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View Full Version : IBM PS/2 model 55 - FDD works, HDD is present, will not boot from HDD



PeterNY
July 7th, 2011, 05:11 PM
My PS/2 model 55 has a working FDD and I can boot from FDD and then read the HDD just fine: including running COMMAND from it and starting Windows 3.1. It will not boot from HDD. I tried the IBM reference disk and FDISK/MBR.

Any suggestions? :mrgreen:

modem7
July 7th, 2011, 05:13 PM
Run FDISK and see if the partition that you want to boot from is marked as Active.

PeterNY
July 7th, 2011, 06:01 PM
Run FDISK and see if the partition that you want to boot from is marked as Active.
I did: no luck.
Turns out the new DS12887A I put in does not retain settings. When I power off it does not remember. I checked the one pin that needs to be bent/removed. Oh well. :-)

BTW: moderators: I erroneously posted this under PCs where it should be under the section for 80386 and above.

DOS lives on!!
July 8th, 2011, 03:37 AM
I did: no luck.
Turns out the new DS12887A I put in does not retain settings. When I power off it does not remember. I checked the one pin that needs to be bent/removed.
When it comes to aggravating people, the DS1287 and DS12887 batteries are definetely first in line. And then Compaq decided to solder them to the motherboard.

PeterNY
July 8th, 2011, 04:34 AM
When it comes to aggravating people, the DS1287 and DS12887 batteries are definetely first in line. And then Compaq decided to solder them to the motherboard.

Right. I put the DS1887A back in the IBM PS/2 model 30 286 and it retains settings there. :)

kishy
July 8th, 2011, 07:47 AM
Make sure that's the right model RTC module...12887 replaces 1287. An 'A' or '+' on the end can indicate an incompatible model that will either sometimes work, or not work at all.

So...whatever the original was, make sure the new one you have installed is compatible. The A seems to designate that one of the pins is designed to be a reset pin - so depending on how the socket in the 55 is wired, it may be that it works fine but the system is inadvertently resetting the chip constantly.

http://www.100y.com.tw/pdf_file/MAXIM_DS12887A.pdf

PeterNY
July 8th, 2011, 11:27 AM
Make sure that's the right model RTC module...12887 replaces 1287. An 'A' or '+' on the end can indicate an incompatible model that will either sometimes work, or not work at all.

So...whatever the original was, make sure the new one you have installed is compatible. The A seems to designate that one of the pins is designed to be a reset pin - so depending on how the socket in the 55 is wired, it may be that it works fine but the system is inadvertently resetting the chip constantly.

http://www.100y.com.tw/pdf_file/MAXIM_DS12887A.pdf

Thank you. I will check it this evening. :)

jharre
July 11th, 2011, 07:47 PM
I had the same problem with my 55sx not booting from the HD. Of course the Dallas 1287 was nearly dead and kept tossing up 161 and 163 errors.

Followed the instructions at http://www.mcamafia.de/mcapage0/dsrework.htm to grind a couple notches in mine and wire in a coin battery 'replacement' (which works quite well!) The reworked battery still had the same problem! The solution was to remove the coin battery and short the battery terminals for a few minutes. Once I did that, a 162 error appeared and running the reference disk solved the problem.

Also saw this article: http://www.ibmmuseum.com/ohlandl/8555/8555_Planar.html that uses Debug to achieve the same effect. Didn't get to try that one, but it might work better for you.

<*> Jim

jharre
July 11th, 2011, 08:07 PM
The description for pin 21 in the datasheet for the 12887/12887A notes:

Active-Low RAM Clear. The RCLR pin is used to clear (set to logic 1) all the
general-purpose RAM, but does not affect the RAM associated with the RTC. To
clear the RAM, RCLR must be forced to an input logic 0 during battery-backup
mode when VCC is not applied. The RCLR function is designed to be used
through a human interface (shorting to ground manually or by a switch) and not
to be driven with external buffers. This pin is internally pulled up. Do not use an
external pullup resistor on this pin.

So, it looks like you could just bend pin 21 out so it doesn't touch the socket and it would work just fine.

<*> Jim

PeterNY
July 14th, 2011, 07:25 AM
I bought 50 DS1287 chips. As soon as they arrive I will hopefully find one that still works. When I have chips left I will offer them up for cheap sale here.

PeterNY
July 14th, 2011, 07:26 AM
I had the same problem with my 55sx not booting from the HD. Of course the Dallas 1287 was nearly dead and kept tossing up 161 and 163 errors.

Thank you. I am not big on home engineering. :)

PeterNY
July 14th, 2011, 07:27 AM
So, it looks like you could just bend pin 21 out so it doesn't touch the socket and it would work just fine.
Right. That is how it works in the 8530 286 but not in the 8555 SX. :(

IBMMuseum
July 14th, 2011, 08:17 AM
Right. That is how it works in the 8530 286 but not in the 8555 SX. :(

Some PS/2 models had a different location for the century byte in the RTC CMOS than the IBM AT or clones. Dallas updated their chips for Y2K (one hardware issue was that the years rolling over did not increment the century counter), but you have to be careful which replacement model you get. I don't think that is the problem here however.

The 55SX was notorious for the heavy EC wirings to fix initial faults, and there were a few different planars and risers to get the system more consistent...

PeterNY
July 14th, 2011, 09:14 AM
Some PS/2 models had a different location for the century byte in the RTC CMOS than the IBM AT or clones. Dallas updated their chips for Y2K (one hardware issue was that the years rolling over did not increment the century counter), but you have to be careful which replacement model you get. I don't think that is the problem here however.

The 55SX was notorious for the heavy EC wirings to fix initial faults, and there were a few different planars and risers to get the system more consistent...
Thank you for the update.

Back in business! The 3rd DS1287 I tried finally did the job! The system is back online! :D

jharre
July 14th, 2011, 07:21 PM
Yahoo! What's different about the third one you tried?

PeterNY
July 15th, 2011, 04:40 AM
Yahoo! What's different about the third one you tried?

I bought 50 DS1287 chips so my guess is that the first 2 were already dead. The bulk package I bought were stripped from recycled machines so I guess most will not work but my assumption was that some would.