Memory

ConUladh

Besides the standard PC100/133 SDRAM DIMM stuff what do I need to know when looking at details of memory I'm going to buy

What do the following mean ?

7 ns Speed

32M x 4 Configuration (or 32 x4)

3.3V Non-Registered

CAS 3

Anything I should stay away from?

Thanks

Joe22

3.3V is 3.3 volt (as far as i know)

Cas is latency (so 2 would be better then 3)

i dont really know the difference between

buffered and Non-Registered

32M x 4 Configuration, just the way its arranged on the stick

7 ns Speed (NOW IM ONLY GUESSING HERE)
but id say that means it take 7 clocks for it to get the data.
i havent seen that before.

hopes this helps

Moriarty

7ns (nanoseconds) is the time it takes for the ram to respond (?). Lower the better, anyway.

---

Moriarty
mrmoriarty@eircom.net

Joe22

thats pretty much what i thought,
i havent seen it in spec for memory before.
whats the normal amount for say p133 cas 2

[This message has been edited by Joe22 (edited 09-05-2001).]

Kali

I've probably mentioned this before..
but theres a very indepth article on memory latency at:
http://www.aceshardware.com/Spades/read.php?article_id=5000186 if anyone is interested in that side of things.

Refering to the 7ns speed its the CAS latency + RAS latency + 1 cycle to transfer the data... of course theres the added latency between chipset/FSB/CPU before you get an overall latency time.

CAS (Column Access Strobe, just looked that up now ) latency refers to the time taken to access a particular column address within the memory bank.

davoc

as regards non-registered and buffered, im pretty sure that buffered memory does a second check on info that passes through it to insure no mistakes are made.
mainly for use in servers i think
non registered stuff is for your regular hone pc.
i think

ConUladh

Excellent, thanks

None of it is anything I need worry about too much when buying for a home PC is it? (I mean for example CAS of 3 rather than 2 wouldn't be a diaster of a compromise)

Is voltage an issue?

Joe22

actually, alot of people think cas is pretty important, even more so then your fsb,
ive seen bendmarks once were cas2 pc100 performed allmost as good as cas 3 pc 133.
for like £3 extra id go for it
as for voltage, no its not important unless you plain to overclock you memory,

Kali

For a home PC go for the cheapest RAM you can find with a brand name, it should perform without any big difference for the majority of appplications.

Just to add an example (of unbranded ram).. I got a drop of 12fps in Q3 when I exchanged the RAM i have in my own PC (standard Gateway stuff, actually quite decent RAM, not sure of the timings offhand) for unbranded, secondhand CAS3 (10ns iirc) ... quite a substantial drop in performance.

Edit: just as well.. I added the secondhand cas3 stuff to the machine to make 256mb, and even that decreased performance by 6fps despite the extra 128... Be wary

[This message has been edited by Kali (edited 09-05-2001).]

Joe22

i think gateways memory is made by pc
not a bad make buts its not curcial
they changed about 2 years agoso i dont know what way it is now

Leverz

What you want is CAS2 PC133 its cheap and worth is, Crucial Memory are a good manufacturer. The voltage is only important if you are going to be over-clocking your system.

_CreeD_

Getting quality Ram also helps when dealing with the more advanced memory-access options available in today's controllers.

Take the ABIT kt7a as an a example, it's got loads of options for timing/interleaving etc. With an old stick of 'PQ' 133 ram in my system I couldn't use most of them, it was too unstable, switching them all to Crucial allowed every setting to be maxed.

Definitely go with Cas-2 if you play games, they tend to need lots of smaller files very quickly, benefitting more from fast access than larger bandwidth (usually...depends on how texture heavy the game is).

sutty

Voltage is important. If your system is a old (about 3-2 years old), it could use 5 volt SDRAM. If you where to put a 3.3 volt stick in it may blow the RAM. As above CAS2 is better than 3 if you play games, I think its also better for Graphic rendering (not sure on that on) 7ns is the timing (I dont know how joe has never seen that before, Its on every stick's stats and in the BIOS)

RAM at the moment is very cheap, so you can go out and buy the best brands

infineon.
Crucial.

are but two. Also remember what type of RAM you use, theres a lot of different ones out there. 486, EDO, SDRAM, RDRAM, DDR.


Good luck in finding waht you want

---

Ciaran Sutcliffe
aka: sutty
[HIV]sutty
For a good time goto:
http://www.hotinternetvirgins.com

Joe22

my bios is a pos, doesnt tell me anything,
and as for spec, you would be surprised how many makes its not on, the stuff i bought only had Pc 133, didnt even have what cas it was on it
but about voltage, if a machine is that old wouldnt he be looking for 4mb-8mb sticks of ram, like an old compaq 90(about 4 years back) wont handle anything over 8mb sticks

and Leverz didnt i just say what you said? maybe you should read a post before you reply

Gerry

7ns ram is usually rated at 133mhz cas2. It depends on whether they are lying to you in the specs or not. Most pc133 cas3 ram is 7.5ns. Pc100 cas2 is 8ns, pc100 cas3 is 10ns.

So I dunno if the ram you looking at is actually 7ns ram. A common problem is if the ram chips are marked with a trailing 7, the vendor sells them as 7ns ram.

3.3v is standard for sdram, 5v EDO dimms are non existant, and were always quite rare, mainly being used in pentium pro's, and laptops. They wouldnt fit in a standard 168 pin dimm socket anyway.

non-registered implies that the memory is not ECC, which means that the memory does not perform any error checking, ECC ram has an extra chip which computes the parity for the other chips, allowing single bit errors to be detected and corrected. Errors in ram are very rare, so only mission critical machines like servers need ECC.

registered dimms also have extra delays when they are read from and being written to. This helps reliability, but slows them down.

So unregistered dimms are what you want.

You should stay away from cas3, similar to kali, I have seen a 10% fps boost on a machine in games, just by changing the bios cas setting from 3 to 2. If your bios allows you, you should set the ras-to-cas time to 2 also, along with the ras precharge time. (if you have cas2 ram of course.)



[This message has been edited by Gerry (edited 10-05-2001).]

WhiteWashMan

<font face="Verdana, Arial" size="2">Originally posted by davoc:
as regards non-registered and buffered, im pretty sure that buffered memory does a second check on info that passes through it to insure no mistakes are made.
mainly for use in servers i think
non registered stuff is for your regular hone pc.
i think </font>

isnt that edo ram?
does a parity check on the information being transfered. slows it down by about 3-4% nothing to worry about really, but it is used on servers mostly.
of course, could be talking a complete load of old tosh....

Gerry

buffered=registered.

a load of registers hold the info when the memory is being read from and written to. This gives the memory more time to do these operations, making it more reliable.

Parity memory is like ECC memory, except it doesnt correct errors.
I.E for every 8 bits of ram, there is an extra bit which holds the parity of the other 8 bits. If the ram is even parity,

and you have 10000000 in the 8 bits

the parity bit will hold a 1

this makes the amount of 1's equal to 2 which is even. etc,etc

so if an odd number of 1's is detected after a write to memory, or a read from it, the memory controller knows something is up. With parity ram, it just hangs the machine, to stop the errors propogating.

ECC holds more information on the parity, and it can isolate single bit errors, and correct them, so the machine works away as normal. I think it does this through hamming codes. If more than 1 bit is wrong though, it fails.

EDO ram usually does not have parity.
You can tell parity/ECC ram by whether there is a 64 or a 72 in its specs. for example 8M * 72 or 8M * 64. The 72 means its parity/ECC.

ConUladh

Thanks for the help

If unbranded memory is going really cheap should I go for it? How dodgy is it?

Gerry, CAS wasn't included in the spec I was looking at but I'd seen it around so I appended it on the end for the purposes of my query

Joe22

ConUladh you want to find that out
and gerry nice lay out, wish i knew you two months ago, i found out about cas the hard way

WhiteWashMan

<font face="Verdana, Arial" size="2">Originally posted by Gerry:
buffered=registered.

a load of registers hold the info when the memory is being read from and written to. This gives the memory more time to do these operations, making it more reliable.

Parity memory is like ECC memory, except it doesnt correct errors.
I.E for every 8 bits of ram, there is an extra bit which holds the parity of the other 8 bits. If the ram is even parity,

and you have 10000000 in the 8 bits

the parity bit will hold a 1

this makes the amount of 1's equal to 2 which is even. etc,etc

so if an odd number of 1's is detected after a write to memory, or a read from it, the memory controller knows something is up. With parity ram, it just hangs the machine, to stop the errors propogating.

ECC holds more information on the parity, and it can isolate single bit errors, and correct them, so the machine works away as normal. I think it does this through hamming codes. If more than 1 bit is wrong though, it fails.

EDO ram usually does not have parity.
You can tell parity/ECC ram by whether there is a 64 or a 72 in its specs. for example 8M * 72 or 8M * 64. The 72 means its parity/ECC.</font>

that is course, when i say edo, what i mean to say is ecc
bugger. damn yankies!