The compaq BIOS with these machines resides on their own little partition that is created at the beginning of the drive structure. If you have formatted the drive or switched it, you probably do not have this partition anymore, which results in you being unable to load the BIOS Setup Program.

You need to either reinstall the diagnostic partition (optional) or simply boot off the "setup/diagnostic" disk that is compatible with your 386s/20

If the checksum error persists while creating the diagnostic disk, try with another diskette.

I have tried with another floppy disk and it has finished transferring the information and it has not given error.

I have managed to enter the setup with this diskette.

Part by part:

1. The stack. I've been measuring voltages and he gives me 2.72. I think it's okay. I have also measured voltages in the dallas and it seems fine. Leg 16 with 22 gives me 2.72.

2. I have put the HD in another pc and it does not go.

3. I have taken a HD of 40mbs that I have and it works well. I have put it and when entering the Setup (bios), I have detected it as one of the models, I think the type 22 (40mbs)

4. I'm still stuck, because when I start, I get error 162 again and I do not recognize the hd. If I start with a floppy disk of msdos and do a fdisk, it tells me that there is no hard disk.

5. Photos of the setup:

When you access:

If you indicate "n", as it is, enter the setup. If you indicate "and", the following screen appears

You enter the setup and you are:

By changing the values ​​and pressing f3, you are supposed to save the configuration. But it is still the same.

any ideas?

Either the battery voltage is too low to save the settings (I dont think so, 2.72 Volts should be enough), OR the compaq bios is not accepting either the drive OR the values you put in the bios.

What settings are not being saved? All the settings (like you changing COM settings for example), or ONLY the drive settings (type, cyl, heads, etc.)

IF only the drive settings are not being saved (revert back to original settings after reboot) it could mean that it doesnt accept the values.

I have several Compaq laptops that all have this behaviour of not saving DRIVE settings that are changed in BIOS. I have to use overlay software for these computers to make them work with replaced HDDs.

the problem was the dallas himself. I have changed it for another and now it saves the configuration. the problem now is that the pc does not start from the hd, only from A and B. if I start from A with a msdos, I can access C. I have formatted C and I have installed msdos 6.22. but the beginning remains the same. without a diskette, it does not read from C and it remains hung

Perro wrote:

without a diskette, it does not read from C and it remains hung

There is no bios, only system configuration on NVRAM part of the RTC.

This used to happen to me all the time when configuring the Systempro... the system hung when trying to load the OS after just re-inserting the HD. I made a thread specifically about this (below)... but not many people appreciated this with Compaq, system configuration is not as easy as custom systems.

The Systempro Project; The Bios

I remember I had to physically install the fixed disk last every time, and run System Configuration again, just for the HD.

I've made the hd bootable. for this, I had to start from two 3.1 and make a fdisk. delete the partition and create it again. format (up to 32mbs) and transfer the system. in this way, I can start in C.

386_junkie wrote:

There is no bios, only system configuration on NVRAM part of the RTC. […]
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Perro wrote:

without a diskette, it does not read from C and it remains hung

There is no bios, only system configuration on NVRAM part of the RTC.

This used to happen to me all the time when configuring the Systempro... the system hung when trying to load the OS after just re-inserting the HD. I made a thread specifically about this (below)... but not many people appreciated this with Compaq, system configuration is not as easy as custom systems.

The Systempro Project; The Bios

I remember I had to physically install the fixed disk last every time, and run System Configuration again, just for the HD.

Perro wrote:

I've made the hd bootable. for this, I had to start from two 3.1 and make a fdisk. delete the partition and create it again. format (up to 32mbs) and transfer the system. in this way, I can start in C.

Hmm it seems some compaq systems like this one are very picky when it comes to the HDD. It kind of reminds me of the PS/2 L40SX Reference diskette that needs to be loaded after each change made to the system, EVEN if you didnt need the reference disk tools to even make aforementioned change.

My Packard Bell Pack-Mate 28 Plus does this as well when I install an HDD above 2GB (I can only enter up to 4000 cylinders and LZ), and if it's not configured manually (auto-detect), it would say the HDD is smaller in size (ex: 773MB instead of at least 2GB). Also, when the CMOS battery dies, it never boots from the HDD, only the floppy drive, even if I save the settings.

BIOS limitations, BIOS limitations everywhere. The other 486 I had between 1994 and 2012 had the limitation size for the HDD up to 7.8GB if the HDD was bigger than it supports, and my Socket 7 system supports up to 32GB space (limited), or 7.8GB if it's a little over 32GB.

I solved it with an 80mbs hd. the problem is that in the bios-setup has only 55 types and can not be entered manually, as in a generic bios. Even so, yesterday everything became confused and I had to start over. Now, it seems to be stable. Compaq is a very complicated brand. Almost I prefer ibm or amstrad.

Perro wrote:

I solved it with an 80mbs hd. the problem is that in the bios-setup has only 55 types and can not be entered manually, as in a generic bios. Even so, yesterday everything became confused and I had to start over. Now, it seems to be stable. Compaq is a very complicated brand. Almost I prefer ibm or amstrad.

If you ever want to change the drive as in using a bigger one that is apparently not supported by your BIOS (or even CF/SD-adapters), then you can always use Drive Overlay Software.

386_junkie wrote:

There is no bios, only system configuration on NVRAM part of the RTC.

Small correction: There's no CMOS Setup Utility built in oldish Compaq BIOSes/Firmware. If there wasn't BIOS/Firmware then the machine couldn't boot.

Quick question: Is there any site to order those Dallas custom batteries for replacement? I need few, it seems I cannot customize myself..

Thanks a lot.