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Couple of questions about 5150

int 21h

Experienced Member
Joined
Feb 9, 2012
Messages
148
Location
Limerick, Ireland
Hi all,
Bought an XT on eBay but a 5150 arrived instead (I guess the seller didn't know it was a 5150, the picture was blurry).
Sold as spares or repairs.
When I powered it on at work it threw garbage up on the screen ( I didn't have any disks with me, I wasn't expecting it to arrive until tomorrow at the earliest)
IMG_0353.jpg


It booted fine with a DOS disk in it when I turned it on at home a few hours later.
I decided to investigation what the cause of the garbage was as it was supposedly stored in a shed for many decades. I removed a few DIP rams which had filthy contacts and small amounts of corrosion. To cut a long story short does anyone know where I can get a replacement MOSTEK 8225 (MK4116N-3GP) as one of the contacts simply fell off. As well as that does anyone know if dirty contacts will have caused that stuff to appear on the screen in the first place?
 
Dirty or corroded contacts on RAM could be one cause of the problem, but until you get the replacement...
I'd post a WTB for a couple of 4116's on the board and see if there are any takers.
patscc
 
Dirty or corroded contacts on RAM could be one cause of the problem, but until you get the replacement...
I'd post a WTB for a couple of 4116's on the board and see if there are any takers.
patscc
Ah I didn't realize that. I thought you had to replace it with the exact same model number chip (still fairly new to all this!). I had trouble finding the "MK4116N-3GP".
So any 4116 ram chip will do then?
 
Yeah, as long as it's not a slower speed, you should be fine. Most chips can be cross-referenced to parts from other suppliers.
If you want to get fancy, just "WTB: a couple of 4116's for IBM 5150 16k motherboard", and most people will know what you're talking about.
patscc
 
Maybe the problem is corrosion on the sockets, before buying anything, take a deep look. By the way, it's pretty easy to find your IC.
Try to reseat RAM. And please tell what is your board version, should be written near the memory.
 
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I don't think it's necessarily a ram issue but it might be a rom issue. You said that when you booted it without a disk you got the garbage but with a disk it worked ok, right? That sure sounds like a bad rom basic chip. You realize that when that machine doesn't find a bootable disk it defaults to rom to boot basic and that's the scenario you described.
 
My advice is:

Remove every card from your system, only leave the video card. Test the computer. Problem? Remove the video card, clean the contacts, put it again, test again, problem? Remove the extra memory chips, leave your board with only 64KB (I think that you can't remove all banks, since bank 0 is soldered), do the necessary jumper/dip changes, test, problem? Post your results here.

BUT if the system works ok with a boot disk, reseat the ROM chip.
 
That sure sounds like a bad rom basic chip.
Which on a 5150 motherboard is split over 4 chips: U29 to U32

Remove the extra memory chips, leave your board with only 64KB (I think that you can't remove all banks, since bank 0 is soldered), do the necessary jumper/dip changes, test, problem? Post your results here.
The OP is sure to have the later version of the 5150 motherboard (the 64K-256K one). That contains the 10/27/82 edition of the BIOS, which has bugs that prevent proper operation if less than 4 banks of RAM are present. Details [here]. However, for the purposes of experimentation, it will be fine because something is still shown on screen.
 
If the 5150 motherboard uses 4116 memory chips its the 16-64KB version.
The 64-256KB motherboard uses 4164 memory chips.

The best place to pickup replacement chips is ebay. I purchased
some TMS4116 chips awhile back for a good price. I see lots of MK4116
and TMS4116 listed, prices average between $1-$2 per chip. I'd suggest
purchasing some extras....first remove all your existing chips and inspect
to see if any other leads are broken before ordering.
 
Hi guys,
Yeah it's the 16kb-64kb motherboard. Living in Ireland so when I did an eBay search I got nothing (never occurred to me to try .com site as well!)
Is it OK to start it up with one of the 4116 chips missing? I've ordered a few of these chips but it could take a week or so to arrive.
 
Living in Ireland and so when I did an eBay search nothing showed (never thought to use the .com site!) Anyway I'v ordered a few replacement chips so thanks for that guys! Is it safe to turn on with one of the RAM chips in Bank 1 missing? (it's in the row of chips that are isolated from the rest near the speaker). It is indeed a 16kb-64kb board too.
Also about the ROM thing, when I had a non-system disk inserted (after I got dos running and turned it off) instead of telling me it was a non system disk it outputted
"N
D
R"
And when I pressed enter it displayed the same thing under that. I put in a system disk and it booted fine
 
Is it safe to turn on with one of the RAM chips in Bank 1 missing? (it's in the row of chips that are isolated from the rest near the speaker).
Well, it won't cause damage, if that is what you mean.

It is indeed a 16kb-64kb board too.
Chips U29 to U32 are the BASIC ROMs. Chip U33 is the BIOS ROM.
What is the seven digit number on U33 ?

5700051 = First BIOS revision
5700671 = Second BIOS revision
1501476 = Third BIOS revision

Also about the ROM thing, when I had a non-system disk inserted (after I got dos running and turned it off)
So the "displays as expected using DOS boot disk, otherwise display corrupted" symptom is repeatable.

Therefore, I would expect that irrespective of whether or not you have a DOS boot disk inserted, on power on of the 5150, there is a blinking cursor in the top-left corner of the screen.

If one or more of the BASIC ROMs were damaged (or had poor contact with the motherboard) then I would expect your 5150 to have displayed an error like "F600 ROM".

Right now, you will be seeing a 201 type error on power on due to the missing RAM chip. Are you seeing other errors? The trouble is, you won't see the word "Error" - just things like "201", "301", "F600 ROM", "F800 ROM".
 
Also about the ROM thing, when I had a non-system disk inserted (after I got dos running and turned it off) instead of telling me it was a non system disk it outputted
"N
D
R"
And when I pressed enter it displayed the same thing under that. I put in a system disk and it booted fine
The "Non-system disk or disk error" message is not something that the computer displays - its something that DOS displays when it starts.

So, if you try to boot from a blank floppy, the 5150 will see nothing on the floppy and go on to try a boot to C:, and then if that fails, run BASIC.

"Non-system disk or disk error" would be produced if the 5150 saw a DOS boot sector on the floppy, passed execution to it, and the code in the boot sector failed to locate certain additional components required to boot. It would be the boot sector code on the floppy producing "Non-system disk or disk error".
 
Hi there,
Yeah the blinking cursor does appear (I havn't powered it on since the RAM chip contactor broke). Didn't realize the thing about the DOS message, that was an assumption by me! The BIOS revision is the 5700671. I'll have a look at it again when I'm back in work tomorrow morning!
 
The BIOS revision is the 5700671.
In case it becomes relevant later for you, that BIOS revision has two significant limitations:

* No more than a total of 544 KB of RAM is recognised (because, by design, only the first 4 switches on switch block SW2 are used).
* The BIOS expansion ROM in cards that have one is not recognised. Examples: EGA/VGA cards, hard disk controllers.
 
Basically, with this BIOS revision, no hard drives at all?
And about the 544 KB limit, this applies to expansion cards?
 
Yes indeed, I did the same thing with my 5150--I used an 8" Shugart SA1002 hard drive connected to a WD1001 controller connected to a little board I made myself in the 5150. 4 whole megabytes! I had to write the driver and formatter, but it worked for a couple of years until I moved up to a different system. I still have the little board and the code I used to boot the thing under DOS 2.0.
 
Hi guys,
Does anyone know if "TMS4116-25NL" will work on the 5150? If not I'll throw up a wanted thread!
Also does anyone know where I can get a SOTA 286 card driver? Google seems to not give anything.. Came in an XT I got recently... (hard drive has bad sectors)
 
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