Wandwidth???

[bighead111]

Sorry Bandwidth I meant! not Wand

I always forgot how to work out the bandwidth

Is it like this: Mhz X Bits = MB/s? Please someone correct me if this is wrong. Thanks

<P ID="edit"><FONT SIZE=-1><EM>Edited by bighead111 on 05/15/02 09:58 AM.</EM></FONT></P>

 

[FatBurger]

No

<font color=blue>Hi mom!</font color=blue>

 

[eden]

damn you bandwidth hog!! Shoo!

--
Intel had 2.2GHZ Willies left...I bought one, it powered my entire neighborhood!

 

[eden]

BTW I think you take the single SDR MHZ of the mem core and yes, multiply by BYTES not bits. So if the mem core of a Parhelia 512 is 300MHZ SDR (600MHZ DDR), you take the 512-bits=64bytes, and do the calc. It gives 19200, rounded to 20GB as they claim.

--
Intel had 2.2GHZ Willies left...I bought one, it powered my entire neighborhood!

 

[HolyGrenade]

Actually its bus is 256bits. You multiply the bus speed with the DDR speed. The matrox marketing were just trying to be clever and double the number on the box. In any case it will come out with the same value.

the formula is

<b>bus frequency * bus width / 8</b>


and double the result if its using DDR. I'll have to tell you though, outside the labs, in the real world this figure doesn't hold much water.

<font color=red><b>A man is only as old as the woman he feels</b></font color=red>

 

[eden]

Hmmmm...well it is DDR 512, don't forget. So this is why I said 64-bit instead. Also your way confuses me! Which bus speed? Anyway to me, it's easier starting with bytes, and multiplying by the SDR mem. That way you reach faster the real bandwidth.

--
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[HolyGrenade]

What you've done is just doubled the bus width because it is using ddr. Thats how you got 64. But in actual fact the bus width remains the same. Its easy enough to get the the bytes xfered in one go by just dividing the bus width by 8.

ps. As I was posting the last one, I realised I wrote bus speed instead of bus frequency, So I changed it straight away. But I suppose you must've got to the thread in the tiny window of time.

<font color=red><b>A man is only as old as the woman he feels</b></font color=red>

 

[eden]

Well in any case, we both get 19200MBs/sec, so it doesn't matter which way works. I prefer mine because it's shorter to me.

--
Luke, I am your father...but due to a bacon-slicing accident, your mother... :lol:

 

[chuck232]

Both ways get you the same answer, but the Parhelia is only 256bit DDR, which is 512bit SDR.

My firewall tastes like burning.

 

[eden]

Um DDR doesn't double slow rate! :lol:
You probably meant 512bit DDR, just like DDR266MHZ, not DDR133.

--
Luke, I am your father...but due to a bacon-slicing accident, your mother... :lol:

 

[xxsk8er101xx]

it's megaherts * the data path in bytes. Well it works for stuff that doesn't use special technology to cheat for it's bandwidth.

SO if you take pc800 and multiply it by the databit path in bytes you get 800 x 2Bytes (16bit datapath) and thats your bandwidth. which is 1600MB/s. Thats if you don't use dual channel .. obviusly dual channel doubles the bandwidth.

samething with anything else ... Take the AGP bus of 4x which is 2^26 (66mhz) * 4x * 4Bytes (32bit datapath) = 1,073,741,824 B/s.

PCI bandwidth, take 2^25 (33mhz) * 4Bytes (32bit datapath) = 134,217,728 B/s

However you have to think of other technology involved too and find out what that does .. such as vlink .. .to be more accurate with current technology. to get the right bandwidth.

take PC2100, 2^28 (266mhz) * 8Bytes (64bits) = 2,147,483,648 (thats your PC2100) B/s OR 17,179,869,184 b/s if you multiplied it by bits instead. As you can see multiplying it by the bits gives you bandwidth in bits.

Lower case b always stands for bits uppercase B always stands for Bytes.

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[HolyGrenade]

God a lot of confusion going on here...

266MHz DDR is a loosly correct term as it data is transferred twice every clock tick.

512bit DDR (for a 256bit bus) is an incorrect term, as Doubling the data rate will have noeffect on the bus width. If the bus is 256bit (32 byte), it remains 256bit. However, the data transferred actross the bus every clock tick is doubled.

<font color=red><b>A man is only as old as the woman he feels</b></font color=red>

 

[chuck232]

Like I said basically, isn't the Parhelia 256bit DDR which is basically equal to 512bit SDR?

My firewall tastes like burning.

 

[HolyGrenade]

You don't usually associate the bus width with the data rate in that way. But if your saying that a something with a 256bit data bus running using ddr would result in the same performance if it were given a 512bit datapath instead and switched to SDR, while keeping the actual frequency the same. Then, the answer is: theoretically yes.

<font color=red><b>A man is only as old as the woman he feels</b></font color=red>