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Memory Question

P

paruhd0x

Diamond Member
What's the difference between non-parity and parity and what is ECC?

What is the best 256MB stick of ram on this page?
Link

Thanks 🙂
 
I believe that non-parity is slightly faster than ECC (parity), but ECC is more stable because it does error correction (hence the reason its slower but more stable). People usually buy the ECC for workstations while most folks get the non-parity for PCs.

The second on the list is the best. PC1600 runs at 100mhz x2. PC 2100 runs at 133mhz x2

The CAS (collumn access strobe) ratings aren't displayed though. CAS 2 is better than CAS 3. Perhaps all DDR is CAS 2? I'm not sure.

Hope this helps
 
How much slower is ECC compared to non-parity? Is it a noticable difference? Stablility is a good thing, if the speed is almost the same.
 
Hardly noticeable, but the stability doesn't make a huge difference either. However, ALL of your RAM (from what I've read) has to be ECC for it to work.
If you like to tweak i.e. overclock etc. then the added stability of the ECC will be negligible. Most folks in this forum tweak to the limit: they overclock their CPUs, video cards, have their hard drives in RAID 0,... and they still run fairly stable.
So which RAM you buy doesn't make much difference, but if you like to tweak, maybe you want to squeeze that extra 0.005% out of your system.😉
 
Parity:

"Parity (parity bit)is used sn additional binary digit, it is added to a group of bits that are moved together. This bit is used for identifying whether the bits being moved arrived successfully. Before the bits are sent, they are counted and if the total number of data bits is even, the parity bit is set to one so that the total number of bits transmitted will form an odd number. If the total number of data bits is already an odd number, the parity bit remains or is set to 0. At the receiving end, each group of incoming bits is checked to see if the group totals to an odd number. If the total is even, a transmission error has occurred and either the transmission is retried or the system halts and an error message is sent to the user."

ECC

"1. When a unit of data (or "word&quot😉 is stored in RAM or peripheral storage, a code that describes the bit sequence in the word is calculated and stored along with the unit of data. For each 64-binary digit word, an extra 7 bits are needed to store this code.

2. When the unit of data is requested for reading, a code for the stored and about-to-be-read word is again calculated using the original algorithm. The newly generated code is compared with the code generated when the word was stored.

3. If the codes match, the data is free of errors and is sent.

4. If the codes don't match, the missing or erroneous bits are determined through the code comparison and the bit or bits are supplied or corrected.

5. No attempt is made to correct the data that is still in storage. Eventually, it will be overlaid by new data and, assuming the errors were transient, the incorrect bits will "go away."

6. Any error that recurs at the same place in storage after the system has been turned off and on again indicate a permanent hardware error and a message is sent to a log or to a system administrator indicating the location with the recurrent errors."


/B
 
I wouldn't bother paying extra for the ECC as long as the non-parity is okay with the motherboard ( there are new ones coming out that require ECC) not all DDR is CAS 2. I think the CL=2 is the cas latency number on that page, but I am not sure why all the PC 2100 is CL=2.5 and the PC 1600 is the CL=2. If it was me, I would buy the second one down from the page that you linked to.
 


<< So buying ECC RAM for a personal pc is overkill? >>



Definitely! Just go with the standard, NON-ECC, NON-Parity, unbuffered memory.

/B
 


<< Just go with the standard, NON-ECC, NON-Parity, unbuffered memory >>


yes &amp; save a few bucks from not getting the ECC ram!
 
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