RAM advice

[MarkGreen]

Hi i'm currently trying to setup and upgrade an old PC for a friend. Everything is working now except for the RAM.

The motherboard is an old P1 board and so has 4 SIMM slots and 2 DIMM slots.
I've decided its not worth using the SIMM slots anymore so i went and bought a 256MB PC133 SDRAM DIMM chip. However the computer wont recognise it.
Upon asking around it seems the problem may be I need PC100 RAM because the motherboard is too old to take the PC133.

However I just want to check that this is definatly the problem before I go and buy some more RAM, only to find it doesnt work.

Also, as i'm not too clued up on RAM, does anyone know any online resources that could answer some of my questions such as what is SDRAM? (... I know what it stands for but i'm confused about compatiblity issues between RAM chips and various motherboards)

Thanks for any advice,
Mark

 

[paparazi]

Without the original motherboard manual for reference I would say that each slot probably has a 64mb limit of PC100
Higher density modules are often a problem so are PC133 modules, try and by a couple of second hand 64mb PC100 sticks or mail order, but be warned this older memory type often costs twice the price of newer types. Martin

Replying helps further our knowledge, without comment leaves us wondering.

 

[SESaskDFC]

Howdy:

Based on your details, I doubt if even PC100 will work.. I have an old mobo kicking around like that and it will ONLY work with PC66 dimms..

Don't forget to change the voltage either (there should be a jumper).. SIMM's use 5.5 volt while SDRAM uses 3.3

Murray

 

[r00tMonster]

I had a PII 266 that only worked with PC66 or PC100, PC133 would not boot. I believe the PII 350 was the first to use a 100mhz fsb.

Being a P1, it might want PC66, usually PC100 will work. PC133 might not.

x::0:0::::

 

[PLiNk]

Remember when buying old ram, that some shops now sell EDO ram 16mb for 150$! Reason, old servers that has been running fine for manymany years and that doesn't need to be replaced has ram that goes bust, and the demand is low but steady and the supply has stopped.
A shop I am "working" for sold 2000 chips of EDO ram back to the producer and made 5000$ dollars on the deal.

Honestly, you can invest in RAM just like in stocks!

This only applies in structured markets. You can still get regular, edo and sdram very cheaply if you buy used.

 

[dementg]

I'm not sure if your system will necessarily even support SDRAM. It's possible what you need are EDO DIMMs. In any case, EDO would be the most likely to work. Many systems of that era supported both EDO and SDRAM DIMMs, but I think plain EDO is always supported. I doubt you'd see any difference in performance. An old pentium pro Proliant I use as a home server only works with EDO dimms, SDRAM is unsupported.

 

[drdebit]

You could try a google search for a manual for your motherboard. ( or a look at vendor websites.) If you were able to find one, it might help to identify specifically what memory you should be looking for.

 

[cdogg]

The original Socket 7 motherboards from Intel which supported all Pentium I models 75MHz - 233MHz used EDO RAM. If that's what you have, then SDRAM DIMMS (PC66, PC100, PC133) won't work. You need EDO.

However, it is possible that you have a later model motherboard from a 3rd-party that supports SDRAM. You can only check this if you have the manual (or at least the make/model so we can look it up).




~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[JimInKS]

If you know the MB manufacturer and model try to find it at

http://www.crucial.com.

This will show you suggested memory upgrades.

If you end up using some older simms try

http://www.dalco.com.

They seem to have pretty good prices on them right now. I bought a set (32M EDO $15 ea) and it seems to be working ok.

 

[Comtech]

A motherboard of that vintage also needs SDRAM in matched pairs to work. A single stick won't do it.

Cheers,
Jim

http://members.cnx.net/reboot/

 

[cdogg]

Just for clarification, EDO and SDRAM are separate DRAM technologies and don't work together. Your Pentium I system will use one or the other. EDO DIMMS must be installed in pairs, while SDRAM does not.

~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[Comtech]

Not necessarily.
I have seen boards that take either EDO/Fastpage or SDRAM (168 pin), but not both (because of voltage issues).
In all cases, the SDRAM must be installed in matching pairs as well.

Cheers,
Jim

http://members.cnx.net/reboot/

 

[cdogg]

Comtech,

"I have seen boards that take either EDO/Fastpage or SDRAM (168 pin), but not both (because of voltage issues)"

I don't think we are in disagreement here.

"In all cases, the SDRAM must be installed in matching pairs as well"

Well, take PC66, PC100, or PC133 SDRAM for example. Do they have to be installed in pairs? That would negate the "ALL CASES" statement. Furthermore, I would be interested in seeing just ONE case where 168-pin SDRAM has to be installed in pairs. Not saying your wrong, but I'm curious now...





~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[Comtech]

Unknown vintage/mfg (Intel chipset) Pentium 166 board. 2 SDRAM slots, 4 EDO (72 pin) slots. Tried every permutation of SDRAM. Finally found two matching 64 meg PC100 sticks. Won't work with one, or the other, in either slot. Works great with both in.
Unknown vintage/mfg (VIA chipset) Pentium 233 (non MMX). Same config, but only 2 of each. Found a matched pair of PC66 32 meg sticks, works.
Unknown vintage PC Chips board, same as above. (Board died when the PSU went out and took the video and RAM with it BTW).
I have more examples.
In every case, that I have seen anyhow, the SDRAM must be matched pairs to work, all in boards that have the option of either 72 pin or 168 pin.

Cheers,
Jim

http://members.cnx.net/reboot/

 

[cdogg]

OK Jim! You've convinced me! My understanding before was that the SDRAM spec does NOT require installation in pairs.

However, there appear to be exceptions in certain motherboards like the ones you've listed above. In those cases, it seems that limitations of EDO (each bank of 2 slots must be filled) has been translated to the SDRAM DIMM slots (which is obviously a problem with the chipset, not the memory itself). On other motherboards, those same 168-pin SDRAM modules would work without a partner.

Cool, thanks for straightening that out...


~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[Comtech]

Exactly, it's not a fault of the SDRAM, it's the way the chipset reads the installed RAM. It's like the SD is piggybacked onto the EDO slots. EDO is seriously dense RAM, and most SD is not. This may not even be a chipset issue, but simply the way the motherboard was designed, as if adding the SDRAM slots was an afterthought (replacing two EDO slots), but using the same addressing technique.
When the first "SD only" motherboards came out, this issue no longer arose, because the addressing/architechture/chipset revision had allowed for single sticks.

Cheers,
Jim

http://members.cnx.net/reboot/

 

[MarkGreen]

I didnt realise there was so much that can go wrong when installing RAM! thanks for all the help anyway, I think it will be best to leave the RAM as it is for now and upgrade the motherboard at some point!!

 

[dementg]

30-pin SIMMs are 8-bit
72-pin SIMMs are 32-bit
168-pin DIMMs are 64-bit

Though chipsets sometimes make exceptions, I think this is the general rule:

Most 386s and all 486s had a 32-bit memory bus, and therefore only needed 1 72-pin SIMM to work. I had a 486 that let me boot with only 2 30-pin SIMMs, but that was just the chipset being nice. Starting from the pentium, they used a 64-bit memory bus, so that's why you had to start using pairs of 72-pin SIMMs (to fill the 64-bit bus).

I don't think FPM/EDO/SDR/DDR/whatever makes any difference to the issue. The boards I've dealt with have only needed 1 DIMM per bank, including 3 EDO based systems (2xi430VX and i440FX chipsets) and a couple P2/K6 (i440GX, VIA MVP3) systems that use SDRAM. I'm at a loss to explain why Comtech has had to use pairs. I don't think that's normally necessary with DIMMs, but I guess it can't always be taken for granted either.