can anybody tell me, I know that DIMM memory modules come as SDRAM, DDRRAM or RDRAM - I'm guessing SIMM modules are generally too old to come like this? so when you get a SIMM module, is it SDRAM or ? I probably haven't explained this very well, but hopefully somebody knows that I'm on aobut!
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SIMM modules
- Thread starter y2k1981
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- Thread starter
- #3
SIMM modules generally came in pairs. That is how they came for my IBM Aptiva P133. The best way to buy them is to cannibalize them from older computers that are ready for the junkpile. There might be some sites on the internet that sell old computer parts.
Here is a site that sells used memory I found just by searching in 5 minutes:
SIMMS had an access time of 70ns compared to 5-7ns of todays memory. Most common were 72 pin simms sold in pairs. Around that time many computer manufacturers also had memory modules that were proprietary and only fit and worked in their motherboards. If you do not like my post feel free to point out your opinion or my errors.
Here is a site that sells used memory I found just by searching in 5 minutes:
SIMMS had an access time of 70ns compared to 5-7ns of todays memory. Most common were 72 pin simms sold in pairs. Around that time many computer manufacturers also had memory modules that were proprietary and only fit and worked in their motherboards. If you do not like my post feel free to point out your opinion or my errors.
thatrenowned
MIS
Take a look at
This site gives loads of other terms as well...can be useful at times.
Regards
This site gives loads of other terms as well...can be useful at times.
Regards
This is the cheapest place I've found for new EDO 72 pin SIMMs:
(In USA) "A little knowledge is a dangerous thing....."![[idea]](/data/assets/smilies/idea.gif "[idea] [idea]")
(In USA) "A little knowledge is a dangerous thing....."
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- #8
thanks all for your responses and for the URL's. Is it still possible to get 30 pin simm's or will I have to remove the 72 pin simm's I have and replace them with higher capactiy 72 pin ones? Also, what's parity and non-parity all about? I came across it on another site while searching for simms. memoryx.net
dentarthurdent
Technical User
30 -pin Simms are very difficult to get nowadays. I assume you are asking this because your computer supports both 72 and 30 pin simms. Even if you could get 30-pin simms it would be a bad idea as most of them were only made in 1mb size and most motherboards don't support the mixing of 30 and 72 pin modules. The golden rules for 72 pin simms are:
Install in matched pairs.
All memory should be of the same type.
As regards parity, most early PC's which used 72 pin simms came with parity memory. This is just an old technique for error checking. It used a extra bit in the data stream to verify data. But parity memory was expensive to produce and companies started to produce reliable memory that could do without it, non-parity. Eventually it became virtually impossible to find parity memory but no-one really cared.
FPM 72-pin simms (or 70ns memory to give it's access time) were then replaced by faster EDO memory (enhanced data output or 60ns memory). Again virtually all this memory was non-parity.
Parity and non-parity memory should not be mixed.
EDO and fpm memory can be mixed but this often has odd results, the board will run at the speed of the slowest memory.
When sdram (or 168pin) came out it was much faster than anything else (access time of 8ns) and was much easier and more forgiving to install so we all dumped the old memory and bought the new stuff...but thats another story.
If you have specific queries about board compatibility I will try to help.
Will.
Install in matched pairs.
All memory should be of the same type.
As regards parity, most early PC's which used 72 pin simms came with parity memory. This is just an old technique for error checking. It used a extra bit in the data stream to verify data. But parity memory was expensive to produce and companies started to produce reliable memory that could do without it, non-parity. Eventually it became virtually impossible to find parity memory but no-one really cared.
FPM 72-pin simms (or 70ns memory to give it's access time) were then replaced by faster EDO memory (enhanced data output or 60ns memory). Again virtually all this memory was non-parity.
Parity and non-parity memory should not be mixed.
EDO and fpm memory can be mixed but this often has odd results, the board will run at the speed of the slowest memory.
When sdram (or 168pin) came out it was much faster than anything else (access time of 8ns) and was much easier and more forgiving to install so we all dumped the old memory and bought the new stuff...but thats another story.
If you have specific queries about board compatibility I will try to help.
Will.
All SIMMs are obsolete.
About 30-pin & 72-pin... These are not interchangeable.
If old motherboard supports 30-pin SIMMs and 72-pin SIMMs at the same time (i.e. mobo have 30-pin and 72-pin cradles) it's possible to use them together but not any old motherboard supports this.
30-pin SIMMs and 72-pin SIMMs may support or not support parity checking.
About 30-pin & 72-pin... These are not interchangeable.
If old motherboard supports 30-pin SIMMs and 72-pin SIMMs at the same time (i.e. mobo have 30-pin and 72-pin cradles) it's possible to use them together but not any old motherboard supports this.
30-pin SIMMs and 72-pin SIMMs may support or not support parity checking.
Some motherboards allow 30 with 72 if you plugged the 72 in the second 72 slot, but if both 72 are used no 30.
486s generally didn't require paired memory, the DIMM was standalone. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
486s generally didn't require paired memory, the DIMM was standalone. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
- Thread starter
- #12
Thanks everybody for all your posts, I assumed that when all the slots were there, that you could use them all, provided you ensure that a bank was fully populated or fully unpopulated etc.
I have a 486 with 2 72 pin slots and 4 30 pin slots. I have 16MB RAM, so I'm guessing that each stick is 8MB each. I presume they have to be the same, or it wouldn't work, but they don't "look" the same, one has blocks on both sides, while the other has blocks on just one side. I know that it would be kinda' pointless using the 4 30 pin blocks, seing that the most you could get out of them collectively would be 16MB, but I was hoping to upgrade the 72 pin ones also - guess not. So I'll just have to upgrade the 72 pin ones instead. And if it's EDO, I can assume it's non-parity?
next question, I need to make sure if my motherboard is 133Mhz, that the memory is also 133Mhz, correct? How could I find out if the motherboard is 100 or 133? It's an AT motherboard (obviously!) with 486 processor, I don't know much more than that. Am I correct in saying that 133 RAM will work in a 100 or 133 motherboard, but only at the lower speed if the motherboard is 100Mhz??????
Again, thanks everybody
Martin
I have a 486 with 2 72 pin slots and 4 30 pin slots. I have 16MB RAM, so I'm guessing that each stick is 8MB each. I presume they have to be the same, or it wouldn't work, but they don't "look" the same, one has blocks on both sides, while the other has blocks on just one side. I know that it would be kinda' pointless using the 4 30 pin blocks, seing that the most you could get out of them collectively would be 16MB, but I was hoping to upgrade the 72 pin ones also - guess not. So I'll just have to upgrade the 72 pin ones instead. And if it's EDO, I can assume it's non-parity?
next question, I need to make sure if my motherboard is 133Mhz, that the memory is also 133Mhz, correct? How could I find out if the motherboard is 100 or 133? It's an AT motherboard (obviously!) with 486 processor, I don't know much more than that. Am I correct in saying that 133 RAM will work in a 100 or 133 motherboard, but only at the lower speed if the motherboard is 100Mhz??????
Again, thanks everybody
Martin
Actually should be pc66. And higher speed may or may not work.
Your guess about 8/8 is correct, but not because they are different. The combinations available don't add up to 16 except that way. Choices 256kb, 512kb, 1mb, 2mb, 4mb, 8mb, 16mb, 32mb. The 512, 2mb, 8mb, 32mb generally came with memory mounted on both sides and some motherboards had problems with it.
486s would allow you to mix the strips. But some required the largest to be found first. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
Your guess about 8/8 is correct, but not because they are different. The combinations available don't add up to 16 except that way. Choices 256kb, 512kb, 1mb, 2mb, 4mb, 8mb, 16mb, 32mb. The 512, 2mb, 8mb, 32mb generally came with memory mounted on both sides and some motherboards had problems with it.
486s would allow you to mix the strips. But some required the largest to be found first. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
- Thread starter
- #14
so no matter what SIMMs I get, they'll probably be faster than the motherboard anyway (and so will operate at the speed of the motherboard), correct?
Is there anything else I need to take into consideration? Like the speed of the processor? I know about the banks, and the width of the board etc.
Again, thanks everybody
Is there anything else I need to take into consideration? Like the speed of the processor? I know about the banks, and the width of the board etc.
Again, thanks everybody
May or may not work. I've run across some that wouldn't. Ed Fair
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
unixstuff@juno.com
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
y2k1981 if you have old 486-based motherboard it can't to be 100 or 133 MHz. If you have 486SX33, DX33, DX2-66, DX4-100 CPU, your mobo's bus speed is 33 MHz. Only multiplier is changing (x1, x1, x2, x3 respectively). In a 486DX2-80 case you bus speed is 40 MHz. 486DX50 - 50 MHz. 66, 80, 100 - these are internal CPU frequency. But the memory acts with bus speed, i.e. 33 or 40 MHz. If you have the mobo's manual or jumper settings are written on motherboard's surface you can check the jumper's settings on motherboard and know your mobo's bus frequency.
All 72-pin SIMMs which you today can find, will be compatible with your motherboard, excluding, maybe, these about which spoke edfair. There are no speed limits in old 486-based mobo's for SIMMs.
All 72-pin SIMMs which you today can find, will be compatible with your motherboard, excluding, maybe, these about which spoke edfair. There are no speed limits in old 486-based mobo's for SIMMs.
I just added 64MB (2 32MB EDO 72 pin) to my old 486. They cost $6 each with $7 shipping. The 64MB is only $7 if your mobo can support 64MB sticks.
Buy it here, the cheapest:
"A little knowledge is a dangerous thing....."
Buy it here, the cheapest:
"A little knowledge is a dangerous thing....."
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