morpheus30
asked on
Types of RAM
I recently added memory to a Pentium 3 system for my boss. I purchased a 256 MB PC-133 RAM Chip and it worked just fine. But then I tried to add the SAME type of RAM to another Pentium 3 system but it didn't work. I found out that it took PC-100 RAM Chips. Why is this? I thought the type of memory you put in a system depended on the Processor you have; i.e.:
Old Petium = EDO
Petium MMX = PC -66
Pentium 2 / Celeron = PC-100
Pentium 3 = PC-133
I also found that my boss' computer also worked with PC-100 RAM chips, but this doesn't surprise me as much. Can someone please give me a rule of thumb of the kinds of memory out there and what types of systems use them. I also want to know the difference between ECC and non ECC memory and why it makes a difference? And I also want to know about the RAMBUS hype of a few years ago. Is that the FASTEST memory chip out there?
I will double the points if you come up with a thourough answer...
Old Petium = EDO
Petium MMX = PC -66
Pentium 2 / Celeron = PC-100
Pentium 3 = PC-133
I also found that my boss' computer also worked with PC-100 RAM chips, but this doesn't surprise me as much. Can someone please give me a rule of thumb of the kinds of memory out there and what types of systems use them. I also want to know the difference between ECC and non ECC memory and why it makes a difference? And I also want to know about the RAMBUS hype of a few years ago. Is that the FASTEST memory chip out there?
I will double the points if you come up with a thourough answer...
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Also, if you put a 133 module in with a 100, it will usually work but at the reduced speed of 100. It's best practice however not to mix modules.
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Regarding ECC: ECC stands for Error-Checking & Correction. It is most often used in server or high-end workstation environments.
In a nutshell, if you need to find out if you have/need ECC, parity, or non-parity memory, count the number of chips on the module. If you can evenly divide the number of chips by three or five, the module is ECC or parity, if not, then it is a non-parity module. Then look at the part numbers on the chips of your module. If each chip has the same part number, you have ECC. If one chip is different, you have parity.
ECC stands for "Error Checking and Correction". It's a technology that allows the memory to not only detect memory errors but also correct them on the fly.
Some of us who have been around computers longer may remember the old parity memory that used to be on sale at a slight premium over regular memory. ECC and Parity memory share some likeness in that both can detect errors in the memory, however, ECC takes it one step further by correcting the error and preventing it from affecting your application.
As I mentioned, ECC is something only a server or mission critical system would need (sort of like Registered Memory) because memory errors are very rare and because the number of errors likely to be experienced by a system is proportional with the amount of RAM on that system - since servers tend to have a few Gigabytes of memory, and because they are on 24hours a day and also deal with huge amounts of pretty important data, it's not hard to figure out why ECC is considered a must for any serious server application.
ECC Slows down Boot time too. Another reason why you wouldn't want ECC in a regular system is because once ECC checking is enabled you better be prepared for the longest RAM check you've ever seen in your life. It is literally several times slower than regular memory checking during POST.
Also of note, because of the way ECC works, you can expect it to perform roughly 2% slower than non-ECC memory.
In a nutshell, if you need to find out if you have/need ECC, parity, or non-parity memory, count the number of chips on the module. If you can evenly divide the number of chips by three or five, the module is ECC or parity, if not, then it is a non-parity module. Then look at the part numbers on the chips of your module. If each chip has the same part number, you have ECC. If one chip is different, you have parity.
ECC stands for "Error Checking and Correction". It's a technology that allows the memory to not only detect memory errors but also correct them on the fly.
Some of us who have been around computers longer may remember the old parity memory that used to be on sale at a slight premium over regular memory. ECC and Parity memory share some likeness in that both can detect errors in the memory, however, ECC takes it one step further by correcting the error and preventing it from affecting your application.
As I mentioned, ECC is something only a server or mission critical system would need (sort of like Registered Memory) because memory errors are very rare and because the number of errors likely to be experienced by a system is proportional with the amount of RAM on that system - since servers tend to have a few Gigabytes of memory, and because they are on 24hours a day and also deal with huge amounts of pretty important data, it's not hard to figure out why ECC is considered a must for any serious server application.
ECC Slows down Boot time too. Another reason why you wouldn't want ECC in a regular system is because once ECC checking is enabled you better be prepared for the longest RAM check you've ever seen in your life. It is literally several times slower than regular memory checking during POST.
Also of note, because of the way ECC works, you can expect it to perform roughly 2% slower than non-ECC memory.
Heres some information I provided in another PAQ: ( https://www.experts-exchange.com/questions/20799798/Difference-between-DDR-and-RD-RAM-and-recommendation-for-new-system.html )
A big difference that made RDRAM desirable (once, but not now) was one of bandwidth.
When DDR first came on the market, it was running at a maximum of 2.1GB/s of bandwidth. RDRAM at the time was doing 3.2GB/s.
Now, however, if using Dual-DDR PC3200 you can get a maximum of 6.4GB/s (PC3200 @400MHz, Dual-Channel) which is superior to that of RDRAM's PC1200-Dual 4.8GB/s.
Also of note, DDR RAM is much less expensive than RDRAM.
How The Two Systems Differ and General Summary
This is taken from overclockers.com:
"RDRAM is a narrow, high speed serial connection.
SDRAM/DDR is a wider, lower speed parallel connection. (DDR is simply SDRAM that squeezes out two actions per clock cycle; something RDRAM already does. I'll use the term "SDRAM" when what I'm saying applies to both current SDRAM and DDR, and "DDR" when it applies only to that).
Just about all the major advantages and disadvantages between RDRAM and SDRAM stem from this difference.
These are two much different ways of handling data flow. RDRAM does a little very quickly. SDRAM does much more but more slowly.
The wiring on RDRAM modules is technically more challenging, but there is much less of it. It operates best with simple configurations; performance degrades as you add more devices. This is typical of serial devices. "
A big difference that made RDRAM desirable (once, but not now) was one of bandwidth.
When DDR first came on the market, it was running at a maximum of 2.1GB/s of bandwidth. RDRAM at the time was doing 3.2GB/s.
Now, however, if using Dual-DDR PC3200 you can get a maximum of 6.4GB/s (PC3200 @400MHz, Dual-Channel) which is superior to that of RDRAM's PC1200-Dual 4.8GB/s.
Also of note, DDR RAM is much less expensive than RDRAM.
How The Two Systems Differ and General Summary
This is taken from overclockers.com:
"RDRAM is a narrow, high speed serial connection.
SDRAM/DDR is a wider, lower speed parallel connection. (DDR is simply SDRAM that squeezes out two actions per clock cycle; something RDRAM already does. I'll use the term "SDRAM" when what I'm saying applies to both current SDRAM and DDR, and "DDR" when it applies only to that).
Just about all the major advantages and disadvantages between RDRAM and SDRAM stem from this difference.
These are two much different ways of handling data flow. RDRAM does a little very quickly. SDRAM does much more but more slowly.
The wiring on RDRAM modules is technically more challenging, but there is much less of it. It operates best with simple configurations; performance degrades as you add more devices. This is typical of serial devices. "
Now, to be specific on the 256Mb module that didn't work in your bosses PIII system: It is likely that the generic 256Mb module you purchased was high-density, and that your bosses sytem required single density pc100 of a certain spec. As I mentioned, a good place to find exactly what was required is on www.crucial.com
Did you need any more information? If you have more questions, please let me know and I'll be happy to help out.
AlbertaBeef
Did you need any more information? If you have more questions, please let me know and I'll be happy to help out.
AlbertaBeef
MrSkinny: Re: your comments:
>>Thats quite difficult to answer, there are many variations. For instance, an early Pentium 3 Motherboard may only
>>support upto pc-100 as pc-133 was not around yet. A later board capable of supporting 133 will also support slower
>>speeds like 100 and 66. As a rule I would say P3/Athlon will use either PC100 or 133 depending on how old it is,
>>P4/AthlonXP generally support DDR only but some boards can also take PC-100/133.
As mentioned, it's not necessarily the jedec specification (that's what the PC66/100/133 is, a jedec spec.), but often there is density, speed and chip configuration requirements. And although some boards that supported 133 could support 100 and 66MHz ram, there were times that they wouldn't.
Also of note, if the cpu is 100MHz, you can't use 66Mhz ram. The memory bus speed must match the cpu bus speed.
Initial P4's used RDRAM from rambus. The first P4's to use non-rambus memory actually used SDRAM (performance was pitiful, though) and later P4's started being offered with DDR. It wasn't the cpu though, but the chipset and design of the motherboard that determines what kind of RAM it takes. The cpu has nothing to do with it, really.
Athlon XP's were at release able to use SDRAM and DDR, depending on the board, and many boards offered support for both (but not at the same time).
Now, you'd be hard-pressed to find a new system being sold with SDRAM, or RDRAM. Almost everything whether intel or AMD comes with DDR. PC3200 is currently the fastest ram in the jedec specification (at 400MHz), but currently many manufacturers also offer ram in 433MHz (PC3500), 466MHz (PC3700), 500MHz (PC4000) although jedec has yet to make any PC3500, PC3700 or PC4000 specs, so it should not officially be called such.
>>Thats quite difficult to answer, there are many variations. For instance, an early Pentium 3 Motherboard may only
>>support upto pc-100 as pc-133 was not around yet. A later board capable of supporting 133 will also support slower
>>speeds like 100 and 66. As a rule I would say P3/Athlon will use either PC100 or 133 depending on how old it is,
>>P4/AthlonXP generally support DDR only but some boards can also take PC-100/133.
As mentioned, it's not necessarily the jedec specification (that's what the PC66/100/133 is, a jedec spec.), but often there is density, speed and chip configuration requirements. And although some boards that supported 133 could support 100 and 66MHz ram, there were times that they wouldn't.
Also of note, if the cpu is 100MHz, you can't use 66Mhz ram. The memory bus speed must match the cpu bus speed.
Initial P4's used RDRAM from rambus. The first P4's to use non-rambus memory actually used SDRAM (performance was pitiful, though) and later P4's started being offered with DDR. It wasn't the cpu though, but the chipset and design of the motherboard that determines what kind of RAM it takes. The cpu has nothing to do with it, really.
Athlon XP's were at release able to use SDRAM and DDR, depending on the board, and many boards offered support for both (but not at the same time).
Now, you'd be hard-pressed to find a new system being sold with SDRAM, or RDRAM. Almost everything whether intel or AMD comes with DDR. PC3200 is currently the fastest ram in the jedec specification (at 400MHz), but currently many manufacturers also offer ram in 433MHz (PC3500), 466MHz (PC3700), 500MHz (PC4000) although jedec has yet to make any PC3500, PC3700 or PC4000 specs, so it should not officially be called such.
Alberta,
Whilst I am aware of all that, I did not have the time to write three or four pages on it! :-)
Regards,
Skinny
lol. I type faster than most. I've played piano for 30 years and credit that to my typing speed of >120wpm.
Once at work while working on a manual for software I developed, I realized a bunch of people were standing behind me watching . . . so I turned around to ask what the wanted and one of them said "We just want to see how long it takes before smoke comes out of the keyboard..."
Lol. So it's not that I really have that much time... It's mostly that I type really fast.
Once at work while working on a manual for software I developed, I realized a bunch of people were standing behind me watching . . . so I turned around to ask what the wanted and one of them said "We just want to see how long it takes before smoke comes out of the keyboard..."
Lol. So it's not that I really have that much time... It's mostly that I type really fast.
Impressive! :-)
Morpheus30 - Did you need more information? If so, please ask in detail. If not, please accept the answer that provided the information you required, or split points among experts if appropriate.
Thank you,
AlbertaBeef
EE Page Editor, Microchips/Desktops TA's
Thank you,
AlbertaBeef
EE Page Editor, Microchips/Desktops TA's
ASKER
Sorry it took me so long to get back, but my Internet connection at home was down until Sunday. I'm increasing the points and splitting them...