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166MHz system bus in TiBook and 400MHzbus in P4

cb911

cb911

macrumors 601
Original poster
Mar 12, 2002
4,134
4
BrisVegas, Australia
i was just wondering about the difference between the TiBooks system bus and a P4s system bus. i don't know much about this sort of stuff, so correct me if i'm wrong.
is the reason for having a 166MHz bus because the current RAM can't keep up? if the TiBook had a faster system bus, would spend time waiting for the RAM? and if current RAM isn't that fast, why does the P4 have a 400MHz system bus? wouldn't the CPU just spend time waiting for the RAM to refresh?:confused:
 
Well for starters, the Tibook uses a 133Mhz bus, not 166Mhz!

Technically speaking, the chipsets used by the P4 only have a 100Mhz clock speed. What happens is data is transfered four times on each bus clock, which intel calls a 400Mhz system bus.

Whilst using SDRAM, it's not going to be possible to increase the speed of the system bus on any of the macs. That's why virtually everyone who uses macs is hoping that apple are going to switch to DDR sometime in the near future. The CPU is not the bottleneck in current systems, so a faster system bus would certaintly improve the performance of the computer.

As for whether we'll be seeing DDR in the tibooks anytime soon, i'm not betting on it. I believe DDR runs hotter than SDRAM; as if the tibooks didn't run hot enough already :p As ever though, one can dream :)
 
whoopsie! i don't know how i could have made the mistake about the TiBook actually having a 133MHz bus. i guess thats just my wishful thinking! thanks for the info about the P4. i was looking but i couldn't find anything.
 
You all have to understand a vast difference in the archutechtue of the processors, PowerPC vs. x86. for every like 5Mhz on a PowerPC its equalent to 10Mhz On a PC, so what I think that would even it out.
 
To the contrary..

DDR RAM actually runs cooler and uses less power than SDRAM.. newer technology =)
 
Originally posted by TiMacLover
You all have to understand a vast difference in the archutechtue of the processors, PowerPC vs. x86. for every like 5Mhz on a PowerPC its equalent to 10Mhz On a PC, so what I think that would even it out.
Click to expand...

But DDR in effect doubles the speed. So while a P4's bus may be only 200MHz, it's running both ways simultaneously so therefore it's 400MHz. So suppose you're right about the 1:2 ratio comparing PowerPC MHz with Pentium MHz. Even so, the DDR comes out a little under twice as fast!

Apple's WAY behind in this department any way you look at it.
 
Re: To the contrary..

Originally posted by Funkatation
DDR RAM actually runs cooler and uses less power than SDRAM.. newer technology =)
Click to expand...

it's good to have someone to correct mistakes :)
 
The busses on macs wont get quicker until the G4 is revised. At the moment, it is limited to 133Mhz (I think). The summer revisions of macs will probably get the new motherboards to allow this.
 
Apple will most likely upgrade the G4 with DDR. In which case, I'm getting one!
 
Yes they will update to DDRAM, BUT, if the powerbook is not updated to DDRAM in this revision we will have another 6 months before the next revision. That is not good.
 
Intel's "400MHz" bus uses RDRAM. Technically, It is actually two double-pumped 100MHz buses 90 degrees out of phase with each other that act as one bus, making it the equivalent of a quad-pumped 100MHz bus.

Intel's "400MHz bus" can push up to 3.2GB/s max, whereas Apple's 133MHz bus can push up to 1GB/s max... so even if Apple's processor can do more each clock cycle, that just means Apple's processors are going to be sitting around waiting longer for data from the memory.
 
Originally posted by PCUser
Intel's "400MHz" bus uses RDRAM. Technically, It is actually two double-pumped 100MHz buses 90 degrees out of phase with each other that act as one bus, making it the equivalent of a quad-pumped 100MHz bus.

Intel's "400MHz bus" can push up to 3.2GB/s max, whereas Apple's 133MHz bus can push up to 1GB/s max... so even if Apple's processor can do more each clock cycle, that just means Apple's processors are going to be sitting around waiting longer for data from the memory.
Click to expand...



Not all of the P4's use RDRAM. Most of the "value" P4 PC's use SDRAM as well, and there are various chipsets by Intel, VIA and SiS that use DDR RAM, and intel is also developing a Dual DDR chipset as well that will hopefully dethrone the RDRAM chipset. You will only find RDRAM in a very high end P4 PC as it is still very expensive compartively to other types of RAM, even though the performance gains are not that much better... and there have been tests showing DDR400 to be faster than a dual channel RDRAM solution.
 
I stand corrected... I did not realize that DDR400 had finally been released to the general public. There are two ways to get Intel's "400MHz" bus, and more to come soon, then.
 
Originally posted by PCUser
Intel's "400MHz" bus uses RDRAM. Technically, It is actually two double-pumped 100MHz buses 90 degrees out of phase with each other that act as one bus, making it the equivalent of a quad-pumped 100MHz bus.

Intel's "400MHz bus" can push up to 3.2GB/s max, whereas Apple's 133MHz bus can push up to 1GB/s max... so even if Apple's processor can do more each clock cycle, that just means Apple's processors are going to be sitting around waiting longer for data from the memory.
Click to expand...

But how many PC laptops are using this technology?
 
None that I've been able to find. :) When I was talking about the 400MHz bus, I was simply trying to clear up any misunderstandings about Intel's 400MHz bus (and learned something new in the process...).

Most P4-M laptops I've looked at recenlty (Gateways, Dells, Compaqs, and IBMs) use PC133 SDRAM (Same as Apple) or use DDR266.

Edit: To my surprise, I found a PC laptop that supposedly uses DDR400 (the Dell Latitude C840): http://www.dell.com/us/en/biz/products/series_latit_performance_notebooks.htm. However, I have to question that one, because DDR2100 is 266MHz, not 400MHz. I think someone must have entered one of the numbers (DDR2100 or 400MHz) wrong. ;)
 
Originally posted by PCUser
None that I've been able to find. :) When I was talking about the 400MHz bus, I was simply trying to clear up any misunderstandings about Intel's 400MHz bus (and learned something new in the process...).

Most P4-M laptops I've looked at recenlty (Gateways, Dells, Compaqs, and IBMs) use PC133 SDRAM (Same as Apple) or use DDR266.

Edit: To my surprise, I found a PC laptop that supposedly uses DDR400 (the Dell Latitude C840): http://www.dell.com/us/en/biz/products/series_latit_performance_notebooks.htm. However, I have to question that one, because DDR2100 is 266MHz, not 400MHz. I think someone must have entered one of the numbers (DDR2100 or 400MHz) wrong. ;)
Click to expand...

Ah it's all such fun, the march of progress:)
Even cheap Powerbooks and PC laptops now have more processing grunt than desktops of a few years ago.
We live in interesting times - hmm, sounds like a Chinese curse.
 
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