PC100 memory - Page 1
Forum section: electronics / repair

author: Bambur
author_rank: Regular Contributor
timestamp: June 19, 2016, 11:28:34 pm
content: Hello to everyone!My old trusty Thinkpad 380Z laptop needs replacing memory. It turns out it is very difficult to find that memory now in my location. It needs EDO 128MB SODIMM 144 pin 3.3V 60ns.On the other hand I can easily find PC100 128MB SODIMM's. It installs nicely, however laptop does not detect it. Does anybody know if it is possible to use PC100 instead of that EDO? I would say EDO is PC66, is it not?There is an 8-pin chip on the memory SODIMM module. Could that be reprogrammed to make it look like EDO?Any input is welcome! Thanks in advance!

author: Monkeh
author_rank: Super Contributor
timestamp: June 19, 2016, 11:36:14 pm
content: EDO DRAM is not SDRAM. They simply are not compatible.

author: CJay
author_rank: Super Contributor
timestamp: June 20, 2016, 08:51:23 am
content: It's entirely possible that the OP is completely unable to afford to replace the laptop and let's be honest, a 380Z is still a workable machine if you have nothing else so comments about the speed, performance etc. aren't helpful unless you're willing to help them replace it.Bambur, no, the memory can't be reprogrammed to become EDO.Which part of the world are you in, I may be able to post some to you if I can find some in my old stock of computer bits?

author: Rasz
author_rank: Super Contributor
timestamp: June 20, 2016, 11:46:04 am
content: obviously this is a part of vintage collectionedo sodimms are available on ebay for ~$30, just buy proper memory

author: Bambur
author_rank: Regular Contributor
timestamp: June 20, 2016, 11:56:14 am
content: Quote from: CJay on June 20, 2016, 08:51:23 amI am in Scandinavia.The thing is that laptop runs some licensed software which works on that particular machine only. Hence, the need to get it up and running again.Is that EDO so special, that PC100/133 does not support the inferface?Could anybody point me to the specs please?

author: Bambur
author_rank: Regular Contributor
timestamp: June 20, 2016, 12:17:05 pm
content: Quote from: Monkeh on June 19, 2016, 11:36:14 pmOh, EDO is not SDRAM. They are not compatible at all then.Now I see. I was hoping it would be possible to get a faster SDRAM working in place of a slower one...

author: grumpydoc
author_rank: Super Contributor
timestamp: June 20, 2016, 12:29:24 pm
content: Quote from: Bambur on June 20, 2016, 12:17:05 pmNo EDO and SDRAM work in a very different way.With EDO RAM each access must be preceeded by an address (in FP mode only the coumn address needs to be provided but basically each transaction includes the address set-up).In SDRAM the CPU fetches a block of data, the base address is loaded and then consecutive accesses are made without providing a new address - a counter in the RAM tracks where the access is going.So you can't put SDRAM into a computer that wants EDO.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 20, 2016, 01:26:18 pm
content: Quote from: blueskull on June 20, 2016, 12:46:19 pmIf its a machine that old (we must be talking 1990's) there might not be a vendor to ask anymoreEven if there were, any PC might need to be running some truely ancient (and awful) version of Windoze which would not be available today (that said I think I have some Windows 95 install media kicking around somewhere andmighteven be able to lay my hands on a set of Windows 3.11 floppies, groan)

author: CJay
author_rank: Super Contributor
timestamp: June 20, 2016, 02:01:33 pm
content: Quote from: grumpydoc on June 20, 2016, 01:26:18 pmIt'll be 95 or possibly 98 on that machine I think. I'd definitely have an image of it, something that old is living on borrowed time.Win3.1 floppies? I *know* I can lay my hands on a set.

author: bingo600
author_rank: Super Contributor
timestamp: June 20, 2016, 03:06:01 pm
content: That's an older ladyhttps://en.wikipedia.org/wiki/IBM_ThinkPad_380http://www.thinkwiki.org/wiki/Category:380ZRamhttp://www.thinkwiki.org/wiki/EDO_60nsI'm afraid i don't have had contact with TP's before 1999 (T600) , so i don't have any of that type of ram laying around.Edit:Seems like you can get 64MB FRU's here : *bay# 171537668131/Bingo

author: macboy
author_rank: Super Contributor
timestamp: June 20, 2016, 03:20:15 pm
content: Quote from: Bambur on June 19, 2016, 11:28:34 pmSDRAM can act as FPM DRAM (Fast Paged Mode DRAM) but cannot act as EDO. Even still, I wouldn't count on SDRAM DIMMs to work in place of FPM DIMMs.Quote from: Bambur on June 20, 2016, 11:56:14 amYes, EDO is that special. It stands for "Extended Data Out" and this is a special addressing mode that previous DRAM (Fast Paged Mode) did not support. SDRAM also does not support EDO addressing schemes. EDO was a short lived and dead end tech.I have had success with cloning the physical PC hard disk into a VMware (or VirtualBox) virtual machine, then booting and running that just as if it was the original real PC. This way you don't need to reinstall Windows or the licensed software, but you get the benefit of your modern CPU speed, display, etc. Most software will not detect any issue (it's still the same Windows installation, same registry, same file system, etc.) and will run happily. Windows from XP and newer may detect the move and give you licensing grief.Quote from: blueskull on June 20, 2016, 03:18:28 pmThis would be fine if the machine needed PC100 or even PC66, but it requires EDO and nothing else.

author: Shock
author_rank: Super Contributor
timestamp: June 20, 2016, 03:27:09 pm
content: From the sounds of it you are making things difficult for yourself. This is probably a $10 part on Ebay in the states.Look on the ram there will be a sticker with the IBM logo with two alpha numeric numbers. One is the P/N or part number and will be consistent among parts of the same spec. The other is a FRU which may change based on a new batch or a different vendor.Hopefully you have confirmed the fault is in fact ram and are running a memory test and can get somewhat consistent failures.. There can be many other problems on the main PCB, poor or dirty contacts in the slot, a bad joint on the ram pcb or other things due to age and heat.Unless it's specific hardware or a dongle on that laptop like the serial interface any admin worth his salt can move that software over to a virtual machine while you chase the part. The other reason for doing this is if it's that important you should get it backed up before you mess with installing ram and corrupting data.

author: Bambur
author_rank: Regular Contributor
timestamp: June 20, 2016, 08:36:48 pm
content: Quote from: macboy on June 20, 2016, 03:20:15 pmThanks a lot for the explanations! It is much clear to me now.It seems EDO is very special indeed and the only way to go for the machine.I have tried many PC100 and PC133 SODIMM's and some other newer ones. The result is always the same. Unless it is EDO (I could find a couple of 16 and 32 MB), machine just does not see it.I had seen that eBay offer before I posted here. It is a pain to get it from the States down here, plus now it seems it is not a true EDO in fact. By the way, how do you know it is a PC133 clone? Do you think it would be worth trying it anyway? Or is it certain it will not be any good?

author: bktemp
author_rank: Super Contributor
timestamp: June 20, 2016, 08:47:22 pm
content: Quote from: blueskull on June 20, 2016, 08:41:57 pm1/60ns=16.67MHzYou can't specify PC66/100/133 for EDO RAMs because they have no clock frequency.

author: Bambur
author_rank: Regular Contributor
timestamp: June 20, 2016, 10:13:29 pm
content: blueskull, thank you for sharing the article!It is 144-pin SODIMM module in my particular case. It is likely 3.3V (I have not measured actually).

author: Shock
author_rank: Super Contributor
timestamp: June 20, 2016, 10:33:06 pm
content: It wasn't all that special at the time nor is it rare. It's just that EDO is from 25 years ago and used the SODIMM form factor.Think of this way:Technology - EDO memoryForm factor - SODIMMPin count - 144Voltage - 3.3Speed - 60nsIf you are upgrading to 128MB using just any old stick rather than the parts that were known to work in it you might as well flip a coin, PC's are very fussy over memory. If you run out of options and ignored what I have said in my last post the next best thing is to go up inspeedvalue to 70ns but you will not get any performance increase and just add more chance of running into problems.

author: helius
author_rank: Super Contributor
timestamp: June 21, 2016, 01:04:10 am
content: Quote from: blueskull on June 20, 2016, 09:28:08 pmNo, it really doesn't. You're still thinking of the device as if it was a SDRAM.The maximum throughput is determined by all of the timing specifications TOGETHER. The 60 ns (which is called the 't_RAS' or RAS access time) is only the first requirement. After that, you must also satisfy all of the other requirements (on a standard commercial part there can be 60 or more specified time periods that the user must obey for correct operation, including separate setup and hold times for each command type. This is the whole meaning of asynchronous). The total back-to-back cycle length is much more than 60 ns; this is the motivation for Fast Page Mode, of which EDO is simply an enhanced version. It elides a part of the cycle to make it go faster, since the row buffer still contains the previously accessed row and doesn't need to open it again.QuoteCompletely inapplicable.QuoteThe article says,QuoteThis means that if an access is 30 ns (1/33.3MHz), and the memory bus is 64 bits wide (two 72-pin SIMMs, typical for Pentium systems), then peak output is 266 MB/s. This is NOT for complete transactions, only for follow-up reads to an already open row. You can see that it has nothing at all to do with the 60 ns RAS time, which only applies to row access. EDO has nothing to do with banks, it is only a protocol tweak to make t_CAS timing able to be shorter without causing bus glitches.

author: bktemp
author_rank: Super Contributor
timestamp: June 21, 2016, 05:31:28 am
content: Dual channeling requires seperate data lines (increasing the memory bus from 64 to 128bit). Dual channeling wasn't used at that time, because the CPUs and chipsets did not support it.But in theory every memory supports ganged dual channel operation. Unganged dual channel is only possible with synchronous memory, but DRAMs use static control signals. They need to be applied all the time while SDRAMs register the control signals only at the clock edge if the chip select signal is active. Therefore it is possible to start a operation for one SDRAM chip while the other one is perfoming a burst read.EDO DRAMs were common around 20 years ago, but 128MB EDO DRAM were quite expensive. I can't remember ever seing one being used in a consumer PC. Most PCs at that time used 16 or 32MB EDO modules until technology switched to SDRAM.

author: Bambur
author_rank: Regular Contributor
timestamp: June 21, 2016, 07:00:17 pm
content: Quote from: Shock on June 20, 2016, 10:33:06 pmAny hints on where to get 70ns EDO from?

author: helius
author_rank: Super Contributor
timestamp: July 03, 2016, 11:53:01 pm
content: 60ns to 70ns is not "going up in speed". 70ns is slower than 60ns and will not work if the memory controller uses fixed timing.It looks like the modules you are looking for are available here:http://www.memoryx.com/pc7-2463.htmlwith regard to some comments made earlier, 1990s computer systems required memory modules to be installed in identical pairs. If you put a 64MB SIMM in slot A0 and a 32MB SIMM in slot A1 it wouldn't even POST. That's why the memory bus was described as 64 bits wide (plus parity) using 72 pin SIMMs. Some higher-end systems required sets of 4 identical modules (128 bits wide). It only depends on the design of the memory controller and CPU bus.Those computers also had a concept of "interleaving", where the width of the bus was kept the same, but transactions were alternately sent to different sets of SIMMs. This required the alternative sets to be identical in speed and capacity, even though they were not accessed together. So to enable 2-way interleaving with a 128-bit wide memory bus, you were required to install 8 identical 72-pin SIMMs.

author: DK6400Brian
author_rank: Newbie
timestamp: July 07, 2016, 01:45:28 pm
content: Quote from: Bambur on June 19, 2016, 11:28:34 pmHello. A fellow Dane, with a still going strong ThinkPad from 1996, is calling.My ThinkPad 365XD originally came equipped with 8MB onboard soldered EDO-RAM and a slot which IBM specified to be used with a 32MB EDO-RAM SO-DIMM module.However, early on it was clear that the slot could take a 64 MB module, bringing the total up to 72 MB.In fact, I got my hands on one of those 128 MB EDO SO-DIMM modules you're wishing for and placed it in the slot, just to find out that the memorycontroller only recoqnized half of the capacity. It was useless because it still shows 72 MB in total.I therefore came up with the bright idea of desolder the four 16mbit onboard memorychips (giving 8MB in total) and replace them with four of the 128mbit chips from the 128 MB memory module. This is a task to be done later.Anyway...just all this bullocks to tell you, that you really need to buy EDO-RAM, 144pin, SO-DIMM, 60ns.According to the servicemanual:https://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles/38zhmm.pdf...your ThinkPad is equipped with 32 MB onboard (almost non-removable) EDO-RAM and a slot to be equipped with a maximum of 64 MB, bringing the machine to a total of 96 MB RAM.If you buy a 128 MB EDO-RAM, 144pin, 60ns, SO-DIMM module and plug it in, you machine will still only recoqnize half of it and you'll still be left with total of 96 MB. It's *NOT* possible to exceed that.You can not lift the memory above that limit, unless you plan to do exactly the same hardware modification as I intend: Desoldering and removing the onboard memory chips (Your ThinkPad 380Z is most probably equipped with four 64mbit EDO-RAM chips) and exchange them with 128mbit chips. This way you can probably bring the machine to work with 128 MB in total, if you also have a 64 MB in the slot.This is just a wild guess and a shot in the dark if this will ever work.So if you're hungry enough, buy a 128 MB module if you can find it and use it, having the machine recoqnizing the 64MB, until I manage to do the hardware modification with success. Then we'll know if it's possible and I might be able to help you by then.Or, find a 64 MB module and use that, if your 380Z is without it.

author: Bambur
author_rank: Regular Contributor
timestamp: August 24, 2016, 01:13:44 pm
content: DK6400Brian, thank you! I just read your post.I ended with buying a 144-pin SO-DIMM 128MB EDO module from the US. I will be getting it in the end of September, when a friend of mine comes back from there and brings it along.I will report back how 380Z Thinkpad sees it.

author: mariush
author_rank: Super Contributor
timestamp: August 24, 2016, 08:14:04 pm
content: The wikipedia page says the 380z supports a maximum of 96 MB EDO sdram. It's a bit weird to see such a number that's not double of something, so my first guess would be that 32 MB is non-removable and the laptop has a slot that could accept up to 64 MB?Anyway, if you decide to buy edo sdram, maybe you shouldn't buy 128 MB edo ram sticks if you're not sure the laptop supports them. They'd probably be very expensive anyway (as they were rare and expensive back then).

author: Bambur
author_rank: Regular Contributor
timestamp: October 27, 2016, 01:48:45 pm
content: As promised, here is the update. I got the memory in my hands finally. It took a bit longer, since it needed to travel a longer way than I thought originally.Anyway, Thinkpad 380Z seems to work fine with 128MB EDO. It sees now 163264KB (128MB on the installed SODIMM and 32MB on the board). Please see the attached photos.Next I will be installing Windows XP