IBM5150 rev 2

I have been working on the 5150 that I just recently got as a gift from another member of the forums. The person who gave me the PC installed an XT-CF lite rev 4. The computer booted fine with a cage board installed, but according to this thread http://www.vintage-computer.com/vcforum/showthread.php?3567-IBM-PC-5150-and-IBM-PC-XT-5160-FAQ, the rev 2 PC won't accept a VGA video controller, nor will it read anything more than 544 Mb of RAM. However, I was also told by other members here that there shouldn't be any problem installing these upgrades.

The thread also states that the BIOS won't allow any add on cards with their own BIOS extension. Yet the PC DOES BOOT FROM THE XT-CF lite.

Can you either confirm, or deny these claims, and provide a possible work around?

Any "Revision B" 5150 should be fitted with the third release of the BIOS (which is dated 1982).

If you had a Revision A, you probably wouldn't want 640KB and VGA anyway (and the work around would be simply to upgrade the BIOS to the third release).

bettablue said:

Can you either confirm, or deny these claims, and provide a possible work around?

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It sounds like you are confusing the motherboard versions (revisions) with the BIOS versions (revisions).

Early 5150s

* 16KB-64KB motherboard
* Motherboard supplied with the first revision BIOS, 04/24/81, and then later, supplied with the second revision BIOS, 10/19/81
* Both BIOS' have a 544 KB RAM limitation (not a bug), and do not support BIOS expansion ROMs
* Some people call these machines, 'model A'
* AST calls these machines, 'PC-1'
* Tecmar calls these machines, 'PC'
* The motherboard BIOS was commonly upgraded to the third revision

Later 5150s

* 64KB-156KB motherboard
* Motherboard supplied with the third revision BIOS, 10/27/82. It removes the 544 KB limitation, and supports BIOS expansion ROMs.
* Some people call these machines, 'model B', presumably because of the large 'B' (within a circle) stamped on the rear
* AST calls these machines, 'PC-2'
* Tecmar calls these machines, 'PC2'

modem7 said:

It sounds like you are confusing the motherboard versions (revisions) with the BIOS versions (revisions).

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Thanks for the quick response modem7. As always, I look forward to hearing from you.

I do believe you are correct in your assumption. The gentleman who gave me the computer did state that the PC is a revision 2 system, so I assumed (yeah, I know) that also meant the BIOS. Now though, when I look at the mother board, I clearly see 64-256 KB and right after that it has stamped "CPU" So to sort of answer my own questions; a 284KB memory upgrade can be installed to maximize the systems RAM to 640 Kb full potential, and the PC will also accept the EGA controller with RCA video output. If this info is correct, I'll try to complete the PC's configuration today, and possibly even get it connected to the TV/Monitor which is stored in the spare room.

I honestly can't wait to see how the computer boots with the XT-CF Lite installed; especially if I can use the CF card to bring files and other data in from my primary Windows PC. I may not need a tweener if this works the way I hope.

Thanks again.

bettablue said:

So to sort of answer my own questions; a 284KB memory upgrade can be installed to maximize the systems RAM to 640 Kb full potential, and the PC will also accept the EGA controller with RCA video output. If this info is correct, I'll try to complete the PC's configuration today, and possibly even get it connected to the TV/Monitor which is stored in the spare room.

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384K, not 284K.

IIRC a CGA card has an RCA video port but an EGA doesn't. It (the EGA) might have RCA jacks (two of them) but neither of them is composite video. They are feature connectors.

If you need to upgrade the ROMs to allow VGA and hard drives you might be better off selling the earlier version 5150 and getting a later model which would be cheaper.

I thought the ega RCA connectors were for composite video at first too. Did ibm even use that feature connector for anything?

It's not just IBM. I have a non-IBM EGA card and it has those useless connectors, too.

I actually needed two video controllers with a composite out option. I got one from hargle for only $10.00 shipped, and I have a deal in place with stone for the other. Why two? Because of limited space, I have two machines I need to connect to a single TV/Monitor I have just for that purpose. One of the computers is the 5150 PC I'm working on in this thread; the other is a 5160 XT. With both computers connected to the TV/Monitor, simply switching the input will display one or the other of the computers video signal.

From what I gather by reading the responses in this thread, the 5150 should accept both the 384 Kb RAM upgrade (thanks for the correction stone) and the EGA video controller. After I'm done with another issue happening today and tomorrow, I'll get into the dip switches and go for their configuration. Hopefully I'll be able to finish configuring the 5150 by the end of the week.

As I've previously mentioned, the 5150 PC did successfully boot to the CT-CF Lite, before it was shipped to me. So if it worked then, with it's included BIOS, then it should also work after I make the changes in the DIP switch settings. However, I then read the original IBM 5150/5160 FAQ thread, and that's where I got myself confused. Thanks everyone for helping to clarify what I was reading. I'll let you all know how it goes.

Thanks again... ~BB~

What happened to your other 5150?

Anyway, instead of composite video and a TV, I wonder if you could just use the CGA output on the cards you have and use one of those old serial selector switchboxes as a sort of KVM..except without the K and M of course. WOuld provide better video quality.

offensive_Jerk said:

What happened to your other 5150?

Anyway, instead of composite video and a TV, I wonder if you could just use the CGA output on the cards you have and use one of those old serial selector switchboxes as a sort of KVM..except without the K and M of course. WOuld provide better video quality.

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Howdy OJ.

To answer your first question, Alice, my first 5150 is pleasantly sitting on my left, next to my main computer desk. Because of new full height Control Data 30 MB hard discs, the expansion unit is working perfectly once again. DOS is installed, and the entire system is ready to do my bidding.

As far as getting another 5153 monitor, I'm afraid that's currently not in my budget. Living on a fixed income (Social Security Disability benefits) doesn't leave me with any money left over at the end of the month. That may change in June though. The TV/Monitor is already here too, so I'm using what I have available to me, at the cheapest way possible until I can start adding funds to me spending account.

I like your idea though. Alice has a 5153 monitor too, but I promised myself that I would never start taking ANYTHING from one computer to work on, or test another; not even a monitor. Once you start, you've set a precedent, and invariably other parts will find their way into other machines. At least that's my logic. I just don't want to start and end up having the best of one system all spread out in other setups. So, by using the TV/Monitor that I already have, the picture may not be as clean, but I know where all of Alice's upgrades, and system peripherals are.

I hope that makes sense. Thanks for your advice though. Trust me, I may not follow everyone's ideas, but I value them all the same.

bettablue said:

...but I promised myself that I would never start taking ANYTHING from one computer to work on, or test another; not even a monitor. Once you start, you've set a precedent, and invariably other parts will find their way into other machines..

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yeah, as someone who refurbishes, i dig what you say, thomas. i may steal an external device from another system for a moment on a quick test, but not much more than that.
i have lots of time to wait for other solutions and plenty of other things to do while i wait. my responsibilities will lighten this summer. woohoo!

luvit said:

yeah, as someone who refurbishes, i dig what you say, thomas. i may steal an external device from another system for a moment on a quick test, but not much more than that.
i have lots of time to wait for other solutions and plenty of other things to do while i wait. my responsibilities will lighten this summer. woohoo!

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I hear ya luvit. In my four plus years of collecting, repairing, and refurbishing vintage computers, I've heard of too many system units being scavenged for one part or other. Now the systems owner can't remember which computer got what, and he doesn't have that kick-a _ _ setup he had before he started moving parts around. He also now wishes he had never started that precedent. He told me that once he started, he had to keep going, and the computer system he had put so much time and effort in is no longer nearly what it was before he started. One of his biggest regrets was his decision to move his monitor to a different computer. Somewhere between systems, he tripped over his cat, and dropped the monitor. Luckily it didn't land on the cat, but the yoke was broken inside the case. The case didn't show any signs of damage though. He ended up taking it to a TV repair shop in North Las Vegas to have a new picture tube installed. Now at least his monitor is working as it should, but his overall system is missing some key upgrades he waited so patiently for.

I'm glad I'm not the only one who feels as I do. I'll keep looking for a deal on another IBM monitor to connect to both my new 5150, and the XT. I can easily disconnect it from one and reconnect it to the other within about a minute, so one monitor will work out just fine for now.

Anyway luvit... Thanks for your reply.

Take care.