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 Post subject: CPU QuestionPosted: Tue Sep 18, 2012 4:15 pm
 Coppermine

Joined: Mon Oct 12, 2009 4:47 am
Posts: 686
Curious, how many MB/s does, say an AMD 3.2ghz cpu putting out? Going thru my system piece by piece and assigning MB speeds to each part. What is the typical math to figure out MB speeds for CPU's?

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 Post subject: Re: CPU QuestionPosted: Tue Sep 18, 2012 4:43 pm
 Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
Posts: 5260
It depends on what you want to know.

HyperTransport, on an AMD Bulldozer Chip, outputs at 25.6GB/s tops per direction. However, if you want to consider the lowest level possible, at the integer unit (ALU), an ass pull guess at throughput using 128-bit integers @ 3.2 GHz with an IPC of 1 would be 51.2GB/s (Bulldozer can do 4 independent memory/arithmetic operations per clock, so divide them evenly). But I don't know. There are specs about the processor you would have to know to get an answer (which we probably won't get) and it depends on the operation you're doing (floating point math takes longer, and thus, less throughput).

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 Post subject: Re: CPU QuestionPosted: Tue Sep 18, 2012 5:14 pm
 Coppermine

Joined: Mon Oct 12, 2009 4:47 am
Posts: 686
Obviously I wasn't looking for specifics. A general overall answer would suffice. Thanks.

So it's definitely in GB's/sec???

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 Post subject: Re: CPU QuestionPosted: Tue Sep 18, 2012 5:39 pm
 Clawhammer

Joined: Fri Sep 23, 2005 6:22 pm
Posts: 4406
Location: In the closet
robertco300 wrote:
Obviously I wasn't looking for specifics.

No! Actually it wasn't!

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 Post subject: Re: CPU QuestionPosted: Wed Sep 19, 2012 7:09 am
 Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
Posts: 5260
Just use https://en.wikipedia.org/wiki/List_of_device_bandwidths and call it a day.

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 Post subject: Re: CPU QuestionPosted: Wed Sep 19, 2012 5:20 pm
 Coppermine

Joined: Mon Oct 12, 2009 4:47 am
Posts: 686
kleinkinstein wrote:
robertco300 wrote:
Obviously I wasn't looking for specifics.

No! Actually it wasn't!

Sorry. It was to everyone else.

Thanks Lat! Good call with the Wiki.

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 Post subject: Re: CPU QuestionPosted: Wed Sep 19, 2012 5:35 pm
 Coppermine

Joined: Mon Oct 12, 2009 4:47 am
Posts: 686
One valueable thing I learned from the Wiki site is the conversion from bits to bytes.

Companies try to list things using Mb/s figuring the average person is reading megabytes when really it's megabits so I always wanted to know how to convert megabits to megabytes.

It seems the conversion number is about 12% meaning if a product lists something running at 10Mb which is 10,000,000 bits it converts to about 120,000 bytes.

Why is any of this a big deal? In the old days it was only bytes, kilobytes then megabytes. Someone in someone's marketing department figured out their products they were hocking would "appear" to run faster than they do if they listed them in bits instead of bytes. Smart idea really, giving the products' operating speed a 10 fold bump (hoping people would not realize the difference between bits and bytes).

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 Post subject: Re: CPU QuestionPosted: Wed Sep 19, 2012 6:29 pm
 Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
Posts: 5260
The same reason why screens are marketed with "dynamic contrast ratio". Allegedly some cheap ass companies were finding something to inflate their specs, and if the other big companies didn't do the same, they'd look like crap in comparison. Dynamic contrast ratio is just some fabricated spec.

Also, in the end, your usable bandwidth for actual data is different. For instance, SATA3 has a bandwidth of 6Gbps. If you divide this by 8 (8-bits a byte), you should get like 750MB/s. However, you actually only get 600MB/s, because SATA uses 8b/10b encoding. So right off the bat, you lose 20% of your usable bandwidth.

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 Post subject: Re: CPU QuestionPosted: Wed Sep 19, 2012 8:53 pm
 Willamette

Joined: Thu Aug 12, 2004 9:04 am
Posts: 1035
Which is correct as the original SATA spec debuted at 150 MB/s, SATA II was to be 300 MB/s, and SATA III was to be 600 MB/s. No real loss at all.

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