Strahssis wrote on 2022-06-01, 22:48:

Hi everyone, […]
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Hi everyone,

I started working on a Compaq SLT/286 today. I already successfully did the Dallas clock battery mod so I can use a normal CMOS battery. I ran a cable to a place easily accessible from the outside and I put some RCA connectors in between, so the battery will be easy to disconnect and replace.

Anyways, as expected the hard drive is no longer working and to my surprise it takes a 3,5" 40 pin IDE drive. I was planning to replace it with a CF-to-IDE adapter, but the problem is that the laptop doesn't use molex for power, it uses some 3-pin proprietary cable. Do you guys know this laptop and do guys have a solution for this problem? Maybe someone has the pin-out so I can make an adapter cable for molex? Thank you guys in advance!

All the best,

Miko, Strahssis

Check this thread - Compaq SLT 286

That does help a lot, thank you very much! 😀

Well, I tried a few things, but with no success.

I tried replacing the hard drive with a CF-to-IDE card, while setting the drive type manually to Type 2 (21,4 MB) in the Compaq setup. I tried both a 64 MB and 128 MB CF card. One gave me a 1781 error and the other one a 1782 (see the pictures) on startup. I tried using an old 4 GB drive I had lying around as well, but it gave me the same 1782 error.

Since nothing worked, I tried fixing the original drive. I cleaned off the disintegrating rubbers inside and replaced it with some layers of electrical tape, but the drive did the same as before: it loudly spins up, gets locked into making loud fart noises (not normal hard drive sound) for about 30 seconds, then spins down and tries again. My intervention made no change in the behavior of the drive. In the Compaq diagnostics the drive reports the error code 1700, which means according to the service manual "Fixed disk ID drive types test failed". The service manual tells me to try replacing the hard drive, the hard drive cables and the motherboard, so the document is of no use for this really. The original drive does not report code 1781 or 1782 on startup, so despite what some online sources speculate, I believe the controller on the motherboard is fine.

Can any of you guys help me? I don't really mind what kind of drive ends up in the laptop as long as it works. It would be cool to get the original drive working again, but I'd gladly take the CF option as well.

NB: For future readers of this topic looking for the pin-out of the proprietary hard drive power connector, the center cable is the 12V and the ones on the side are 5V and GND. The GND reports continuity with the metal shield, so it's easy to figure out which one of the other two is the 5V and which one is the GND.

Hello. I was an SLT/286 owner a long long time ago.
It was in the 90s, still, when I had two of them, if memory serves..

Anyway, what I vaguely remember from back then:
a) The pinout of the HDD is different. Maybe it was merely the power cable, not sure.
b) The CMOS Setup was on diskette
c) The BIOS checked for drive manufacturers. Only Conner drives or OEM were accepted.
d) The battery pack included some sort of relay. You can hear it *click*, if you move a strong magnet over the surface.
When completely depleted, the pack won't charge anymore.
e) The SIMMs were a bit proprietary. I've managed one SLT so see 4MB. Worked like a charm in Windows 3.10.

I'm sorry, that's all that comes to mind right now.

SLT 286 and 386 are standard ATA pinout. Only difference is power pins, 5, 12v and ground.

CF cards are not always compatible, Ones that works well for me is WD 512MB and 1GB, you can set the CMOS to use 200MB or 504MB and use fdisk and format it will work.

Cheers,

Thank you for your replies. The power connector pinout is different yes, I figured that one out with the multimeter. I guess the OEM-check explains why the Apple hard drive didn't work.

I looked up those WD CF-cards, but they are like $50 and I can't find them on the used market. I ordered some more old CF-cards second hand. Based on pentiumspeed's reply, I should eventually find one that works. None of my current ones work. Some bigger ones I haven't tried, truth be told, but I think it would be a waste to use 1GB+ capacities on a SLT/286. I'd better save those for 486 builds. Weird thing is, that even the ones that work with my Contura's (which are also very picky about the CF-cards), don't work on the SLT/286.

I also ordered four more used SD-to-IDE adapters for €10,-, which is a steal. I have had some luck with those in the past, so maybe they're also worth a try on the SLT/286.

One more question though: you mention that I can set the CMOS to use 200MB and 504MB, but my diagnostics diskette doesn't provide me with that option. I can only select Type 1 (10,7MB), Type 2 (21,4MB) and Type 4 (71,4MB) and I don't have the option to set the CHS settings manually. So how can I set the CMOS to use other capacities?

Other CF card that works:

Swissbit Industrial

Trenscend industrial I think 266x or 300x Plain ones.

Yes, CF cards are expensive as hard drive are but more reliable than hard drive and easier to find. You can try getting a Seagate or Hitachi 2.5" PATA anywhere from 20GB to 100GB and small 44pin adapter to 40 pin.

Cheers,

Hi, Thanks, appreciate the help! I bought a bulk of CF cards lately. At least one of them has got to work. 😀

Strahssis wrote on 2022-06-01, 22:48:

to my surprise it takes a 3,5" 40 pin IDE drive

we have Compaq (in cooperation with Western DigitalConner) to thank for IDE interface in the first place 😀
Compaq (&WD) came up with IDE ability to query drive for parameters all the way in 1986! No need for tedious manual configuration by typing sectors/heads/tracks etc https://www.os2museum.com/wp/whence-identify-drive/ https://www.os2museum.com/wp/identify-esdi-drive/

Cool! 😁👍

But wait, didn't AMI BIOS from the late 80s support HDD detection in CMOS Setup? 🤔
Some of my 386 PCs have that feature, but I never used it.

Source: https://www.winhistory.de/more/486/486_bios.htm

Jo22 wrote on 2022-08-18, 06:55:

Cool! 😁👍
But wait, didn't AMI BIOS from the late 80s support HDD detection in CMOS Setup? 🤔

Can you find one? Those screenshots are from 1993 bios. Michal would probably love to get his hands on some very early IDE autodetection bios examples.

rasz_pl wrote on 2022-08-18, 08:42:

Jo22 wrote on 2022-08-18, 06:55:

Cool! 😁👍
But wait, didn't AMI BIOS from the late 80s support HDD detection in CMOS Setup? 🤔

Can you find one? Those screenshots are from 1993 bios. Michal would probably love to get his hands on some very early IDE autodetection bios examples.

Um, yes and no. I do have a "few" 386 motherboards and a prommer, but no space to build up a test bench.
The whole home is crowded with stuff at the time. 😅

Anyway, I'll check the ROM labels on the boards.
Maybe I'll do some dumps "out of the blue" (do you say so in English) ?

Btw, I think AMI BIOS does support it since 1992, at least.

https://www.youtube.com/watch?v=xtnQu_Iwzxw

Older versions from 1989/1990 do have a "Hard Disk Setup" entry in main menu.

However, I don't know if that's for low-level formatting and interleaving setttings only.

But there's a catch with the dates, also.
The copyright date may also relate to the compile time or the motherboard release.

AMI BIOS was a modular thing, ie, it was made up from individual components (not s monolithic piece of code, except when deployed as a finalized ROM file).
By using a software kit, an AMI BIOS could be assembled by AMI or AMI's customers, as needed. With options hidden/disabled, routines removed, etc.
So a BIOS released in 1993 could be made with code that originally has/had a copyright from, say, 1991.

However, I'm just a layman and so I'm speaking under correction.
Please double check what I said.

Jo22 wrote on 2022-08-18, 09:19:

Um, yes and no. I do have a "few" 386 motherboards and a prommer, but no space to build up a test bench. The whole home is crowd […]
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Um, yes and no. I do have a "few" 386 motherboards and a prommer, but no space to build up a test bench.
The whole home is crowded with stuff at the time. 😅

Anyway, I'll check the ROM labels on the boards.
Maybe I'll do some dumps "out of the blue" (do you say so in English) ?

just a model number would suffice if you happen to stumble on something from 80s

Jo22 wrote on 2022-08-18, 09:19:

Btw, I think AMI BIOS does support it since 1992, at least.

Early nineties sounds more realistic for ami/award. This functionality wasnt even universally supported by all hdd vendors up to nineties. https://www.os2museum.com/wp/identify-ancient-drive/
Compaq had the comfort of tightly controlling its suppliers. They could be sure about availability and actual formatting of data returned by IDENTIFY DRIVE command - there was endianness confusion among vendors all the way to ~1996 https://www.os2museum.com/wp/vague-standards-are-trouble/