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IBM 5150 early (16KB CPU) vs later (64KB CPU) versions

L

Lorne

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There is stuff all over this forum regarding the differences between early and later model IBM 5150’s, and I’m sick of going all over the place looking for it.

I’ve started this thread in the hopes of getting it all into one place.
I want to get pictures and descriptions of what the differences are, all in one place, and as you’ll see below, I’ve got some of them covered.

The part I’m having problems with, is the floppy drives but I want to know about the other differences as well.

Modem7 says he has an early 5150 but “it has a second edition ROM (U33=5700671)”.
I’m not sure what that means.

He also says: "the xt guy" on these forums has a 5150 with a first edition ROM. On his unit, "the date on the inside of the front cover is 01-82". I find nothing that looks like a date in the case of my unit.
I can’t find a date on the inside of my early (1.00 ROMs) front cover eiither.

The later version 5150’s had a build date tag on the speaker wires. Mine doesn’t have that. Was that only attached on the later versions?

The early versions also had a hole in the case under the power supply, which the later versions didn’t seem to have.

Another question is whether the disk drives had IBM logos on the drives or not.
Does anyone have a photo (of decent resolution) issued at the time of the 5150 release, that might give some indication as to whether the drives had logos or not?
I’ve heard that the very first 5150’s didn’t have the logo drives because of supply problems, but then I’ve also heard the opposite.

Could all those who have experience and knowledge with these early 5150’s please chime in?

Once I’ve got all the comments, I’ll post a reply summarizing all the info (with photos as applicable), so we’ll have it all in one place.

Thanks,

Lorne

Here's what I've got so far for identifiers on the IBM 5150 PC (16KB-64KB CPU)
(IBM 5150 PC (64KB - 256KB CPU) - photos on next post)

16KB-64KB CPU PC identifiers_Page_1.jpg
16KB-64KB CPU PC identifiers_Page_2.jpg
16KB-64KB CPU PC identifiers_Page_3.jpg
 
Also, the oldest expansion cards (floppy controller, video board, etc.) have a wide backplate painted black. These will not fit into an XT because the bracket is too wide (designed to fit the 5-slot PC spacing, vs. the narrower 8-slot XT spacing). Upon the introducting of the XT in 1983, IBM made the backplates narrower and unpainted (silver color).
 
Not all later model 5150's has AMD CPU's I have a photo of a 64-256K with an Intel CPU.

Modems 5150 must have the BIOS Upgrade kit, I have that also.

Here are some high-res photo's from the press kit, I don't see any logos on the drives. http://www.ibm5150pc.com/pcimg.zip

I don't to much about the date tags but all later models seem to have them, the floppy drives will give you a hint to your build time if thay have not been changed.




Lorne said:
There is stuff all over this forum regarding the differences between early and later model IBM 5150’s, and I’m sick of going all over the place looking for it.

I’ve started this thread in the hopes of getting it all into one place.
I want to get pictures and descriptions of what the differences are, all in one place, and as you’ll see below, I’ve got some of them covered.

The part I’m having problems with, is the floppy drives but I want to know about the other differences as well.

Modem7 says he has an early 5150 but “it has a second edition ROM (U33=5700671)”.
I’m not sure what that means.

He also says: "the xt guy" on these forums has a 5150 with a first edition ROM. On his unit, "the date on the inside of the front cover is 01-82". I find nothing that looks like a date in the case of my unit.
I can’t find a date on the inside of my early (1.00 ROMs) front cover eiither.

The later version 5150’s had a build date tag on the speaker wires. Mine doesn’t have that. Was that only attached on the later versions?

The early versions also had a hole in the case under the power supply, which the later versions didn’t seem to have.

Another question is whether the disk drives had IBM logos on the drives or not.
Does anyone have a photo (of decent resolution) issued at the time of the 5150 release, that might give some indication as to whether the drives had logos or not?
I’ve heard that the very first 5150’s didn’t have the logo drives because of supply problems, but then I’ve also heard the opposite.

Could all those who have experience and knowledge with these early 5150’s please chime in?

Once I’ve got all the comments, I’ll post a reply summarizing all the info (with photos as applicable), so we’ll have it all in one place.

Thanks,

Lorne

Here's what I've got so far for identifiers on the IBM 5150 PC (16KB-64KB CPU)
(IBM 5150 PC (64KB - 256KB CPU) - photos on next post)

View attachment 1424
View attachment 1425
View attachment 1426
Click to expand...
 
frozenfire75i said:
Not all later model 5150's has AMD CPU's I have a photo of a 64-256K with an Intel CPU.
Click to expand...
My newer 5150 was built in January 1986 and has an Intel 8088.

NEC was also a second-source used by IBM for 8088 chips. My dad's 5155 Portable PC had a NEC 8088 chip. This initially fooled me into thinking it was a V20, but it was just an 8088.
 
Lorne said:
I’ve heard that the very first 5150’s didn’t have the logo drives because of supply problems
Click to expand...
If that's me you're quoting, I was indicating that if discrepancies were seen, it might be because of supply problems.
For example, if at some time, an IBM manufacturing plant ran out of badged drives because of supply issues, that plant may have been forced to temporarily supply unbadged drives.
 
Introduction of the double sided drive

Introduction of the double sided drive

A discussion on the introduction of the double sided drive to the 5150:

The first BIOS for the 5150 (some call it "version 1.00 ROM") is dated 04/24/81 (part number 5700051).
The first 5150 Technical Reference contains the source code for that BIOS and the code shows support for both single and double sided drives. However the Hardware Overview section area of the first 5150 Technical Reference only describe drives that can store approx. 160 KB of data. That fits a known fact - the first 5150s had single sided drives.

Later, IBM released a second version of the BIOS on the 16/64K boards. It is dated 10/19/81 (part number 5700671), however it was probably at least a few months before it 'hit the streets'. This BIOS just fixed a couple of minor display bugs, which might explain why I've never seen a 5150 Technical Reference of about this time (maybe IBM didn't think it was justified for the small amount of code change).

IBM released a Technical Reference dated July '82. In the Hardware Overview section, it still speaks of diskettes holding 160KB of data, however, in a later part of the book, it has, "The drives are soft sectored, single or double sided". Interesting that even though a second BIOS had been released, this manual has the source code for the first BIOS.

EARLY '83

IBM produce a third BIOS, dated 10/27/82 (part number 1501476), which is seen on 64/256K motherboards. According to Scott Mueller, all 5150s sold after March '83 have the the third BIOS. IBM released a Technical Reference dated Jan '83, which has the source code for the third BIOS.


And so, reading that, I think we can safely say that the double sided drives were introduced sometime before July '82. And that fits in well with the release of PC DOS 1.1 in May '82, which compared to 1.0, supported double sided drives.

Now, was there a definite switch from single sided drives to double sided drives?

From page 11-12 of 'A Guide to IBM Personal Computers' (a document at http://www.ibm5150pc.com/docs.html), models 813/14/114/X14 had one single sided drive, and the model 824 had two single sided drives.

The first edition of Mueller's 'Upgrading & Repairing PCs' shows which 5150 models had which motherboards:
16/64K : models 1, 14,64, 74, 813, 824, X14, X64, X74
64/256K : models 104, 114, 164, 174, 166, 176, X66, X76

And so the model 114 had a 64/256K motherboard, and according to 'A Guide to IBM Personal Computers', came with a single sided drive. If that is fact, it means that IBM was supplying both double and single sided drives for at least six months (mid '82 to early '83).
 
Last edited:
modem7 said:
IBM produce a third BIOS, dated 10/27/82 (part number 1501476), which is seen on 64/256K motherboards. According to Scott Mueller, all 5150s sold after March '83 have the the third BIOS. IBM released a Technical Reference dated Jan '83, which has the source code for the third BIOS.
Click to expand...

Correct. The 64k-256k 5150 was introduced in March 1983 simultaneous with DOS 2.00.

modem7 said:
And so, reading that, I think we can safely say that the double sided drives were introduced sometime before July '82. And that fits in well with the release of PC DOS 1.1 in May '82, which compared to 1.0, supported double sided drives.
Click to expand...

The double-sided drives and second-revision BIOS 5150s were released at the same time as DOS 1.10 -- in the spring of 1982.

modem7 said:
Now, was there a definite switch from single sided drives to double sided drives?
Click to expand...

When the double-sided drives came out, they were optional. The SS drives were still available, and so was the cassette model of the 5150. Both of those were discontinued when DOS 2.00 was released.

The 64k-256k models were only available with DS drives. After 1983, the 5150 remained unchanged until it was retired in early 1987, the only new thing being the arrival of EGA in 1984. Unlike the XT, it never got half-height drives or support for 101-key keyboards and 3.5" floppies.
 
And, in 1983, even with a moderately good paying job, the 5150 was way out of reach as far as coming up with the price tag. I was still stuck with ONE 8" diskette drive because there was no way I could afford a second one. Ever try to copy CP/M diskette files to a backup floppy with only 32K of RAM and one drive. It can be done but painful is an understatement. Make one mistake and start over at the top. Of course, the files were larger than one cp/m directory entry could cover (one extent, they called it).
 
Fallo said:
The 64k-256k models were only available with DS drives.
Click to expand...
So that would either mean that Mueller is wrong about the model 114 having a 64/256K motherboard, or that 'A Guide to IBM Personal Computers' is wrong about the model 114 having a single sided drive.
 
Also sometime in 1983, IBM switched plants where thay made the 5150, all hand made/kit build 5150's will have a small barcode in the middle back of the chassie, all fully automatied buid 5150's will have the bar code to very right hand side of the system next to last slot!

http://www.ibm5150pc.com/mags/PC_mag_1982_boca_birth.zip That covers some info about the new vs old plant's!

In THINK magazine dated AUG 1983 It still show's photo's of the old plant http://www.ibm5150pc.com/mags/THINK.zip

So the switch was sometime after mid 1983.
 
You have to remember IBM had one year from the ideal on paper to it being in the hands of the public, so the 5150 was "not done" until early to mid 1981, so they I am sure we’re not worried about drives with logo’s, so later I would say they thought about it and order logoed drives, of course this toke time and I bet they did not order enough. I don’t know if early some early models had logoed drives and some did not, that would explain this!

modem7 said:
If that's me you're quoting, I was indicating that if discrepancies were seen, it might be because of supply problems.
For example, if at some time, an IBM manufacturing plant ran out of badged drives because of supply issues, that plant may have been forced to temporarily supply unbadged drives.
Click to expand...
 
IBMMuseum said:
That Intel 8088 (¨Copyright ´78¨) is the one with the interrupt bug...
Click to expand...

I don't much like the sound of that, especially seeing as that photo was of the chip on MY mobo.

Would we compare this to a little bug like a fruit fly, or a big bug like a grasshopper?
.
 
Lorne said:
I don't much like the sound of that, especially seeing as that photo was of the chip on MY mobo.

Would we compare this to a little bug like a fruit fly, or a big bug like a grasshopper?
.
Click to expand...

Small. Basically, if one executed a POP SS, the specification says that interrupts will be disabled for the following instruction. In the early chips, they weren't, so a POP SS/POP SP pair could have an interrupt hit between the instructions, causing some "interesting" results. I don't recall if the the same problem held for MOV SS,... MOV SP,... pairs or not.

At any rate, Intel notified its customers about it. The fix to code was simple--just disable interrupts before the POP SS and enable them after the load of SP.

Some of the folks who arrived on the scene after the bug was fixed may wonder at the seemingly unnecessary CLI/STI pairs. They weren't unnecessary.

Since Intel offered to replace offending chips free of charge, you probably have a collector's item there.

Early 286's also had a similar bug where doing a POPF with interrupts disabled where the IE flag being popped was also clear briefly enabled interrupts during the POPF.
 
Chuck(G) said:
Since Intel offered to replace offending chips free of charge, you probably have a collector's item there.
Click to expand...
My older PC (16/64KB motherboard, 10/19/81 BIOS) still has the original 1978-date 8088 chip. Strangely though, its A: drive and MDA board are from 1983, well after the introduction of the updated 1982 BIOS and 64/256KB motherboard. Perhaps those components were swapped in later. The B: drive appears original; it's a Tandon with no front panel IBM logo and has chip dates from 1981 and 1982. It is double-sided.

If you bought an 8087 from IBM, it came packaged with an 8088, and IBM said you had to install both at the same time. This was their way of helping to flush the buggy '78 8088 chips out of the user base. However, the IBM documentation mentions that some PCs had the 8088 chip soldered directly to the motherboard; in that case, IBM Service would replace your motherboard.

And yes, the fan in the original black power supply is much quieter than later versions. With no hard drive, the computer is nearly silent. I also noticed that "P8" and "P9" are handwritten on the motherboard power connectors in black magic marker, a neat little "human touch."
 
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