does anyone know if the new Xserve's CPUs can actually use the memory bandwidth of the DDR ram? there was a lot of talk about how the DDR memory was being wasted on the earlier Xserves and G4s. Has anything changed? Are the G4 chips different now?
<strong>does anyone know if the new Xserve's CPUs can actually use the memory bandwidth of the DDR ram? there was a lot of talk about how the DDR memory was being wasted on the earlier Xserves and G4s. Has anything changed? Are the G4 chips different now?</strong><hr></blockquote>
The bus on the new CPUs runs at 167Mhz... the DDR memory is still being 'wasted'.
Notice, I put 'wasted' in quotes so I wouldn't get posts like yours. Anyone who has been following the discussions about Apple's DDR implementation would already know the details. In CPU-bound tasks, the extra bandwith may indeed be wasted.
[ 02-11-2003: Message edited by: Mac The Fork ]</p>
<strong>Notice, I put 'wasted' in quotes so I wouldn't get posts like yours. Anyone who has been following the discussions about Apple's DDR implementation would already know the details. In CPU-bound tasks, the extra bandwith may indeed be wasted.
[ 02-11-2003: Message edited by: Mac The Fork ]</strong><hr></blockquote>
Well then you basically started a pissing contest. Whether the DDR is "Wasted" or not will depend on what each individual expects from the use of DDR. JLL wasn't attacking your post but rather clarifying this I believe.
What tends to happen is people start the bad habit of calling the Xserve "Fake DDR" and other misleading statements. We deserve more complete information here.
<strong>Notice, I put 'wasted' in quotes so I wouldn't get posts like yours. Anyone who has been following the discussions about Apple's DDR implementation would already know the details. In CPU-bound tasks, the extra bandwith may indeed be wasted.
[ 02-11-2003: Message edited by: Mac The Fork ]</strong><hr></blockquote>
Boy those single quotes REALLY cleared up the point you were tryng to make.
So much for simple answers. The PowerPC G4 is incapable of fully using the fast DDR RAM used in the Xserve and Power Mac. The system controller, however, is able to provide DMA (direct memory access) at full speed. This means that programs can tell the system controller to shuttle data between, say, the IDE controller and memory without routing the data through the processor. There are two advantages to this in the case of the Xserve and Power Mac:
1) The processor is free to continue with other tasks while these transfers are occurring.
2) Where everything other than the processor has a fast connection to memory, transfers are faster than they would be if data was routed to the processor along the G4's slow bus.
However, in tasks that are CPU-bound (where computation rather than IO is critical), the relatively slow bus of the G4 becomes a bottleneck. I would say that the bandwidth of the DDR memory is wasted in these tasks, since processors like the Athlon and Pentium 4, for instance, do not exhibit that bottleneck and can communicate at full speed with memory. For file servers, the bottleneck doesn't matter, since the processor isn't doing much. For other tasks, it can come into play.
Some potential misconceptions:
- Xserve doesn't use the DDR memory.
It does, at full speed, for everything but the processor.
- Xserve is slow.
It is potentially slower than it would be if the processor itself supported DDR. However, that has nothing to do with tasks where the bus between the processor and the system controller is not used.
I-bent-my-wookie, I really could have done without your needlessly rude post. I'm pretty sure it's against the posting guidelines anyway.
[ 02-11-2003: Message edited by: Mac The Fork ]</p>
The bus on the new CPUs runs at 167Mhz... the DDR memory is still being 'wasted'.</strong><hr></blockquote>
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
so... any news/rumors on when Apple is going to switch out the CPU to a model that can handle DDR bandwidth? perhaps a 333 or 400 front side bus?
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
so... any news/rumors on when Apple is going to switch out the CPU to a model that can handle DDR bandwidth? perhaps a 333 or 400 front side bus?</strong><hr></blockquote>
Future Hardware my friend!
A whole smear of threads devoted to just that topic
[quote] so... any news/rumors on when Apple is going to switch out the CPU to a model that can handle DDR bandwidth? perhaps a 333 or 400 front side bus? <hr></blockquote>
The PPC 970 FSB will be half the processor speed
1.8Ghz= 900Mhz bus. Is that fast enough for you?
[quote]
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
<hr></blockquote>
Yes..sometimes however the BEST Software reverb you can buy bar none is Audioease's Altiverb and it's not available on PC's <img src="graemlins/cancer.gif" border="0" alt="[cancer]" />
Geeks all think they are superior and reconstruct poor communication so that they can claim they intended to mean something when, in fact, they were trying to be anal exit ports (or, in some cases, anal entry ports - ymmv).
This is a sign of a lack of respect to the group as a whole and should be smacked-down by the group humans who actually deal with other people on a daily basis.
Comments
<strong>does anyone know if the new Xserve's CPUs can actually use the memory bandwidth of the DDR ram? there was a lot of talk about how the DDR memory was being wasted on the earlier Xserves and G4s. Has anything changed? Are the G4 chips different now?</strong><hr></blockquote>
The bus on the new CPUs runs at 167Mhz... the DDR memory is still being 'wasted'.
<strong>
The bus on the new CPUs runs at 167Mhz... the DDR memory is still being 'wasted'.</strong><hr></blockquote>
Sigh
The bandwidth is NOT wasted. Harddrives, Ethernet, FireWire and more have Direct Memory Access, and they use the remaining bandwidth.
That's why a Single 1GHz Xserve beats the crap out of a Dual 1GHz QuickSilver when running I/O demanding applications.
[ 02-11-2003: Message edited by: Mac The Fork ]</p>
<strong>Notice, I put 'wasted' in quotes so I wouldn't get posts like yours. Anyone who has been following the discussions about Apple's DDR implementation would already know the details. In CPU-bound tasks, the extra bandwith may indeed be wasted.
[ 02-11-2003: Message edited by: Mac The Fork ]</strong><hr></blockquote>
Well then you basically started a pissing contest. Whether the DDR is "Wasted" or not will depend on what each individual expects from the use of DDR. JLL wasn't attacking your post but rather clarifying this I believe.
What tends to happen is people start the bad habit of calling the Xserve "Fake DDR" and other misleading statements. We deserve more complete information here.
<strong>Notice, I put 'wasted' in quotes so I wouldn't get posts like yours. Anyone who has been following the discussions about Apple's DDR implementation would already know the details. In CPU-bound tasks, the extra bandwith may indeed be wasted.
[ 02-11-2003: Message edited by: Mac The Fork ]</strong><hr></blockquote>
Boy those single quotes REALLY cleared up the point you were tryng to make.
Communications major in college?
1) The processor is free to continue with other tasks while these transfers are occurring.
2) Where everything other than the processor has a fast connection to memory, transfers are faster than they would be if data was routed to the processor along the G4's slow bus.
However, in tasks that are CPU-bound (where computation rather than IO is critical), the relatively slow bus of the G4 becomes a bottleneck. I would say that the bandwidth of the DDR memory is wasted in these tasks, since processors like the Athlon and Pentium 4, for instance, do not exhibit that bottleneck and can communicate at full speed with memory. For file servers, the bottleneck doesn't matter, since the processor isn't doing much. For other tasks, it can come into play.
Some potential misconceptions:
- Xserve doesn't use the DDR memory.
It does, at full speed, for everything but the processor.
- Xserve is slow.
It is potentially slower than it would be if the processor itself supported DDR. However, that has nothing to do with tasks where the bus between the processor and the system controller is not used.
I-bent-my-wookie, I really could have done without your needlessly rude post. I'm pretty sure it's against the posting guidelines anyway.
[ 02-11-2003: Message edited by: Mac The Fork ]</p>
<strong>
The bus on the new CPUs runs at 167Mhz... the DDR memory is still being 'wasted'.</strong><hr></blockquote>
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
so... any news/rumors on when Apple is going to switch out the CPU to a model that can handle DDR bandwidth? perhaps a 333 or 400 front side bus?
<strong>
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
so... any news/rumors on when Apple is going to switch out the CPU to a model that can handle DDR bandwidth? perhaps a 333 or 400 front side bus?</strong><hr></blockquote>
Future Hardware my friend!
A whole smear of threads devoted to just that topic
The PPC 970 FSB will be half the processor speed
1.8Ghz= 900Mhz bus. Is that fast enough for you?
[quote]
thanks for confirming what i thought. i am looking to use one for digital audio/real-time dsp/plug-ins etc. all of these are *very* CPU intensive tasks and hence are crippled by the 'wasted' bandwidth.
<hr></blockquote>
Yes..sometimes however the BEST Software reverb you can buy bar none is Audioease's Altiverb and it's not available on PC's <img src="graemlins/cancer.gif" border="0" alt="[cancer]" />
Geeks all think they are superior and reconstruct poor communication so that they can claim they intended to mean something when, in fact, they were trying to be anal exit ports (or, in some cases, anal entry ports - ymmv).
This is a sign of a lack of respect to the group as a whole and should be smacked-down by the group humans who actually deal with other people on a daily basis.
In other words, Don't be a MtForkin' ass, please.
Really, I meant, please be nice. Honest.