IBM PC XT 5160 - Early version

[Tyler Durden]

I have an IBM 5160 that has a BIOS ROM U18 with IBM part number 500026. The ROM is a ceramic package with a gold lid.

The motherboard is also slighly different than the two shown here:
http://www.minuszerodegrees.net/5160/motherboard/5160_motherboard_revisions.htm

Mine has an Intel 8088.

It also has the number 4073 stamped to the right of the silkscreen "64 - 256KB SYSTEM BOARD"


I read that nobody has seen one of these motherboards in the wild and have not seen this BIOS PROM.

Is this system one of the first XT's?

 

[modem7]

The motherboard is also slighly different than the two shown here:
http://www.minuszerodegrees.net/5160/motherboard/5160_motherboard_revisions.htm

If people were to include factors such as: PCB colour, makers of certain chips, colour of capacitors, labelling, PROM versus EPROM, ROM revision, wiring modifications, slight differences in trace positioning, etc., it could be that there are, at the low level, 30 or more motherboard revisions.

And perhaps IBM kept track of that internally, but if you look at IBM's user documentation, there are only two 5160 motherboard revisions: 64-256KB and 256-640KB. The web page you pointed to (I am the author) reflects those two 5160 motherboard revisions: 64-256KB and 256-640KB. The photos are simply representative of what can be found.

I have an IBM 5160 that has a BIOS ROM U18 with IBM part number 500026 ...

There is information on the 5000026 chip in the first post of the thread at [here].

I read that nobody has seen one of these motherboards in the wild and have not seen this BIOS PROM.

Whomever wrote what you read cannot possibly prove that. For example, did they track down and ask everyone who has ever opened up an XT (since the time that the XT was released). And it is possible that if we were to now, go and examine all of the surviving 5160s in the world, that more examples of the 5000026 chip will be found. It's just a big unknown.

But your 5000026 chip is the first that I have heard of. I now have to seriously think about modifying the web page at [here].

Thanks for letting us know. Any chance of a photo (in focus), like the one at [here] ?

Is this system one of the first XT's?

I think that all we can say is that it must be an early one.

In my opinion, there is a question as to whether or not IBM released 5000026 based 5160s. I have not seen convincing evidence either way. For all we know, your 5160 had been stored in an IBM vault, and one day, an employee ended up taking it home. Or conversely, perhaps a few hundred were produced and sold, and you have one of the few remaining.

 

[Tyler Durden]

Pictures

Pictures

Here are some pictures.

Il also upload some pictures of the installed cards. It is curious that the serial card, "black and white" card, and the floppy drive have wires on them. For large production they probably respun these PCBs, integrating these fixes...

 

[Tyler Durden]

More pics

More pics

Here are some more pictures

 

[Tyler Durden]

500026 bios

500026 bios

Tried to post pictures but was unsuccessful. Trying again.

View attachment 24822View attachment 24822

 

[modem7]

Here are some pictures.

Thanks.

If the 5000026 chip is original to the motherboard, and the motherboard original to the case, then by the case serial number, we can hypothesize that at least the first 6,000 XTs had the 5000026 chip. Speculation.

It is curious that the serial card, "black and white" card, and the floppy drive have wires on them. For large production they probably respun these PCBs, integrating these fixes...

I have been a member of these forums since 2006, and consequently, seen lot of photos of IBM 5150/5160/5170 motherboards and cards that were posted by other members.
Hookup wire on such motherboards/cards is certainly not rare, with yellow coloured wire being by far, the most common colour.

I have sometimes wondered which was the case:
1. IBM mandated the use of yellow coloured hookup wire for the PC range; or
2. To save money, IBM's supply department bought one gigantic bulk purchase of hookup wire (yellow coloured).

 

[Malc]

Out of interest is there a date code on the inside of the top cover and the inside bottom of the case ?

 

[Tyler Durden]

The underside of the chassis has a serial number stamped into it which is the same as the serial numebr on the rear barcode sticker. My other XT's do not have have a serial number stamped on their bottoms.

Interesting also is that the serial number barcode sticker is on the left side of the chassis rather than on the right. I believe this machine is an IBM prototype or a beta machine for these reasons:

- 5000026 BIOS ROM
- chassis stamped
- serial number sticker located on the left side rather than on the right.
- power supply is unusual. it has an IBM part number, but also the name Astec.
- disk drive has wires on it.
- "black and white - parallel" video card has wires on it.
- serial card has wires on it.

I dont think IBM would have shipped (in volume) a system with so many components with wires on them, so this machine is probably some kind of beta machine, or as was previosuly suggested, an IBM-internal "vault" machine that some employee may have taken home.

Anyway, it is an interesting machine. I already have a few upgraded XT's, so I think I will list this one on ebay.

Thanks

 

[Tyler Durden]

PS: This motherboard also does not have the silkscreen "No Copying Permitted" betweeen the ISA bus slots. All 5160 motherboards I hae seen so far have this intimidating warning on them...

 

[per]

I have a very early XT as well, serial number 0010472 and assembled 23 February 1983. It does have the same motherboard, and with the number 1501490 on the back of the PCB. The same number was stamped between the expansion slots, but stamped over and replaced with a 1501655 stamp. The BIOS, however, uses the 1501512 in the same cheramic package as yours 5000026, and datecoded only a single week after.

When it comes to motherboard revisions, there were actually very few physical changes. The only signifficant difference between 64k-256k and 256k-640k boards were in the configuration. Maybe the 256K-640K boards lost the posibility of using 8K ROMs for BIOS, but that would be the only "real" difference in the case. On that note, though, there were a more signifficant update to the motherboard in early 1984, relating to some DMA timing ajustments (some early boards have been upgraded using a chip in "Spare" and a whole lot of patch-wires). Second revision 64K-256K boards after this update has an U90 instead of the "Spare" location.

I allways wondered why the old board product number was stamped over, but I think the BIOS update may be related to it.

 

[gslick]

If you're lucky it will be worth as much to someone as a prototype Commodore 264. Guess we'll find out.

http://www.ebay.com/itm/151804412825

 

[per]

What would be very interesting is to find out what date is stamped in the back of the front cover of this machine. From that we can get a slight indication of how fast the first production XTs were assembled, but also in what order things got sorted out.

What is intriguing is to see that the 5000026 is datecoded 4th week of 1983, while my 1501512 is datecoded 5th week of 1983. That's a really small difference, and this can only mean that they changed to producing the new BIOS in the end of January 1983. I will guess they used the 5000026 in the earliest of the early machines to save production time.

If my assumption that the restamping of the motherboard product number in my machine indicates the newer BIOS, then it (and all first-run XTs) must have been intended to have the 5000026 initially. Depending on when your machine was assembled, it might have been put together before BIOS chips were produced at all, and the secondary BIOS chips might have been installed as soon as they arrived from factory.

As my machine has serial number 0010472, it's pretty safe to assume that between 5000 and 10000 of the first XTs came with the 5000026. Now, the thing is that your machine and mine are the only two first-run XTs I have ever seen so any first-run XT is a pretty rare sight.

PS. there were patch-wires on expansion-cards in my machine as well, so yes IBM did actually ship computers with these sort of fixes.

 

[xupista]

Tyler: We need a dump of your 500026 ROM chip so the MAME team can confirm or refute whether their contents match.

 

[fs5500]

I think IBM PC XT 5160 Early version with 5000026 BIOS seems to be very rare than IBM PC 5150 Early version with 5700051.

The following onwers seen to have IBM PC XT 5160 Early version on vcfed.
(L/N -- Lot No. , P/N -- Part No. , S/N -- Serial No.)


1)Motherboard with 5000026 BIOS (P/N : 1501491)

*fs5500 (2ea - L/N : 1612, L/N : 3023) -- All L/N of BIOS chips are 8251 (S/N on 5160 case : ??????? , I don't have IBM PC 5160 case)
*MicroCoreLabs (1ea - L/N : ????) -- L/N of BIOS chip is 8304 (S/N on 5160 case : ????????)
*Tyler Durden (1ea - L/N : 4073) -- L/N of BIOS chip is 8304 (S/N on 5160 case : 0005886)


2)Motherboard with 1501512 BIOS (P/N : 1501490)

*per (1ea - L/N : 4103) -- L/N of BIOS chip is 8305 (S/N on 5160 case : 0010472)

 

[modem7]

1)Motherboard with 5000026 BIOS (P/N : 1501491)

*fs5500 (2ea - L/N : 1612, L/N : 3023) -- All L/N of BIOS chips are 8251 (S/N on 5160 case : ??????? , I don't have IBM PC 5160 case)
*MicroCoreLabs (1ea - L/N : ????) -- L/N of BIOS chip is 8304 (S/N on 5160 case : ????????)
*Tyler Durden (1ea - L/N : 4073) -- L/N of BIOS chip is 8304 (S/N on 5160 case : 0005886)

When member MicroCoreLabs posted photos of his set, I noticed that his set (both the 5000026 and 5000027 chips) had markings/scratches that matched with Tyler's set. It was particularly noticeable for the 5000027 chip - see [here]. When I then queried MicroCoreLabs, he agreed that his set was the same.

BTW. If you email to me, a photo of your second 5000026/5000027 set, I will add it to [here].

 

[fs5500]

@modem7

Sure.

https://mega.nz/#!S01yUKpI!hRLtOolcbuj5CdjQ1TyGcKiNMUFKESejXRHOrHFteQQ

Total size is 267MB.

I fixed the information.

1)Motherboard with 5000026 BIOS (P/N : 1501491)

*fs5500 (2ea - L/N : 1512, L/N : 3023) -- All L/N of BIOS chips are 8251 (S/N on 5160 case : ??????? , I don't have IBM PC 5160 case)
*Tyler Durden (MicroCoreLabs) (1ea - L/N : 4073) -- L/N of BIOS chip is 8304 (S/N on 5160 case : 0005886)


2)Motherboard with 1501512 BIOS (P/N : 1501490)

*per (1ea - L/N : 4103) -- L/N of BIOS chip is 8305 (S/N on 5160 case : 0010472)

 

[fs5500]

IBM PC XT 5160 BIOS (Part No. 1501512) is listed on eBay.

https://www.ebay.com/itm/IBM-Intel-...rtment-1980-1981-1982/174241922900?nordt=true

I figured out that IBM PC XT 5160 BIOS (P/N. 1501512) was made from Jan.1983.