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ShadowStormX
October 6th, 2014, 06:24 PM
Hello all,

I recently picked up a IBM 5150. I am new at retro computing...

How can I load DOS 3.1 from floppy drive. The computer would keep poping up 409C 201. I thought this means memory error somewhere.

However...if I take the disk out and turned on the computer, it boots into IBM Basic 1.10.... What am I doing wrong?

This kind of computer uses 2 Full-Height original floppy drive, so no hard drive.

Stone
October 7th, 2014, 12:06 PM
It does mean a memory error. 409C is the hex address of the error. I think that's on an expansion board. The reason it boots to basic without a disk is that it doesn't need that bad memory to run BASIC. But it does to run DOS. If you track down the chip that corresponds to 409C and replace it you might get lucky.

SpidersWeb
October 7th, 2014, 01:07 PM
Double check that error code, if it really is 409C then that'd be memory on an expansion card which you could pull out / replace. (40xx = 256KB).
DOS 3.1 should run with 256KB no problem (I use MS DOS 3.3 on my 256KB clones).

If sorting that out doesn't help, I'd test the disk works in another machine, and preferably using the same drive (e.g. move it between case) just to be sure that part of it is working.

modem7
October 7th, 2014, 11:00 PM
Lots of IBM 5150 information at http://www.minuszerodegrees.net
From that site:

The format of a RAM error is "bbxx 201". An example is "0510 201".
The "bb" portion of "bbxx" indicates which 4 KB block contains the faulty RAM.
The "xx" portion of "bbxx" indicates which bit in the block is the faulty one.

So yes, the 40 in your 409C indicates an error at the 256 KB address. The 9C in your 409C indicates that bits 2,3,4 and 7 are faulty.

It could be that you have that many bits in error in the block of RAM at 256 KB. However, sometimes, when a large number of bits show in error, it is the result of the power on self test (POST) checking RAM that does not exist.

I think that the first thing you should do is to establish what RAM is in your 5150 (motherboard + any RAM expansion cards) and then verify that the various configuration switches (motherboard + any RAM expansion cards) are set correctly for that.

ShadowStormX
October 8th, 2014, 05:24 PM
Lots of IBM 5150 information at http://www.minuszerodegrees.net
From that site:

The format of a RAM error is "bbxx 201". An example is "0510 201".
The "bb" portion of "bbxx" indicates which 4 KB block contains the faulty RAM.
The "xx" portion of "bbxx" indicates which bit in the block is the faulty one.

So yes, the 40 in your 409C indicates an error at the 256 KB address. The 9C in your 409C indicates that bits 2,3,4 and 7 are faulty.

It could be that you have that many bits in error in the block of RAM at 256 KB. However, sometimes, when a large number of bits show in error, it is the result of the power on self test (POST) checking RAM that does not exist.

I think that the first thing you should do is to establish what RAM is in your 5150 (motherboard + any RAM expansion cards) and then verify that the various configuration switches (motherboard + any RAM expansion cards) are set correctly for that.

Thanks, I'll be checking the computer out tomorrow. But...when I saw that "C", it wasn't in that list of bits. Where did you find that information?

I checked this part: http://www.minuszerodegrees.net/5150/ram/5150_ram_64_256.htm

modem7
October 10th, 2014, 08:10 PM
Thanks, I'll be checking the computer out tomorrow. But...when I saw that "C", it wasn't in that list of bits. Where did you find that information?
I checked this part: http://www.minuszerodegrees.net/5150/ram/5150_ram_64_256.htm
Per that web page (which I should enhance), the figures are in hex.
So, one way work out the bits is simply to convert to binary, and from that, note which bits are set:

9C hex = 10011100 binary

bit = 7 6 5 4 3 2 1 0
----+-----------------
9C = 1 0 0 1 1 1 0 0

ShadowStormX
October 12th, 2014, 06:35 AM
Ah interesting...thanks modem7.

Update, I removed all expansion card on the 5150, except the color graphics. I still get an error...but this time it is 40D8 201. However...on the back of it, there's a switch. I switched it and I would get this error code 4098 201.

After removing all other expansion cards, except the color graphics card...it didn't say Parity Check 1 or 2, just the error pops up.

All I know is that all the chips on the color graphics are soldered on, except two big chips which I tried re-seating them.

modem7
October 12th, 2014, 11:27 PM
All I know is that all the chips on the color graphics are soldered on, except two big chips which I tried re-seating them.
What you need to be concerned about are cards that provide conventional memory; RAM below the 640 KB address.
RAM on video cards is above the 640 KB address, so ignore that RAM.

We don't know if this stage whether any of your expansion cards are providing any conventional memory. If you provide photos of the cards, then we can inform you.


Update, I removed all expansion card on the 5150, except the color graphics. I still get an error...but this time it is 40D8 201.
With the expansion cards out, the only possible conventional memory is the RAM on the '64KB-256KB' motherboard, and on that, you have 256 KB fitted.
I deduce from the "40" in your "40D8 201" that the motherboard thinks that there is more than 256 KB of conventional memory in the 5150 (motherboard RAM + any RAM expansion cards).

When a 5150 owner adds/removes conventional memory, the owner configures the switches on the SW2 switch block to match the total amount of conventional memory.
With the expansion cards out, SW2 needs to be set to 256 KB.
So, set the SW2 switches per the '256K Total Memory' line on page 5-37 of the manual at [here (http://www.minuszerodegrees.net/manuals/IBM_5150_Guide_to_Operations_6322510_APR84.pdf)].

If it is later found that one (or more) of your expansion cards is providing conventional memory, then we can work out a revised setting for SW2.