maybe a stupid question but.....

chanratt

this may seem like a stupid question to some but there is something that is confusing me, so much so that my query itself may seem confusing........I'll try anyway.

Is there any correlation between the amount of bits a component can produce and the amount of physical pins it has....example..my 184pin memory stick is capable of storing 128mb of ram. On a pci expansion bus with 32 bits (4 channels) does that mean it has 4 'physical' wires to travel through? Does a 32bit address bus have 4 visible channels?

I hope my question makes sense

OoteR

chanratt wrote: »

this may seem like a stupid question to some but there is something that is confusing me, so much so that my query itself may seem confusing........I'll try anyway.

Is there any correlation between the amount of bits a component can produce and the amount of physical pins it has....example..my 184pin memory stick is capable of storing 128mb of ram. On a pci expansion bus with 32 bits (4 channels) does that mean it has 4 'physical' wires to travel through? Does a 32bit address bus have 4 visible channels?

I hope my question makes sense

Not a stupid question, and i'm not sure i'm entirely right either.. someone better can probably clarify.

Now, the size limits on say your ram compared to the pins out are not necessarily correlated. You have a 184pin stick of memory that holds 128MB of ram, but it could just as well hold 64MB, 256MB, 512MB etc etc.

The size of the BUS has (almost) nothing to do with that. The Bus is your interconnect between different devices. A bus's measurement (32bit in the PCI case) means that 32 bits can move in parallel between the two connected devices, I believe per clock cycle (Mhz, Ghz). Modern PCI (not PCI-E, PCI-X etc, those are their own spec) bus's are 66 or 33 Mhz. The bits*Mhz will give you your 'bandwidth' per second, the total amount of data that can be moved from device to device.

Ok, so - 32 bits in a bus sense means that 32 bits can be moving in parallel. That means that at any given time 32 bits can be going to/from the PCI device (in theory).

So the raw speed potential (i believe) is calculated something like:

66,000,000 * 32 = 2112000000 Bits/Second

2112000000/8 = Bytes/Second = 264000000
264000000/1024 = KB/Second = 257812.5
257812.5 /1024 = MB/Second = 251.77001953125
251.77001953125/1024 = GB/Second = 0.245869159698486328125

Back to your ram - the limit on your ram size has more to do with the CPU's architecture than it does with the simple 'wires' that are connecting the ram/cpu/video/etc. A 32 bit CPU can only address up to a 32 bit address space of memory without some tricks (not getting into it). It doesn't know how to see beyond that limit. A 64 bit address space is immensely larger, that is how a 64 bit cpu can address (in hardware.. as i said before, not getting into the fun tricks) a much larger amount of memory.

Your 184 pin memory is actually on a 64 bit bus.

This is a quote from wikipedia:
-=-=
With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) x 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.
-=-=-
DDR SDRAM - Wikipedia, the free encyclopedia

Follow that link to wikipedia, and it explains more about ram bandwidth.

Hopefully I didn't confuse you more... You need to look up Mhz, etc and learn more about that stuff on your own. Good luck!

chanratt

OoteR wrote: »

Not a stupid question, and i'm not sure i'm entirely right either.. someone better can probably clarify.

Now, the size limits on say your ram compared to the pins out are not necessarily correlated. You have a 184pin stick of memory that holds 128MB of ram, but it could just as well hold 64MB, 256MB, 512MB etc etc.

The size of the BUS has (almost) nothing to do with that. The Bus is your interconnect between different devices. A bus's measurement (32bit in the PCI case) means that 32 bits can move in parallel between the two connected devices, I believe per clock cycle (Mhz, Ghz). Modern PCI (not PCI-E, PCI-X etc, those are their own spec) bus's are 66 or 33 Mhz. The bits*Mhz will give you your 'bandwidth' per second, the total amount of data that can be moved from device to device.

Ok, so - 32 bits in a bus sense means that 32 bits can be moving in parallel. That means that at any given time 32 bits can be going to/from the PCI device (in theory).

So the raw speed potential (i believe) is calculated something like:

66,000,000 * 32 = 2112000000 Bits/Second

2112000000/8 = Bytes/Second = 264000000
264000000/1024 = KB/Second = 257812.5
257812.5 /1024 = MB/Second = 251.77001953125
251.77001953125/1024 = GB/Second = 0.245869159698486328125

Back to your ram - the limit on your ram size has more to do with the CPU's architecture than it does with the simple 'wires' that are connecting the ram/cpu/video/etc. A 32 bit CPU can only address up to a 32 bit address space of memory without some tricks (not getting into it). It doesn't know how to see beyond that limit. A 64 bit address space is immensely larger, that is how a 64 bit cpu can address (in hardware.. as i said before, not getting into the fun tricks) a much larger amount of memory.

Your 184 pin memory is actually on a 64 bit bus.

This is a quote from wikipedia:
-=-=
With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) x 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.
-=-=-
DDR SDRAM - Wikipedia, the free encyclopedia

Follow that link to wikipedia, and it explains more about ram bandwidth.

Hopefully I didn't confuse you more... You need to look up Mhz, etc and learn more about that stuff on your own. Good luck!

thanks ooter. no you didn't confuse me more, but I will have to read this a couple of times so it will sink in, like most of the new A+ edition I got for xmas. I'm just glad that I wasn't asking a stupid question lol. But thank you for taking the time to explain all of this. I have a basic grasp of bus width, MB/s, throughput etc, but atm all the terms are floating around my head right now waiting for me to tie them all together.