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Quad-pumped P4 Bus = higher mem speeds

Last response: in CPUs
a b à CPUs
November 12, 2000 9:52:57 AM

The P4's frontside bus is clocked at 400MHz, or 100MHz at 4 instructions per cycle. This is surely the same technology used in DDR but doubled again? Does this mean we could soon see memory running at 4x133MHz, or 533MHz? That would be *kewl*.
November 12, 2000 11:54:20 AM

Yeah that kinda confuses me too. But since DDR has just been launched, it is understandable that the technology will be obselete in a year (and then qdr take over) because we all know ram is the slowest evolving technology inside the computer case, besides monitor, mouse and keyboard.

Smart guys are not smart; they only see things in different perspective.
1st <b>member</b>!
a b à CPUs
November 12, 2000 1:34:33 PM

i belive DDR-II is what u're looking for.
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a b à CPUs
November 12, 2000 2:12:54 PM

The Pentium 4's FSB works in a similar way to AGP 4x speed. It uses 2 signal strobe lines, each running at 100Mhz DDR, so the memory bus will still operate at 100Mhz. Remember that the FSB operates between the CPU and the memory controller within the Northbridge chip. Depending on what memory is being used, the controller will either operate synchronously with the FSB (as with SDRAM and DDR SDRAM) or asynchronously (as with RDRAM).
a b à CPUs
November 12, 2000 3:19:19 PM

The problem will probably be to find the memery needed to go a this speed, and it about the same as amd 200mHz bus, it took 100mHz ram for quite a while and now its about to take 133ddr. The only thing it says is that the information will travel fast between the cpu and chipset.

(c) DarkGuard 2000
a b à CPUs
November 12, 2000 4:33:13 PM


Look for a major step in the memory field. This is whats going to hold the processor developments to a degree. Memory bottlenecks have always plagued chip design, and are starting to really come into effect now. Look at both processors and video cards. Nvidia has squeezed just about all they can out of memory, and the bottle necks still prevent even faster speeds.

Timothy Stankus
One of the First AMD Athlon Users =)
a b à CPUs
November 13, 2000 1:17:44 AM

As mentioned by other posters the answer is YES there very well could be 400MHz memory. And YES there very well could be QDR-SDRAM (quad data rate). But for now, the Pentium IV 400Mhz bus is *just* the bus speed and is meant to be connected to PC800 RDRAM which is iactually just 400Mhz Rambus memory running a DDR 8-bit serial memory bus hcih is equvalent to 16-bit memory running over a 400Mhz serial bus. DDR-SDRAM is 64-bit memory running on a double pumped data bus. The problem with having QDR-SDRAM is that nobody even comes close to making DRAM cells fast enough to run over a synchronous 400Mhz bus. So while the bus speeds are available now, actual memory (other then RamBus memory) that runs that fast is still quite a ways off.

** Nothing In Spec Inside
June 19, 2001 9:47:30 PM

Wow...these were the days.
The ignorance (and therefore bliss) of youth.

Apple? Macintosh? What are these strange words you speak?
a b à CPUs
June 19, 2001 10:04:08 PM

Intel uses RDRAM to hold up to those data rates, and is pushing for 200MHz bus (400MHz DDR) DDR ram. Why they don't simply go for the existing QDR technology is beyond me. As far as I know they are still trying to renegotiate with Rambus, so fast DDR for the P4 will probably have to wait until next year.

Cast not thine pearls before the swine
June 19, 2001 10:12:49 PM

"because we all know ram is the slowest evolving technology inside the computer case, besides monitor, mouse and keyboard."

Hey, what about floppy drives?

/ Topaz
June 20, 2001 12:43:00 AM

cdburrners are still to exspensive for everybody just to get one
because that you have to bassically get a floopy with every thing

i would like to have a hardive that is much faster then memory at this time becuase that is the true bottle knick of a commputer know in days
a b à CPUs
June 20, 2001 12:47:58 AM

cdburners are dirt cheap........ only the best ones are expensive
June 20, 2001 5:38:17 AM

What you takl is pc 1066 who is 133*4.That already exciste.
June 20, 2001 7:52:57 AM

the P4 bus is still 100 MHz, and its DUAL channel, that means you must have two RIMMS, one for each channel to be able to allow independent simultaneous access to different blocks of ram. then each channel is dual pumped that makes the *effective* frequency of 400 MHz. Using a 133 MHz real FSB will give 533 MHz of *effective* FSB.

BTW that doesnt mean 4 instructions per clock, it means its able to access memory at these speeds. talking of instructions per cycle, P4 can handle upto 20 instructions at a given time in its 20 stage hyperpipeline and execute 4 instruction per cycle *provided they are all integer and independent of each other*

the question is, with all these heavy memory bandwidth, does the P4 live upto this speed? in early times, cpu needed higer mem bandwidth, and now with bandwidths of the order of 3.2GBps, is the CPU really ready for such speed?


<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>
June 20, 2001 3:31:53 PM

Wow, I can't believe I actually revived a thread that's several months old :) 

Apple? Macintosh? What are these strange words you speak?
a b à CPUs
June 20, 2001 3:44:40 PM

its a good thread... died too young <smiles>

The hard disk is the biggest bottleneck (aside from the floppy, which rarely used) with ms rather than ns access times. Solid state drives are the obvious solution.

Next i'd say is the PCI bus; its already at saturation level in most cases. 64bit and 66Mhz just aren't making an impact in desktop mobo technology, which is a shame... Its a proven technology in servers, though so when the average consumer NEEDS it, I'm sure they'll get it. Hot plug PCI sure is useful too...
June 20, 2001 4:25:27 PM

no QDR... SDR (standard ram) = single data rate DDR = dual/double date rate QDR = quad/quadruple data rate...

you do not strengthen the weak by weakening the strong