486 problem

There might be several ways, including disconnecting all drives to the MB. Since no drive is detected and therefore no operating system, an error message should appear. Another way is to hold down any key on the keyboard and many will give an error message regarding the keyboard having failed due to a stuck key. The message generally allows you access to CMOS setup at that time.

schreef in bericht news: snipped-for-privacy@l53g2000cwa.googlegroups.com...

Best thing should be the manual of the 486 board. Ever saw a German site with lots of manuals of old boards. Without manual you can at least strip the board to the minimum. Remove all boards (especially the MFM controller but all others as well) so you have only the video and the keyboard left. You should be able to enter the BIOS setup now.

Depending on the board you may be able to disable the IDE-controller(s) in the BIOS. Some of the old boards used straps for it, on others you cannot disable the controller at all. That's a real problem as both controllers (IDE and MFM) use the same addresses (most of the times) so you cannot have both enabled. Some controllers has straps to set alternate addresses but most of them do not have these features.

Once on air, you can build up the machine again.

petrus bitbyter

On Thu, 01 Feb 2007 14:58:45 -0800, snipped-for-privacy@yahoo.com Has Frothed:

Try a fresh battery.

Did you remove the MFM controller? If there's a conflict, it may be preventing BIOS from working properly. You should disable the IDE before reinstalling the MFM controller.

Try leaving the battery out all night. Andy Cuffe

snipped-for-privacy@gmail.com

No it doesn't.

Graham

possibly the bios has reset and the "display F2" setting changed causing it not to appear but the function is still there...push F2 at the right time...or is it Delete???

i may have parts you are welcome to for the shipping if you need anything

Just keep quickly hitting F2 while it does its POST, it may get you into the BIOS.

The CMOS settings are not generally stored in the BIOS chip.

If hitting F2 repeatedly does not work, disconnect the battery and leave overnight as Andy Cuffe suggested.

Morse

One trick I used to use on obstinate 386es and 486es to get into the CMOS was to insert a 3.5' floppy jacket with no disk inside it! Take a scrap disk, remove the shutter and spring, split the edge you see when its in the drive with a knife and pull out the disk from the jacket. It used to work *most* of the time and usually saved opening the case. Worth a try.

You *MUST* disable the onboard IDE if you want to run a standard MFM controller but its possible you wont be able to run the MFM controller on a board with onboard IDE as the BIOS may be expecting a more advanced controller. You may well need to find a board *without* onboard drive controllers. Its als possible it needs to time-out on the IDE controller before you'll get the press F2 message. I remember one machine that would take over 5 minutes to decide it *really* couldn't boot and give me a F1 to continue, F2 to setup message.

Once you get it going, I strongly reccomend transferring the programs to a newer technology drive. If they are DOS version dependent, dont forget to make a boot flopy and copy the SYS, FDISK, ATTRIB, EDLIN and FORMAT commands onto it as well.

On 1 Feb 2007 14:58:45 -0800, " snipped-for-privacy@yahoo.com" put finger to keyboard and composed:

I thought Ctrl-S or Ctrl-Alt-Esc were the appropriate keys.

The *nonvolatile* BIOS chip is either an EPROM or flash EEPROM. The

Boot from a floppy, and then trash the CMOS RAM contents using DOS debug.exe, as described here:

- Franc Zabkar

Hi!

'Del' (the Key below 'Insert'), or pressing F10 should do the trick. Immediately after reset or turn-on.

F2 appears AFAIK, only when the BIOS CMOS Values (BIOS settings) are dumped, e.g. due to a empty battery, or changed hardware settings. At least with Compaq IBM-PC's and Laptop POST-Messages (POST = First Start, Initialize).

Best Regards,

Daniel Mandic

Hold down the "shift" key on the keyboard. It may force an error and let you back into the bios.

Lenny, most of the 486 motherboards I've worked with were too fast to support the MFM drive controllers. Some 386 boards were flaky, or didn't work at all when they were new. The 16 bit MFM controllers were made for 286 computers, and IDE was introduced before the 386 became popular.

On Wed, 07 Feb 2007 15:25:18 +0000, Michael A. Terrell Has Frothed:

IIRC you are correct. BTW MFM is stil the recording method for floppies.

It was the most popular method, but there were a few other floppy data formats over the years.

As a side note, IDE drives are RLL format, with a built in controller. The IDE port is a simple interface to connect the controller to the computer's various busses.

Run length limited compression. I recall when the 32 MB HDs came out. That was the first HD I bought on an AT expansion card in fact. Probably the first 3 1/2" drives too. They were actually 20MB MFM drives with an RLL controller. The MFM is just modified frequency modulation IIRC - unrelated to the RLL, so they were MFM RLL drives.

The physical IDE connection wasn't much more than an AT bus expansion connector in the early days AIUI.

Graham

On Thu, 08 Feb 2007 16:11:12 +0000, Michael A. Terrell Has Frothed:

I remember the MFM/RLL drives. Some MFM could be low level formatted using an RLL controller

debug

g = c:8000

IIRC

Graham

The difference in the actual drives was that the media was tested and certified for RLL.

connector

Read what I said, above and tell me I'm saying anything different.

Yes, but some would format ok, then quickly become unusable because they didn't reliably support the higher data rate. That was why they assigned different model numbers to what was basically the same drive, but tested and certified to the RLL requirements.