Old 486 computer reference disk

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Old 486 computer reference disk

Postby techgnome » Sat Jan 24, 2015 1:53 pm

Hello folks, I have an old Epson Equity 486DX2-50 that I am attempting to resurrect. The Dallas CMOS battery module was replaced with a brand new one. I tried to boot up and got a LOUD beep demanding a "reference disk". (Which is really a SETUP disk) I have searched high and low and cannot find one, even from the Epson company itself. Without it, I cannot get the system to recognize the hard drive, and other options. Does anyone know where I can obtain the files from that disk? I will be VERY grateful!! Thanks!
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Re: Old 486 computer reference disk

Postby Karlsweldt » Sat Jan 24, 2015 5:13 pm

Welcome to Motherboards.org.
That is an old rascal! Lucky you were able to get a new BIOS battery chip. Most were soldered to the board, not in a socket.
As to setting the BIOS pages, perhaps a key combination of Ctrl. + Alt. + Enter, or Ctrl. + Alt. + S or Ctrl. + Alt. + Insert may bring up the BIOS pages. But some of the older models did require a special setup file to set the BIOS. If interested in specs on some of the 486 models, here is a PDF file.. https://files.support.epson.com/pdf/e4dx5p/e4dx5ppg.pdf
Here is another PDF file I found.. https://files.support.epson.com/pdf/psb/psb.s-0155.pdf
See page 4, mentions the "delete" key just as the POST process is about to finish. Maybe?

Will have to check my archives, may have a BIOS access file that may work. It requires a 1.44 floppy, formatted and bootable to DOS 5.0, with very basic boot level.. and the BIOS access command.
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Re: Old 486 computer reference disk

Postby evasive » Sun Jan 25, 2015 3:00 am

eww sounds like an olivetti-like creature... ok, here we go for a deep dive into the archives...
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Re: Old 486 computer reference disk

Postby techgnome » Sun Jan 25, 2015 11:58 am

Thanks Karlsweldt and evasive! This critter is going to be tricky! I got it to boot up and run off floppy and have a DOS disk so it does run! Actually, I work at an electronics manufacturing company so removing the Dallas module was easy. I also installed a socket and the modules are in stock here!! Once again I thank you for your help!
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Re: Old 486 computer reference disk

Postby Karlsweldt » Sun Jan 25, 2015 5:39 pm

Sounds like you have awakened an old spirit! Those Dallas Real-Time chips have a battery on the top, with the clock crystal. There are three versions, two are interchangeable. If you want to experiment, the cap of the chip can be ground off and get access to the battery leads for an external battery, or glue a standard CR2032 battery saddle to it.
Dallas-RTC-chip-fix: http://www.mcamafia.de/mcapage0/dsrework.htm
DOS 5.0 should have no problems with the machine, even DOS 6.22 may work well.
As to a hard drive.. may be difficult to find one within the BIOS limits, but making the primary partition within the BIOS limits can allow a larger drive. As to the heads, sectors, and tracks.. you may be limited to 17 sectors per track, or up to 53 sectors. If you can't get a hard drive to be compatible, do the head/sector trick. Halve the sectors, double the head count! For a 6 head, 63 sector drive, change to 12 head, 32 sector.
Put those counts in the #47 or "user" type slot. Don't use any bias pre-loads (precomp).
If not familiar with the old DOS settings, you will need an auotexec.bat and config.sys file.
Can post the basic ones if wanted. The base memory needs as much of 640K to allow programming to operate properly. Memory controls, drivers and other commands can be loaded to the upper memory bank to keep as much of the base memory free.

Have fun!
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Re: Old 486 computer reference disk

Postby evasive » Mon Jan 26, 2015 1:56 am

a 486DX2-50 if feeding it with enough memory, will run windows 95 OSR2 rather nicely.

@techgnome: what did you have to do to make it come back to life? As to help out other people with the same or a similar problem...
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Re: Old 486 computer reference disk

Postby techgnome » Mon Jan 26, 2015 11:44 am

Thanks for the info, Karlsweldt on that Dallas module. I actually installed a brand new one that we have available at the job! Believe it or not, they still make them!!
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Re: Old 486 computer reference disk

Postby techgnome » Mon Jan 26, 2015 11:59 am

@evasive, the old machine still has the original hard drive in it, I just cannot access it without the "reference disk".

To get the thing working, I had to first change the Dallas module. Then, when I fired it up, it just stopped and asked for the reference disk. Since I didn't have one, I just shut the thing down. Next day I did the same thing, except I let it stay on. It took perhaps 2 or 3 full minutes for it to emit a frighteningly loud BEEP, then it prompted to install a system disk in the floppy drive. I made a DOS disk from a machine running Win XP by typing the "sys a:". At that point I could utilize the computer by running a program from another floppy.

I actually need this machine to run some very old DOS stuff, so Windows is not needed. Being able to utilize the hard drive would make things a LOT easier.
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Re: Old 486 computer reference disk

Postby evasive » Wed Jan 28, 2015 7:07 am

ok you need the setup disk to change the bios to see the harddisk. Is there any more info on the actual system model, typenumbers?
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Re: Old 486 computer reference disk

Postby Karlsweldt » Wed Jan 28, 2015 5:15 pm

The hard drive should have a label with the stats on it.. heads, sectors, tracks.. and capacity. Plus maybe a date it was made. There should also be a diagram of how to set the jumpers for master or slave. Some older hard drives are not really compatible with others. But most are. For an older 486 system, a 40-wire data ribbon is best for IDE needs.
As to formatting a floppy for any computer, the basic format is FAT-12. The BIOS cannot read a higher FAT format.
You can do a FAT-12 format from Win XP if in command-prompt mode.. but not while the OS is dominant.
{format a: /u/s} is the basic command.
http://www.bootdisk.com/ has a large variety of boot disk files. And other 'goodies'.
That old beast may work well if Win 98SE basics are installed as a DOS basis. Most commands are in a 'command' folder, others are in the Windows folder. I keep an old Creative Blaster tower with Win 98SE as my "DOS" machine.. mainly for old games.
Those old games may require an IRQ of 5 or 7 for audio.
Have you tried the various key combos I suggested, even the [delete] key just before the POST process starts?

I did find those older BIOS setup files, but not sure if they will play nicely with a 486 system. Were intended for proprietary 286 and 386 systems.
PM me if you want the zipped files.
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