Yeh your right, i thought that was Merom (Core 2 Duo - for laptops), but i checked closer - theyve put the desktop (Conroe) under laptop chips?, i should have suspected that Merom tops out @ 2.33G.... I was referring to my trusty little PB Al 1.25G. \
Yeah the naming is a bit ass-ed. Core 2 Duo mobile is Merom which tops out at 2.33ghz. Core 2 Duo for desktop is Conroe, which hits a few higher notes on the ghz scale
The 6700 and 6800 with a solid heatsink and fan can probably be overclocked up to and maybe past 3ghz. The ExtremeE6800 has an unlocked multiplier so you could go X12, X13 - that is, overclocking without having to raise the FSB. With the other models, you have to raise the FSB clock to overclock the CPU, and then adjust the multipliers on the RAM speed and RAM latency settings for stability. The E6700 I'd say can hit 2.8ghz on air easy with a nice heatsink in a PC setup with one of these babies:
edit: Overclocking Conroe in PC setups, I am not sure on how the ram dividers work, not sure if it is kinda same as in socket 939, AM2 for AMD or Netburst Pentiums. My initial research shows that if you go for decent 800mhz DDR2 ram and adjust the latency timings your CPU overclocking via bus speed increase can be quite successful. Or go up to 1066 DDR2 ram... Anyway, DDR2 667 is workable as well... So, whatever, I'm not going to go to a Conroe system from my AMD for quite some while, so I'll figure the ram stuff out at some later time when it is more relevant and useful. If Apple comes out with a Conroe Mac Pro we'll have to see what speed RAM they decide to use. 800mhz DDR2 I think.
Okay. figured out the RAM speed and stuff as related to Intel stuff and Apple. I'm gonna brain dump onto this post, for those interested in how Apple runs it's machines stock and for those interested in building a Conroe PC to choose RAM. Apologies if this is all old news.
The fact is that the memory runs asynchronously with the front side bus in most cases, depending on the FSB:Memory divider. Synchronous is when FSB:Memory is 1:1. Which means that Yonahs could use 533mhz RAM. But remember higher speed RAM results in higher RAM latencies so lower speed RAM with lower latencies sort of cancel each other out. This has been proven in many PC benchmarks. The best is to have high speed RAM with real low latencies (expensive "overclockerz extreme!!!one11!!" type RAM)
There's some decimal places which we'll generally ignore in all our calculations. Intel, Apple, other manufacturers have decided to what extent they'll use the decimal places of FrontSideBus, Memory and CPU speeds.
Okay. Let's Roll.
Yonah.
FrontSideBus is 166mhz. x11, x12, x13 on the cpu multiplier gives you 1.83ghz, 1.99ghz, 2.16ghz - speeds of MacBook, MacBookPro, and iMac Core Duo. How convenient
FrontSideBus is Quad-pumped = 166*4 = almost 664
DDR2 memory in all the above models is 667mhz (effective).
Which means FSB : Memory ratio is 1:2, that is 166 : 332
As it is DDR2 the 332mhz is running at 664mhz.
Note: 166mhz is the approx. FSB speed used by Intel/Apple to calculate the CPU speeds at x11, x12, x13 cpu multipliers.
Conroe.
FrontSideBus is 266mhz. x8, x9, x10, x11 on the cpu multiplier
gives you 2.13ghz, 2.39ghz, 2.66ghz, 2.93ghz
speeds of next iMac? low-end Woodcrest? I leave it to you
FrontSideBus is Quad-pumped = 266*4 = 1064mhz (1066mhz Intel designated)
What DDR2 memory will Conroe use?
FSB:Memory ratio 1:1 = 266:266 = 532(DDR2 remember), you can use 533mhz (effective) DDR2 RAM
FSB:Memory ratio 1:2 = 266:532 = 1064(DDR2 remember), you can use 1066mhz (effective) DDR2 RAM
Now you ask, how will Apple use 800mhz DDR2 (effective) memory, since 1066mhz DDR2 is maybe quite expensive?
Depends on what FSB:Memory ratio they put in the EFI Bios
Given 266mhz FSB, We want the closest memory divider between 266 and 400 (DDR2 remember is 800mhz effective)
Closest is 400/266 = 1.5 = FSB:Memory ratio of 2:3
FSB 266 * 1.5 = 399, so this will allow use of 800mhz DDR2 effective in Conroes from Apple.
Overclocking:
In overclocking in PCs, All conroes except the top model have locked multipliers. So you adjust bus speed up from 266mhz. Push it to 300mhz and your 2.66ghz conroe goes to 3ghz (3ghz at last, as promised by Stevie J )
What memory speed will you need? Depends on the FSB:Memory multipliers
Okay, that's all for now. Phew. Please feel free to correct any errors.
I don't understand your 1:2 and 2:3 ratios. The 5000X chipset is a quad channel memory bus, so with 667MHz memory, the memory bus should have the same bandwidth as the two CPU busses combined. Before someone objects, each processor package has its own independent bus to the chipset.
I don't understand your 1:2 and 2:3 ratios. The 5000X chipset is a quad channel memory bus, so with 667MHz memory, the memory bus should have the same bandwidth as the two CPU busses combined. Before someone objects, each processor package has its own independent bus to the chipset.
(Long post, but the magic comes at the end )
The memory ratio comes into play when you are using higher speed RAM than is "necessary". For example, look at the Yonah setup in Yonah Macs. Running a 1:1 ratio is 166:166 ; 166*2 = 332mhz DDR2 effective that is only really needed. But Apple uses 667mhz DDR2 effective memory. So the mobo chooses a ratio (depending on mobos) that will bring the *actual* speed of the RAM closest to the rated DDR2 effective speed. In this case, 1:2 ratio is 167:332 ; 332*2 = 664mhz.
In DDR2 setups, as mentioned before, there is a trend towards higher speeds from 533mhz, 667mhz, 800mhz, 1066mhz - higher speeds require the FSB to memory divider ratio to be adjusted. Higher speeds = higher latency which as mentioned cancel out each other unless you have high speed RAM AS WELL AS lower latency ("overclocker RAM").
Let's look at Conroe. Bus speed 266mhz. Bring that up to 360mhz. If you run a divider at 1:1 then 360:360 ; 720mhz DDR2 effective is the speed that the RAM is running. So either you'd need a 667mhz DDR2 that can run at that higher speed or simply pop in a 800mhz DDR2 that will run at the slower speed.
The idea of ratios is simply to try and get the best fit between actual RAM speed (based on bus speed) and the RATED speed of the DDR2 RAM.
You are right about the Woodcrest only needing 667mhz RAM, and indeed it looks like FB-Dimms only running at 533mhz or 667mhz that are available now.
Indeed, look at Conroe at stock speeds: bus is 266mhz, 1:1 divider gives you 266:266 ; 532mhz DDR2 effective is the speed that the RAM is running, so 533mhz DDR2 RAM is enough.
With Conroes, we will see people putting in higher speed RAM than 533mhz, such as 667mhz, 800mhz, and even 1066mhz. Which again, may not be necessary since the lower speed RAM has lower latency which equates to similar performance more or less with higher speed RAM at higher latency.
My 1:2 and 2:3 ratios for Xeon Woodcrest was simply conjecture at this stage. Let's say you could pop in a 1066mhz FB-Dimm.
Woodcrest bus is 333mhz. If you could only run 1:1 divider, then that's
333:333 ; your RAM is only running at 666mhz effective. So here you have a 1066mhz FB-Dimm running only at 666mhz. Not making the most of your RAM sticks...!
Actually here my calculations need to be refined. I've been assuming FB-Dimms are similar to DDR2 in some way, multiplying by 2.
But I think FB-Dimms, if you say it's 533mhz or 667mhz, it is that. It's not double-data-rate like DDR, or DDR2, or DDR3s (DDR is twice the rate, DDR2 is also twice the rate, DDR3 is also twice the rate, the 2 and 3 at the end of DDR speaks of the generation of DDR, DDR3 doesn't mean 3 times the data rate).
Okay, so back to FB-Dimms. If you look at it and say it is running at 667mhz. Pop it into a Xeon Woodcrest. Bus speed is 333mhz. So actually, the bus speed to memory ratio is 1:2 , so that 333mhz : 666mhz. If the bus speed to memory ratio was 1:1 , then 333mhz : 333mhz which means your FB-Dimm was only running at 333mhz, quite a "waste" since it is rated at 667mhz.
Now, if you pop in a 533mhz FB-Dimm, you'd have to have a memory divider close to 2:3. Because 2:3 = 333: (333*1.5) = 333:500 = FB-Dimm 533mhz rate running at 500mhz.
So I have probably made a mistake in my earlier post about FB-Dimms because I was assuming they are double-data-rate which they may not be (?). Assuming they are not double-data-rate then the calculations show that to make the most of the *rated* speed of the FB-Dimm, the mobo has to adjust the memory ratio to run the FB-Dimm at the closest speed to its *rated* speed.
I guess what I'm discussing here is Yonah and Conroe mainly. What we need to keep in mind is the *convention* that the front side bus speed is the starting point.
Conroe:
266mhz bus speed
multiplier for "effective FSB" = x4 = 1066 MT/s or just 1066 mhz
multiplier for CPU speed = eg. x10 = 2.66 ghz
multiplier for RAM speed = eg. x1.5 = 399 mhz, so 798 mhz DDR2 effective, can use 800mhz DDR2 sticks.
I was just exploring the core bus speed (before the quad pump) to memory speed ratio, which is really just talking about the multiplier for RAM speed above. On Intel systems now, apparently it can be x1.0, x1.5, etc. but *unlike AMD mobos* it cannot be less than x1.0 whereas AMD can have x0.66 x0.5 or something like that.
This is where I am going to pull out when it comes to discussing how the bus, CPU and memory channels all communicate with each other, that's way beyond my knowledge now.
So especially looking at Woodcrest Xeons and what FB-Dimms are supposed to do, I know that we are looking at the Glidewell platform which features the Intel 5000X (Greencreek) chipset, which has now support for PCI Express x16 bus required for graphics cards.
What the "bus speed multiplier for RAM speed" and FB-Dimms and overall how the bus works with CPU and RAM channels and all that, I am lost. I've edited my post on Xeon Woodcrest fsb:memory ratios to reflect that it is really, just guessing at this stage.
Comments
Originally posted by jdcfsu
I doubt Apple will go that route. The Merom will take over the notebook line as it should
Yeah, I totally agree. I was just saying, Conroe could wind up in some notebooks (really almost desktop replacements)
Yeh your right, i thought that was Merom (Core 2 Duo - for laptops), but i checked closer - theyve put the desktop (Conroe) under laptop chips?, i should have suspected that Merom tops out @ 2.33G.... I was referring to my trusty little PB Al 1.25G.
Yeah the naming is a bit ass-ed. Core 2 Duo mobile is Merom which tops out at 2.33ghz. Core 2 Duo for desktop is Conroe, which hits a few higher notes on the ghz scale
http://www.tomshardware.com/2006/07/...out_athlon_64/
Core 2 Model ...Clock Speed ...\tMultiplier ...\tFront Side Bus Speed ...\tL2 Cache
Extreme X6800 ...\t2,933 MHz ...\tx11 ...\t266 MHz (FSB1066 QDR) ...\t4 MB
Duo E6700 ...\t2,666 MHz ...\tX10 ...\t266 MHz (FSB1066 QDR) ...\t4 MB
Duo E6600 ...\t2,400 MHz ...\tX9 ...\t266 MHz (FSB1066 QDR) ...\t4 MB
Duo E6400 ...\t2,133 MHz ...\tX8 ...\t266 MHz (FSB1066 QDR) ...\t2 MB
Duo E6300 ...\t1,866 MHz ...\tX7 ...\t266 MHz (FSB1066 QDR) ...\t2 MB
The 6700 and 6800 with a solid heatsink and fan can probably be overclocked up to and maybe past 3ghz. The ExtremeE6800 has an unlocked multiplier so you could go X12, X13 - that is, overclocking without having to raise the FSB. With the other models, you have to raise the FSB clock to overclock the CPU, and then adjust the multipliers on the RAM speed and RAM latency settings for stability. The E6700 I'd say can hit 2.8ghz on air easy with a nice heatsink in a PC setup with one of these babies:
edit: Overclocking Conroe in PC setups, I am not sure on how the ram dividers work, not sure if it is kinda same as in socket 939, AM2 for AMD or Netburst Pentiums. My initial research shows that if you go for decent 800mhz DDR2 ram and adjust the latency timings your CPU overclocking via bus speed increase can be quite successful. Or go up to 1066 DDR2 ram... Anyway, DDR2 667 is workable as well... So, whatever, I'm not going to go to a Conroe system from my AMD for quite some while, so I'll figure the ram stuff out at some later time when it is more relevant and useful. If Apple comes out with a Conroe Mac Pro we'll have to see what speed RAM they decide to use. 800mhz DDR2 I think.
The fact is that the memory runs asynchronously with the front side bus in most cases, depending on the FSB:Memory divider. Synchronous is when FSB:Memory is 1:1. Which means that Yonahs could use 533mhz RAM. But remember higher speed RAM results in higher RAM latencies so lower speed RAM with lower latencies sort of cancel each other out. This has been proven in many PC benchmarks. The best is to have high speed RAM with real low latencies (expensive "overclockerz extreme!!!one11!!" type RAM)
There's some decimal places which we'll generally ignore in all our calculations. Intel, Apple, other manufacturers have decided to what extent they'll use the decimal places of FrontSideBus, Memory and CPU speeds.
Okay. Let's Roll.
Yonah.
FrontSideBus is 166mhz. x11, x12, x13 on the cpu multiplier gives you 1.83ghz, 1.99ghz, 2.16ghz - speeds of MacBook, MacBookPro, and iMac Core Duo. How convenient
FrontSideBus is Quad-pumped = 166*4 = almost 664
DDR2 memory in all the above models is 667mhz (effective).
Which means FSB : Memory ratio is 1:2, that is 166 : 332
As it is DDR2 the 332mhz is running at 664mhz.
Note: 166mhz is the approx. FSB speed used by Intel/Apple to calculate the CPU speeds at x11, x12, x13 cpu multipliers.
Conroe.
FrontSideBus is 266mhz. x8, x9, x10, x11 on the cpu multiplier
gives you 2.13ghz, 2.39ghz, 2.66ghz, 2.93ghz
speeds of next iMac? low-end Woodcrest? I leave it to you
FrontSideBus is Quad-pumped = 266*4 = 1064mhz (1066mhz Intel designated)
What DDR2 memory will Conroe use?
FSB:Memory ratio 1:1 = 266:266 = 532(DDR2 remember), you can use 533mhz (effective) DDR2 RAM
FSB:Memory ratio 1:2 = 266:532 = 1064(DDR2 remember), you can use 1066mhz (effective) DDR2 RAM
Now you ask, how will Apple use 800mhz DDR2 (effective) memory, since 1066mhz DDR2 is maybe quite expensive?
Depends on what FSB:Memory ratio they put in the EFI Bios
Given 266mhz FSB, We want the closest memory divider between 266 and 400 (DDR2 remember is 800mhz effective)
Closest is 400/266 = 1.5 = FSB:Memory ratio of 2:3
FSB 266 * 1.5 = 399, so this will allow use of 800mhz DDR2 effective in Conroes from Apple.
Overclocking:
In overclocking in PCs, All conroes except the top model have locked multipliers. So you adjust bus speed up from 266mhz. Push it to 300mhz and your 2.66ghz conroe goes to 3ghz (3ghz at last, as promised by Stevie J
What memory speed will you need? Depends on the FSB:Memory multipliers
Which you have in your (old-skool) PC Bios.
Use 1:2 --- 300*2 = 600 = 1200mhz DDR2 effective. Ouch.
Use 1:1 --- 300*1 = 600mhz DDR effective.
Up the bus speed to 350mhz, CPU 2.66ghz goes to 3.5ghz (may be possible stable)
Use 1:1 --- 350*1 = 700mhz effective. Which means you can use overclocked 667mhz sticks or run with 800mhz sticks underclocked.
So overclocking in PC land by upping the bus speed will have you needing to adjust memory dividers and overclocking or underclocking your RAM.
Woodcrest Xeon
I will stop now and not discuss Xeon, except for the following factors:
Assuming Quad-pumped bus, that's 333mhz for 1333mhz FSB.
On the highest model, that's a x4 CPU clock multiplier.
Conjecture on FSB:memory dividers:
(edit: removed now, as some may have mentioned only 533mhz and
667mhz FB-Dimms are available at this stage)
Okay, that's all for now. Phew. Please feel free to correct any errors.
http://www.intel.com/technology/memo...dr2_fbdimm.htm
I predict Apple will go for 667mhz FB-Dimms. (edit: memory ratio removed). Just a prediction, they could use 533mhz, but that sounds a bit slow now
Originally posted by sunilraman
Woodcrest Xeon
I will stop now and not discuss Xeon, except for the following factors:
Assuming Quad-pumped bus, that's 333mhz for 1333mhz FSB.
On the highest model, that's a x4 CPU clock multiplier.
Conjecture on FSB:memory dividers:
1:1 = 666mhz effective (you could use 667mhz DDR2??)
1:2 = 1332mhz effective (is there FBDIMM 1333mhz ram??)
2:3 = 999mhz effective (probably FBDIMM 1066mhz ram??)
Okay, that's all for now. Phew. Please feel free to correct any errors.
I don't understand your 1:2 and 2:3 ratios. The 5000X chipset is a quad channel memory bus, so with 667MHz memory, the memory bus should have the same bandwidth as the two CPU busses combined. Before someone objects, each processor package has its own independent bus to the chipset.
I don't understand your 1:2 and 2:3 ratios. The 5000X chipset is a quad channel memory bus, so with 667MHz memory, the memory bus should have the same bandwidth as the two CPU busses combined. Before someone objects, each processor package has its own independent bus to the chipset.
(Long post, but the magic comes at the end
The memory ratio comes into play when you are using higher speed RAM than is "necessary". For example, look at the Yonah setup in Yonah Macs. Running a 1:1 ratio is 166:166 ; 166*2 = 332mhz DDR2 effective that is only really needed. But Apple uses 667mhz DDR2 effective memory. So the mobo chooses a ratio (depending on mobos) that will bring the *actual* speed of the RAM closest to the rated DDR2 effective speed. In this case, 1:2 ratio is 167:332 ; 332*2 = 664mhz.
In DDR2 setups, as mentioned before, there is a trend towards higher speeds from 533mhz, 667mhz, 800mhz, 1066mhz - higher speeds require the FSB to memory divider ratio to be adjusted. Higher speeds = higher latency which as mentioned cancel out each other unless you have high speed RAM AS WELL AS lower latency ("overclocker RAM").
Let's look at Conroe. Bus speed 266mhz. Bring that up to 360mhz. If you run a divider at 1:1 then 360:360 ; 720mhz DDR2 effective is the speed that the RAM is running. So either you'd need a 667mhz DDR2 that can run at that higher speed or simply pop in a 800mhz DDR2 that will run at the slower speed.
The idea of ratios is simply to try and get the best fit between actual RAM speed (based on bus speed) and the RATED speed of the DDR2 RAM.
You are right about the Woodcrest only needing 667mhz RAM, and indeed it looks like FB-Dimms only running at 533mhz or 667mhz that are available now.
Indeed, look at Conroe at stock speeds: bus is 266mhz, 1:1 divider gives you 266:266 ; 532mhz DDR2 effective is the speed that the RAM is running, so 533mhz DDR2 RAM is enough.
With Conroes, we will see people putting in higher speed RAM than 533mhz, such as 667mhz, 800mhz, and even 1066mhz. Which again, may not be necessary since the lower speed RAM has lower latency which equates to similar performance more or less with higher speed RAM at higher latency.
My 1:2 and 2:3 ratios for Xeon Woodcrest was simply conjecture at this stage. Let's say you could pop in a 1066mhz FB-Dimm.
Woodcrest bus is 333mhz. If you could only run 1:1 divider, then that's
333:333 ; your RAM is only running at 666mhz effective. So here you have a 1066mhz FB-Dimm running only at 666mhz. Not making the most of your RAM sticks...!
Actually here my calculations need to be refined. I've been assuming FB-Dimms are similar to DDR2 in some way, multiplying by 2.
But I think FB-Dimms, if you say it's 533mhz or 667mhz, it is that. It's not double-data-rate like DDR, or DDR2, or DDR3s (DDR is twice the rate, DDR2 is also twice the rate, DDR3 is also twice the rate, the 2 and 3 at the end of DDR speaks of the generation of DDR, DDR3 doesn't mean 3 times the data rate).
Okay, so back to FB-Dimms. If you look at it and say it is running at 667mhz. Pop it into a Xeon Woodcrest. Bus speed is 333mhz. So actually, the bus speed to memory ratio is 1:2 , so that 333mhz : 666mhz. If the bus speed to memory ratio was 1:1 , then 333mhz : 333mhz which means your FB-Dimm was only running at 333mhz, quite a "waste" since it is rated at 667mhz.
Now, if you pop in a 533mhz FB-Dimm, you'd have to have a memory divider close to 2:3. Because 2:3 = 333: (333*1.5) = 333:500 = FB-Dimm 533mhz rate running at 500mhz.
So I have probably made a mistake in my earlier post about FB-Dimms because I was assuming they are double-data-rate which they may not be (?). Assuming they are not double-data-rate then the calculations show that to make the most of the *rated* speed of the FB-Dimm, the mobo has to adjust the memory ratio to run the FB-Dimm at the closest speed to its *rated* speed.
Conroe:
266mhz bus speed
multiplier for "effective FSB" = x4 = 1066 MT/s or just 1066 mhz
multiplier for CPU speed = eg. x10 = 2.66 ghz
multiplier for RAM speed = eg. x1.5 = 399 mhz, so 798 mhz DDR2 effective, can use 800mhz DDR2 sticks.
I was just exploring the core bus speed (before the quad pump) to memory speed ratio, which is really just talking about the multiplier for RAM speed above. On Intel systems now, apparently it can be x1.0, x1.5, etc. but *unlike AMD mobos* it cannot be less than x1.0 whereas AMD can have x0.66 x0.5 or something like that.
This is where I am going to pull out when it comes to discussing how the bus, CPU and memory channels all communicate with each other, that's way beyond my knowledge now.
So especially looking at Woodcrest Xeons and what FB-Dimms are supposed to do, I know that we are looking at the Glidewell platform which features the Intel 5000X (Greencreek) chipset, which has now support for PCI Express x16 bus required for graphics cards.
What the "bus speed multiplier for RAM speed" and FB-Dimms and overall how the bus works with CPU and RAM channels and all that, I am lost. I've edited my post on Xeon Woodcrest fsb:memory ratios to reflect that it is really, just guessing at this stage.