performance, then
you're right. If the CPU is not the limiting factor, then Sempron
754s are an excellent value. Esp the 3400+, which has C&Q, A64, SSE3
and all the other latest goodies AMD chips have, at a very good price.

 

[Grumble]

I've no idea why they'd disable CnQ, which I consider an important benefit,

I've spent a whole day researching CnQ. I'm not sure what AMD means when
they say "this CPU supports CnQ, but this CPU does not support CnQ." As
far as I understand, consumer-grade K8 CPUs (not Opteron or FX) support
all the multipliers between 4x (?) and the rated multiplier. Thus, a
3000+ A64 supports 4x through 9x, not 10x and above.

Does "support for CnQ" mean one can change the multiplier and voltage
DYNAMICALLY, i.e. within the protected-mode OS? On the flip side, "no
support for CnQ" would mean that one cannot change the multiplier and
voltage dynamically... Does that mean AMD would intentionally disable
that feature in S754 Sempron64s below 3000+?

On a related note, I found this article rather interesting:
http://www.silentpcreview.com/article231-page1.html

It was written before Sempron64s came out, and seems to imply
CrystalCPUID can be used to change voltage and multiplier on-the-fly,
even in S754 Semprons (as long as the motherboard supports it.)

but you forgot about the 800MHz vs. 1000MHz HT.

As far as I understand, on a uniprocessor system, the frequency of the
hypertransport link is unimportant. The HT link only handles PCI-E,
SATA, GigE, USB2, FireWire, etc traffic from the chipset to the CPU.

Neoseeker set the LDT to 200 MHz and played with several HT multipliers.
In most benchmarks, there was no noticeable difference between 200 MHz
and 1000 MHz HT!

http://www.neoseeker.com/Articles/Hardware/Guides/athlon64oc/2.html

What's the max thoughput of PCI-E 16x ? Do modern graphics card saturate
the entire PCI-E link?

It'd also be worth finding
out if the Sempron supports 1T command rate on memory accesses.

Palermo cores are supposed to have the same memory controllers Venice
cores have.

To save ~$70. on a complete system, that's "hard-up" to me.

What you don't know is that I'm a cheap bastard ;-)

From my POV, s754 was out of the picture about a year ago - I moved on.

Hmmm, With socket M2 6-9 (??) months away, how much life is there left
in S939?

I think you'll find that performance is worse than 10% loss when pushed,
i.e. when you really need it... and CnQ is a big part of the "platform"
advantage. If you're also buying a mbrd, it makes no sense to me to not go
s939 even for Sempron.

I need to understand exactly what AMD means by CnQ. If every S754
Sempron supports dynamic multiplier and voltage scaling, then I'll just
use CrystalCPUID in Windows, and the native cpufreq support in Linux.

I'm guessing AMD intentionally disables dynamic scaling to make
high-price parts more attractive...

The cpuinfo in Linux has several flags of interest:
static char *x86_power_flags[] =
{
"ts", /* temperature sensor */
"fid", /* frequency id control */
"vid", /* voltage id control */
"ttp", /* thermal trip */
};

P.S. I found this on Asus's website:

Question

Why can't I find FID/VID adjust option in the BIOS of K8N series
motherboard? My CPU model is AMD Sempron Processor.

Answer

Due to the CPU's limitation, FID/VID adjust option will be hidden in
BIOS if system detect user installs those Sempron Processor which can
not support Cool 'n' Quiet function.ex: Sempron 2600+ or Sempron 2800+.

So it does look like my guess is right...

I'm still collecting info.
e.g. http://www.ocworkbench.com/ocwb/ultimatebb.php?/topic/30/4794.html

Anyway, thanks for the input, George.

 

[Grumble]

Tony, if your application(s) are limited by CPU performance, then
you're right. If the CPU is not the limiting factor, then Sempron
754s are an excellent value. Esp the 3400+, which has C&Q, A64, SSE3
and all the other latest goodies AMD chips have, at a very good price.

For ~ the price of a Palermo Sempron64 3400+ (S754, 2.0 GHz, 256 KB L2),
you can get a Venice Athlon64 3000+ (S939, 1.8 GHz, 512 KB L2). On the
one hand you get an extra 200 MHz, on the other hand you get 256 KB more
L2 cache and dual channel. Tough call in terms of performance.

But in terms of the upgrade path, I'd go S939. No contest.

 

[Tony Hill]

Note that I was specifically speaking about Socket 754 Athlon64 chips,
not the Socket 754 Sempron chips. Sempron's can be fine if you're
apps aren't very CPU intensive and you're on a tight budget, though
I'm not sure that the 3400+ is a very good example.

For ~ the price of a Palermo Sempron64 3400+ (S754, 2.0 GHz, 256 KB L2),
you can get a Venice Athlon64 3000+ (S939, 1.8 GHz, 512 KB L2). On the
one hand you get an extra 200 MHz, on the other hand you get 256 KB more
L2 cache and dual channel. Tough call in terms of performance.

But in terms of the upgrade path, I'd go S939. No contest.

Agreed. Even in terms of performance I would tend to give the nod to
the Athlon64 3000+ for probably 90% of all apps out there. FWIW
Newegg shows the price of the two chips at $135 for the Sempron64
3400+ vs. $146 for the Athlon64 3000+, not exactly a large difference.
You might save another ~$10 on the motherboard side as well, but even
for a barebones system a difference of $20-$25 isn't much.

 

[Felger Carbon]

For ~ the price of a Palermo Sempron64 3400+ (S754, 2.0 GHz, 256 KB L2),
you can get a Venice Athlon64 3000+ (S939, 1.8 GHz, 512 KB L2). On the
one hand you get an extra 200 MHz, on the other hand you get 256 KB more
L2 cache and dual channel. Tough call in terms of performance.

Not a tough call at all if you already have a 754 mobo or two that
you're happy with. ;-)

But in terms of the upgrade path, I'd go S939. No contest.

Upgrade a 754 mobo or two with an S939 CPU?? ;-)

 

[George Macdonald]

I've spent a whole day researching CnQ. I'm not sure what AMD means when
they say "this CPU supports CnQ, but this CPU does not support CnQ." As
far as I understand, consumer-grade K8 CPUs (not Opteron or FX) support
all the multipliers between 4x (?) and the rated multiplier. Thus, a
3000+ A64 supports 4x through 9x, not 10x and above.

The problem is that the docs are hopelessly out of date: in several other
docs, AMD refers to the Power and Thermal data Sheet (30430.pdf) but it
hasn't been updated for a year and the latest CPU shown there is the
Winchester 3500+. According to it though, some processors have 3
intermediate power states, others 2 and yet others, none. I can't find
anything specific on Sempron64 CnQ support, other than a year old Sempron
3100+ in the above doc, which has no intermediate P-states; whether that
means it can oscillate between max & min P-states for CnQ, as opposed to
ramping up and down through intermediates, I dunno.

Does "support for CnQ" mean one can change the multiplier and voltage
DYNAMICALLY, i.e. within the protected-mode OS? On the flip side, "no
support for CnQ" would mean that one cannot change the multiplier and
voltage dynamically... Does that mean AMD would intentionally disable
that feature in S754 Sempron64s below 3000+?

Yes, with the driver from AMD loaded, the BIOS support and the right
setting in the OS -- Minimal Power Management in WinXP -- the voltage and
clock are varied dynamically. Have you seen where AMD states that Semprons
have "no CnQ support"?

On a related note, I found this article rather interesting:
http://www.silentpcreview.com/article231-page1.html

It was written before Sempron64s came out, and seems to imply
CrystalCPUID can be used to change voltage and multiplier on-the-fly,
even in S754 Semprons (as long as the motherboard supports it.)


As far as I understand, on a uniprocessor system, the frequency of the
hypertransport link is unimportant. The HT link only handles PCI-E,
SATA, GigE, USB2, FireWire, etc traffic from the chipset to the CPU.

HT handles *all* DMA traffic to/from I/O devices. As usual, more is
generally considered better.

Neoseeker set the LDT to 200 MHz and played with several HT multipliers.
In most benchmarks, there was no noticeable difference between 200 MHz
and 1000 MHz HT!

http://www.neoseeker.com/Articles/Hardware/Guides/athlon64oc/2.html

I have to ask: where did this guy get the term "LDT bus"?... I suspect a
label in a BIOS Setup screen? He seems to use it for the what is simply
the system base clock and in fact Lightning Data Transport was the original

What's the max thoughput of PCI-E 16x ? Do modern graphics card saturate
the entire PCI-E link?

PCI-e has a max bandwidth of 4.1GB/s and HT has a max of 4GB/s in each
direction so the possibility is there for overload if you count in other
traffic, though I doubt that it currently needs that much in most (anny
cuurent) video cards. Integrated chipset graphics could possibly could
change the picture there I guess.

Palermo cores are supposed to have the same memory controllers Venice
cores have.


What you don't know is that I'm a cheap bastard ;-)


Hmmm, With socket M2 6-9 (??) months away, how much life is there left
in S939?

As much as s754 had a year ago? What it achieves now is what interests
me - 6GB/s memory bandwidth out of a $200. CPU and a $100. mbrd is actually
kinda mind-boggling when you look back just a short time. It's going to be
interesting to see how M2 plays out - memory latency is going to take a
hit.

I need to understand exactly what AMD means by CnQ. If every S754
Sempron supports dynamic multiplier and voltage scaling, then I'll just
use CrystalCPUID in Windows, and the native cpufreq support in Linux.

Understanding CnQ "exactly" is going to be difficult - the algorthms are
described in the BIOS & Kernel Developer's Guide (26094.PDF). How it
behaves and how to achieve that are a bit easier: with BIOS support and the
AMD driver. AMD doesn't show a Linux driver for the Sempron but the
Sempron driver package for WinXP is the same as the one for Athlon64, so
possibly the Athlon64 Linux driver would work for Sempron?