EEVblog #639 - IBM L40SX Retro Laptop Teardown

[EEVblog]

Teardown Tuesday
What's inside a 1991 vintage IBM PS/2 L40SX 80386SX laptop?

Datasheets:
IIT 3C87 Co-Processor: http://datasheets.chipdb.org/IIT/IIT3c87.pdf
WD76C30 http://pdf.datasheetcatalog.com/datasheets2/29/2916422_1.pdf
WD76C20: http://www.datasheet-pdf.com/datasheetdownload.php?id=370726
WD76C10: http://www.datasheetarchive.com/dlmain/Datasheets-8/DSA-153427.pdf
LT1270: http://cds.linear.com/docs/en/datasheet/lt1270afc.pdf
8042 PS/2 Controller: http://wiki.osdev.org/%228042%22_PS/2_Controller
Intel 8 Macrocell PLD: http://www.alldatasheet.com/datasheet-pdf/pdf/160485/INTEL/85C224-80.html

[Ketturi]

I love those old luggable "laptops" <3. Amazing that it works too! All that era laptops that I have owned have had broken hard drives. I myself prefer those with yellow/blue LCD:s, as I remember they had bit better contrast and looked warm and fuzzy.
I remember using Toshiba one to write stories and poems as a kid and I have similar computer as back then which I still use for hackery things like a rs232 terminal or some hardware interfacing for older stuff.

It was not in that good condition however and needed a lot of maintenance and love. All caps were leaky and gone and caused weird problems like the display going grazy and stuff. Also the HDD was broken but I replaced it with a compact flash adapter and 512MB CF card (bios could not even recognize so large card, as it wanted 20 or 40MB HDD, but I managed to get the cf card working with the Seagate disk manager and ontrack bootloader/driver). The floppy drive had broken belt and original battery and power adapter were gone and bunch of more stuff, but I managed to fix all those in some hackish way, and now it is usable again.

I have one idea to put small ARM board in place of old telephone modem, and use the rs232 connection to "call" it. Then I could use machine on the go and have remote network connection to my "mainframe" and do all modern stuff like hang in irc or use internet trough text console browser like lynx  . That would sure get some looks in some LAN party or some other nerd events .

Some pictures and stuff from this Toshiba T2000SX computer: https://www.dropbox.com/sh/e4zjan3bka8hhe4/AABlGGB4IAqpYFJ2VNbMfmlSa

[nitro2k01]

No look inside the PSU? Assuming is not welded shut, that is.

[rfmerrill]

It's not entirely unheard of to overbuild for a prototype build and end up shipping some of it to customers--especially if a sudden part shortage means you can't build any production units!

[digital]

Thank's Dave a beautiful machine with the usual IBM quality,It would have been running the IBM version of pcdos. a look at machines that were built with reliability in mind.Cheers

[ryanmoore]

The hard drive possibly still works (those old drives are pretty tough), it's just that the dead backup battery means the BIOS settings for it have been lost. Old computers like this didn't auto-detect the hard drive so you had to enter the cylinders/heads/sectors parameters from the drive label yourself using the setup floppy - no built-in BIOS menu!

I don't know if you'd get it to work with an SSD. 386/486-era computers usually had a drive size limit of somewhere around 520MB for various technical reasons. You could probably get a 512MB compact flash card working using a CF-IDE adaptor though.

[EEVblog]

You could probably get a 512MB compact flash card working using a CF-IDE adaptor though.

Yes, CF card is probably the go in something like this.

[GK]

Hmmm....nineties laptops... Yuck. Don't miss those 2 degree viewing angle, low contrast screens at all. All I can remember doing on these things back in school is Logo/turtle graphics. That was exciting, not. The screen update rate was so slow the turtle had tails.

[tchicago]

Hi, David
You are right about the older keyboards - they are so much better for typing than the regular mushy membrane types.
The mechanical keyboards are still being made and have a lot of fans, mostly in the gamer community where the precise feel of the keypress is important. The modern mechanical keyboard community has a special terminology for the key types - it uses "color" to describe the way the key feels and sounds.
Here is as short guide: http://www.keyboardco.com/blog/index.php/2012/12/an-introduction-to-cherry-mx-mechanical-switches/ (I've seen more comprehensive one somewhere else, but can't find it anymore)
So if you are interested in buying the mechanical keyboard, the "color" of the switch is the parameter that you should seek. Various manufacturers use the different names for the product, but the "color" of the switch should be either in the product name or in the specs. The "brown key" or "brown switch" is regarded as best for typing. The mechanical keyboards are a bit pricey - $60-120, but usually there are sales, rebates and discounts to look for. This type of keyboards is made to withstand the gamer abuse, so they are pretty reliable.

[rsjsouza]

Adding to tchicago's reply, if you would like to get a buckling spring keyboard, check Unicomp. I bought one two years ago and did not have elbow pains anymore. I will never go back to a cheap keyboard. 

[128er]

Thumbs up for old keyboards (and the teardown too). I love the old clacking IBM or Cherry keyboards. They have a very nice key response.

Here is a picture of a vintage "laptop" that I own. It's a Siemens PG 685. Was used to programm industrial PLC's from the Simatic S5 series. Weighs ~18 kg. Has CP/M-86 and DOS.

[free_electron]

YES ! that's what i call a real computer. Boots straight into Basic ! screw operating systems and their crummy 'c' language.

[SpidersWeb]

YES ! that's what i call a real computer. Boots straight into Basic ! screw operating systems and their crummy 'c' language.

lol yeah, IBM had a contract with Microsoft, so they kept putting Cassette BASIC in their machines right in to the early 90's. So if they fail to boot they jump to it. It's not very useful though - no cassette port = no saving/loading files.

[photon]

IIT, founded in 1987 by one of Weitek's co-founders, later changed their name to 8x8 and their product line to VoIP. They are still in business.
http://en.wikipedia.org/wiki/8x8

[mxmarek]

How about the neat lcd indicators ?

[mattinx]

Love the old computer teardowns

That HDD was definitely spinning up, might be worth a poke to see if the system actually sees it - assuming you can fish out suitable boot disk.

I wish I'd kept my first laptop - 8086 with 640k, two 720k FDDs and a monochrome reflective LCD CGA display (yes, mono, not greyscale - it had to dither for cyan and magenta). Great for working outside in the sunshine, useless for working indoors in low light. It was powered by a tube of sub-C NiCd cells, and I remember having to build a PSU for it because I picked it up at an auction for next to nothing and it didn't have one. It had a bit of a design flaw in that the floppy drives weren't screwed in place - they just sat in molded cutouts in the case, one on either side with a PCB in the centre that both drives plugged directly into. This meant that over time, the drives would work loose and stop functioning - the simple fix being to put a disk in both and press them both in toward the centre of the machine. Ahh - happy days

[RupertGo]

What strikes me about that laptop is how over-complicated it is. A (huge!) external switch mode power supply and tons of linear regulators on a fat heatsink? That odd (and doubtless costly) PLL board? All that 74 series logic glue? I know that state-of-the-art early 90s PC design was nowhere near as well-integrated as it was to become, and IBM never had a tradition of cost-reduction (quite the opposite), but I do wonder what the design criteria were.

[SeanB]

Just boot to the dos prompt, and use debug ( should be there on the disk) and you can use the drive bios direct to setup the disk. From the days before you had a bios over 64k, and had a rom for each board. I probably have memory for that board in my bag of older memory, though they might be SIP modules.

Just think, that those asics and other glue logic took the place of around 30 40 pin DIP packages, the original AT design had a lot of them. The buffers were definitely needed, as the 386SX was pretty poor at driving any bus, it really needed a buffer right next to the chip for anything other than driving a single companion chip. The only difference between the first SX and DX chips was that the DX actually passed the math processor check, so then one pin was pulled high to enable the coprocessor. If you were willing to chance it you could use a SX and simply change the jumper that turned it into a DX, and hope the processor was more or less functional. Never was able to get a working one though.

[calin]

Yeah that keyboard .. I wold have bought the laptop just for that . IBM did made probably one of the best keyboards ever made - Model M. I still have yet to find a keyboard like that made now. Like someone said before there is Unicomp now making a copy .. I think IBM has sold the patent to Lenxmark and then Lenxmark sold it to Unicomp . I actually bought the Classic model from Unicomp ... is not bad but not the same build quality as the old IBM ones. I tried many mechanical keyboard and none of them com even close to Model M to the feel and typing.


Funny enough after I got that I found a original model M made in 1998 I think in UK thrown in the junk bin @ work by some idiot that had no idea what he is throwing away. Ugly, dusty  and full of grime but ..do you remember .. all the keys pop out. Did that gave them a nice bath with detergent and rinse, cleaned up the rest nicely and I have an working original Model M. ... PS2 connector and now Win key. I am typing this post on it ... absolutely down right sexy feeling  .. and the clicky sound .. oooh yes !!! 


And yes these things are heavy as a tank .. the Unicomp modern copy is not nearly as sturdy and heavy as the old ones and the plastic quality is not as good. Hell the 98 made one feels way more solid .. i can kill someone with it and probably will still work (if that is a quality what are you looking for in a keyboard ).


 If I just knew how searched for these things will be in the university , all our labs were running 286 and 386 IBM machines with these KB's .. I remember we started replacing them and literally we had bins full of Model M being thrown away. Idiots .. what can i say 

[kaiserreich]

Just came here to post this after watching this video.

The keyboard in the IBM L40SX is similar to a Unicomp Mighty Mouse/ IBM M4-1
Unicomp no longer sells it, but I think you can still get one from eBay

[Stonent]

After the boot disk configured it, I'd bet it might have booted from the HD.

[Nerobro]

The hard drive is probably ok.  At the time BIOS's needed to know the drive geometry.  if you set that using the setup disk, I bet your data on that drive is just fine. 

Nice laptop Dave.

[Rasz]

The only difference between the first SX and DX chips was that the DX actually passed the math processor check, so then one pin was pulled high to enable the coprocessor. If you were willing to chance it you could use a SX and simply change the jumper that turned it into a DX, and hope the processor was more or less functional. Never was able to get a working one though.

you are thinking 486
386 SX DX was about bus width

[Stonent]

The only difference between the first SX and DX chips was that the DX actually passed the math processor check, so then one pin was pulled high to enable the coprocessor. If you were willing to chance it you could use a SX and simply change the jumper that turned it into a DX, and hope the processor was more or less functional. Never was able to get a working one though.

you are thinking 486
386 SX DX was about bus width

The 386 SX could execute 32 bit x86 instructions but only had a 16 bit bus.

And a little PC history lesson for the day....

The original 386s had some problems with some 32 bit instructions and were recalled basically.  Ones that were certified OK were stamped with a double sigma.



The revised 32 bit safe 386's were renamed 386DX but still had the double sigma stamp.



When the SX came out, the DX became a prominent part of the logo and the double sigma was dropped.



The ones that did not pass were sold as 16bit only processors.

[Rasz]

nice trivia there
I wonder whats the point of that last one, probably only to clear Intel  warehouse of broken silicon. IPC difference between 286 and 386 wasnt mayor and you couldnt use this chip in existing 286 board anyway, so all in all it was a ripoff

My first x86 PC was a am386DX-40 in 1995-96, same year Nokia released a phone with 386 cpu (nokia 9000 communicator). It was so outdated at the time I was able to buy it in a course of two months with my weekend job money. Motherboard first with 4x1MB topless brand 30pin simms (topless probably because they were too cheap for proper ram chips, they used COB packaging) and VGA 512KB trident or oak or something, basically shittiest cheapest I could find on a computer market. Later 40MB Seagate ST-157 with ISA IDE controller (mmm ~4MB/s speed!) and a 'multimedia package' - some terribad soundblaster clone with integrated cdrom controller and 2x speed barely working CDrom. I was soo cheap I used homemade VGA-2-SCART (afair 7400 AND gates adding syncs together) cable with special dos driver that changed horizontal clock. Almost two years using TV as a monitor Doom/Dune/Colonization ran well on this piece of crap.