IBM 300GL

[Retro6]

I have an IBM 300GL its the 200MHz version...

Does anybody know anything about this computer?

I'm having problems trying to get this computer to read a whole memory stick. The computer can take a maximum of 128MB of SD RAM PC 133 and has Two RAM slots each can take a maximum of 64MB.

So the computer will not read all of my RAM it will only read 15MB out of 64MB and that is it... the RAM is not faulty and has been tested I have tried many different RAM sticks but get the same results. I've done everything I can to clean the RAM slots with compressed air etc etc, all the pins look good there are none out of place and all the electrolytic capacitors look good on the motherboard, no bulges or leaks there all clean however that doesn't mean that there aren't any faulty capacitors.

First thing I need to rule out is whether this computer took IBM specific RAM? I know from experience that some old computers would require specific RAM this is what I need to rule out.

There were a few versions of IBM 300GL computers mine is the one with the 200MHz processor installed from around 1997.

Could anybody please help I'd really like to get this rare computer back in working order for MS-DOS and Windows 95.

If anybody has any knowledge of this IBM computer I'd be very grateful.

Thanks.

 

[Retro6]

It has onboard graphics, the graphics chip is a Cirrus CL-GD5446 I don't have a compatible video card for this computer.

I did install a new CMOS battery but there always remains a configuration error on the BIOS and only see's 15MB of RAM. I did read somewhere that the computer may only take double sided memory so I've ordered another stick of RAM double sided this time to see if it works so if that doesn't work I'll try to track down some PC66 RAM to see if that does the trick.

It would make sense it only taking PC66 RAM seeing that SD RAM was pretty new at the time in 1997.

 

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So I've been doing a bit more research and it would appear my theory was correct that the RAM I was using was incompatible I was using PC133 PC100 RAM So I'm going to order some PC66 RAM and cross my fingers that its the solution to the problem.

 

[Retro6]

The RAM 32MB PC66 arrived today but its double sided... it looked single sided on the picture when I ordered it but I installed it anyway to the computer and it saw all of 32MB I thought great so I put the rest of the computer back together fired it up and got a continuous long beep no post... so I opened up the computer again unplugged stuff from the motherboard like drives and and stuff then tested again and I still got the long continuous beep and no post so I thought the RAM has just died so I took it out then tried it again and it worked so I then plug the rest of hardware back in to the motherboard, Hard Drive, Floppy, CD ROM tested it again to make sure and it posted ok so I installed MS-DOS then when the computer restarted it would not post so I switched it off and back on again and got that long continuous beep again no post...

I've decided to unplug everything from the board and I took the board out of the computer to check underneath to make sure there are no hairline cracks or breaks in any of the tracks on the motherboard... all looks good. So I put it all back together again and test it one more time and it boots with no problems I switch it off and back on again and that long continuous beep is back with no post.

Edit: I've just got it going again after a short break from it, first thing I noticed is that the processor is showing as 120MHz where as before it showed as 200MHz so it could be that the dip switches on the motherboard need a good clean with some electrical cleaner that could also be contributing to the problem...

There is a possibility that the voltages on the power supply could be dropping off which is common for old power supplies and easily repaired...

 

[Retro6]

Standard thing in something so old, check for the usual signs of corrosion around batteries and any build up of fluff around capacitors - especially if the metal on the top is domed or split then clean and/or replace as necessary.

Its all pretty clean inside with no corrosion and has a new CMOS battery, all the capacitors are also clean, no bulges or leaks. I'm sure the problem now lays with the PSU. I have a suitable ATX power supply for it that has the AT connector to power the PCI board but I will need an ATX to AT cable adapter for the motherboard, I can get one from China dirt cheap and I'll probably have to wait about a month for it to arrive. In the mean time I'm going to test the voltages on the old PSU and there are likely bad caps inside the PSU so providing that is the problem and I can get the correct electrolytic capacitor replacement values then I'll be able to restore the original PSU.

It does seem like the PSU is dropping out but when it does work the computer function's as it should.

 

[Retro6]

I might just have to cut my losses with this IBM.

The computer is now powering up ok and booting I go to install Windows 95 only to get an error message saying that I only have 502784 bytes of RAM and Windows 95 requires 3000000 bytes. The computer has 32MB of RAM and shows 32MB of RAM in the BIOS and counts 32MB RAM on start up so its either a crappy disk I got sold or there is yet another RAM problem.

I don't get it because I managed to install Windows 98 SE with no problems but I want Windows 95 on this computer.

 

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I just had another look in the BIOS and something is corrupted in memory resources so I need to change something in the settings but what I do not know. There is always a configuration error in the BIOS.

 

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Well tried it the second time and windows 95 installed and I got video drivers and audio straight away... I went and changed it to true 24 bit color but now the display on the monitor is not supported Do I have to wipe the hard drive and start again or is there any way of getting back into Windows? I don't have a CRT display I only have LCD monitors.

I don't have the option of safe mode.

Edit: I managed to get into safe mode and change the display settings, I don't know why it wasn't working the first time.

I love the look of Windows 95 although there is still some work to do to get the computer to operate normally I'm quiet chuffed that I got Windows 95 on it...

I think the next thing to do at some point is to recap the power supply and motherboard to eliminate problems although all the caps look ok it dosen't mean that they are ok and could be out of spec causing the motherboard to behave erratically. Sometimes the computer works and sometimes it doesn't.

 

[Retro6]

Its needs something because it is very unstable. I tried installing office 97 and that failed. Its taken an hour so far to install Publisher 97.

The computer dosn't always turn on, sometimes it will just have a long continuous beep and switching it off and back on again it will power up normally so not the most reliable computer. The RAM has been tested as well. So if the caps are all good that just leaves the power supply.

Its been 1 hour now and its only at 67% installing Publisher. I've had enough of it for today.

I don't know why people pay so much money for these old computers. I only paid 20 quid for it back in 2015 good job really.

I'd never pay the prices people want for these old machines considering... and you just never know what problems they will have. Its like buying an old car it may run but you just don't know what gremlins it will have.

 

[Retro6]

300GL prices are going up? It's just a business PC, nothing special.

It shouldn't be that slow I remember installing office 2000 on 486 PC's at 66 MHz years ago when I worked for a computer recycling place and they were quicker than this one I have. Oh boy I wish I had kept the 486 computers I used to have, I had about 15 of them because the place where I used to work no longer wanted 486 computers so people took them home that was back in 2003/4 when they were worthless and seen as junk but now each one would be worth 200 to 300 pounds and they were excellent reliable computers.

I will do everything I can to sort out the IBM 300GL and if I get no luck I will sell it on as it is or keep it and in the next 5 or 10 years it might be worth a lot more. I have ordered some more RAM. Just encase... the RAM was only 2 pounds each PC66 32MB and I bought the last lot of 2 sticks so I'll have 64MB in total. Its probably worth having spare old RAM anyway.

 

[Retro6]

After looking at the errors I've been getting and the way the computer behaves all points to the RAM such as the computer suddenly slowing down Error messages such as "This software requires 4MB RAM or more" when clearly the computer has 32MB RAM and shows 32MB RAM in BIOS and in system information in Windows, it would also explain why the computer doesn't always power up first time and will give a continuous long beep indicating a RAM problem...

So maybe the SD PC66 RAM that I'm using is still perhaps a bit to modern for the machine. The RAM stick is good and has been tested. I was having a look on ebay and I noticed that there is some even older looking SD EDO RAM...

I've taken a few screen shots of some examples, so the first is the more modern SD PC66 RAM



This is the older SD EDO RAM which could be my answer to getting the this computer working correctly

 

[Retro6]

That chipset will use either EDO or SDRAM.

To be honest I'd stop plowing money into it, if the PSU or board appear to be problematic.

I don't spend much on RAM just a couple quid here and there.

I may have had a breakthrough with this... so my IBM 300GL has the model number 670 and I've looked it up and that IBM 300GL Model used server memory.

 

[Retro6]

I've put the computer away for now and I'll be getting some server EDO RAM to try on it and if the problem remains I will try another power supply I can modify a standard ATX PSU by cutting and soldering the leads from the old PSU on to the ATX PSU all the voltages are the same. If the problem still remains then I'll junk the motherboard and I'll put the rest in the attic for a future project.

There's really no point in selling it because its very heavy and would cost quiet a bit to post and generally nobody would be interested in an old IBM that they will have to collect. There are a few old computers on ebay on collection only and nobody bothers to bid.

I got lucky... I won a nice Pentium PRO 133MHz PC for 35 pounds... well I say lucky now but I don't know if it works so it be a surprise and if the worse happens and it turns out to be another junk box then I have a fully working P4 motherboard to put inside it that's Windows 98 compatible so I'd be able to build a Windows 98SE gaming machine and the case looks ATX compatible.

 

[Retro6]

Oh well the seller never sent the Pentium PRO computer after all and I ended up getting a full refund. I expect the seller never sent it because he wanted more money for it. I'm not having much luck at all lately.

Back to the IBM 300 GL I've ordered the EDO RAM which is worth a try at least then I will know for sure if EDO RAM solves the RAM error problems as PC66 RAM may still be to modern for this old machine. If it works its happy days if not then it will get a complete revamp with another motherboard and PSU.

I have done the measurements of the back as I will need to cut away some metal so it can take a standard ATX mother board. There isn't much to cut away and then I'll be 3D cutting some perspex to cover up any ugly gaps around the I/O shield and I'll cut out 2 slots so I can fit a low profile video card and low profile sound card. Providing that I get no joy with the EDO RAM I'll be doing this mod. I already have a spare ATX P4 motherboard and PSU and then it will get a Windows 98SE install I'll also upload pictures on here once its done.

One thing I just realized is that the processor cooler on the P4 board sits a little high so there isn't much clearance between top of the IBM case so I'll need to cut and make a vent on the top of the case for better ventilation for the processor.

 

[Retro6]

So I'm still waiting for the EDO RAM to arrive which should arrive next week.

I have been doing a lot of thinking... before I do a revamp on this machine, I'm going to look at the fault in more detail providing the RAM doesn't sort the problem out.

So the fault at the moment still remains with the RAM error and the computer not always turning on first time with continuous beeping, I have to switch it off and back on again and normally after the second or third try it turns on with no beeping and runs as it should... this could indicate a PSU problem or a lose connection somewhere, the fault also could be a faulty capacitor in the PSU in which voltages maybe dropping on one of the voltage outputs of the PSU. It could also be that some of the resisters in the PSU have gone out of spec.

Now I have a few options if it is the PSU.

Option 1 diagnose and repair the PSU (if there are failing components) then its more likely to be a bad capacitor or two or some bad resisters. It wouldn't be anything else in this case as the PSU would not work at all such as transistors or diodes shorting out and in those cases the PSU fuse would blow or the PSU would go bang. A PSU can still work with bad resistors or failing capacitors but may not output clean voltages.

Option 2 (providing the PSU is the suspect) I have lots of working ATX power supplies I'm sure I could sacrifice one for capacitors to put in the IBM PSU providing that they are of the same value or close enough and I have bags of resistors.

Option 3 as said before I could just cut the connectors of an ATX PSU and solder on the connectors from the IBM PSU if they put out the same voltages 12v 5v 3v so that be straight forward.

If its not a PSU issue. Then it will be back to the systemboard. So what I will do is remove the system board and begin some trouble shooting. I will check all connections and joints and check things for continuity. I'll also check for any dry joints on the system board.

So I think I've covered everything there.

If I still can't solve the problem then the revamp will start.

The first stage now is to wait for the RAM.

 

[Retro6]

I've made progress and I've found the problem. The PSU is the culprit and the motherboard is in good working order.

So Now I just need to sort out the power supply and it should be good to go.

 

[Retro6]

If you want to test it with a modern power supply you could get one of these (ebay). I've used one on my 386 PC and it's worked fine for months.

I've got quite a few ATX power supplies knocking about I've selected a 300Watt HEC-300AR-PT and I already have that ATX to AT adapter. I will just need to cut and solder the 5volt 3 pin connector from the old power supply to the new power supply.

 

[Retro6]

I've almost finished the new modded ATX PSU I managed to find a circuit diagram of the old PSU and work out what everything does so that when I plug the new modded PSU in to the motherboard I don't go blowing anything up on the motherboard.

It wasn't as straight forward as I first thought... there were also many connections rather than just two standard AT connectors the IBM uses four AT connectors, Two for the motherboard one to power the processor and the other is to power the PCI/ISA slots then there were two more connectors that are three pin plugs.

I've done most of it now so I've just got two more connectors to solder and that is pretty much it. I have all the correct color heat shrink for the wires as well

I decided not to use the ATX to AT adapter as the wiring is different for the IBM 300 series boards and I could burn something out on the board, if something ran on 3 volts or 5 volts and got 12 volts something will go up in smoke and that would be the end of that.

This is the wiring diagram I've been following for the AT P connectors.

 

[Retro6]

Update... I finished the power supply conversion I plugged it in to the motherboard and I was expecting something to go up in smoke but all is working well now I've just got a configuration error to sort out in the BIOS.

Next I've just got to trim a tiny piece of metal of the back of the case so that the new PSU can screw in, and then connect up all the drives. I don't have that RAM issue anymore neither.

Could anybody help me with this error I get in the BIOS? The error is nothing new its always been there but I can't seem to get rid of it its always there on start up I tried setting the BIOS to default settings but its like the BIOS is not saving settings... it has a new CMOS battery the only thing I can think of at this point in time is that the contacts of the CMOS battery socket isn't making good continuity with the battery which would be wishful thinking as that would be easy to repair...

Anyway I was just wondering if somebody could help me with this error.

 

[Retro6]

I've sorted all the problems out now. I've now got the IBM 300GL working correctly