Upgrading the IBM PC/AT to MS-DOS 6.22 and Windows 3.1

 You read this correctly. What a software upgrade. My floppies for Windows/286 seem damaged. so...

Going from MS-DOS 5 to MS-DOS 6.22

Once I got the 1.44M floppy recognized, the 1.44MB MS-DOS 6.22 upgrade diskettes read correctly and the install process ran fine. DOS 6.22 takes up more memory but has some nice utilities and is the most state of the art version (to my knowledge).

It's a matter of feeding three floppies to upgrade. It's kinda touchy - it really wants things just right to upgrade the DOS and you cannot use the upgrade floppies for a new install (unless there is a trick I'm unaware of). It saves the old MS-DOS in a hard disk directory folder called OLD_DOS.1 in case you need things or decide to uninstall. Speaking of uninstall, all the MS-DOS upgrades want "Uninstall Floppies", usually one or maybe two to undo the upgrade. Just a PITA in my book.

Looking in my floppy collection, I found Windows/286. But the disks appear to be damaged.

I was wondering what to do so...

Installing Windows 3.1 on an IBM PC/AT

I have install 1.44MB 3.5" floppies for Windows 3.1 and Windows for Workgroups 3.11. If I remember correctly WfW wants an 80386. So I grabbed the Windows 3.1 diskettes. It talked about a mouse - lucky I got that ATI VGA Ultra card with in-port mouse built in. My 1080 VGA/DVI monitor did not like 640x400 mode so I borrowed the VGA LCD monitor from the Gateway Pentium III machine.

6 diskettes (119 files) later, I get the Windows 3.1 splash screen. 

The display is canted to the right. I want to adjust the screen resolution, if possible but I need to Google for that, my memory is not so clear on that and drivers doesn't seem to do display drivers to my knowledge.

Getting the IBM PC/AT to Recognize a 1.44MB Hard Disk

Lots of time this week getting my IBM PC/AT up to speed. Here's a synopsis:

Getting a New Compact Flash Hard Drive

Instead of the XT-IDE Compact Flash hard disk adapter, I switched it for a modern XT-IDE Rev 4 IDE controller card and an IDE to Compact Flash adapter. This way I can use a spinning IDE adapter or whatever later and use the old adapter in an XT machine. Much fiddling with jumpers and it worked. Same shenanigans getting it to be bootable. My latest trick is boot to DOS 3.1 then upgrade to DOS 5. That seems to work well. I now have a 128MB Compact Flash SSD working in the AT.

Getting the Sony 1.44MB 3.5 inch disk drive working

Even though my machine is the latest revision of the PC/AT made, with a BIOS dated 11/15/1985, the IBM Diagnostics Diskette (version 2.03) setup only has 360k, 1.2M and 720k floppy drive options. The BIOS does have code for 1.44M 3.5" drives. But how to set that? I went back to minuszerodegrees.net here and there is a third party program called GSETUP.EXE that can set the right drive type. Yay!

I just needed it on my Compact Flash hard drive. To do so, I used my Tweener Pentium III/500 to read the file off a thumb drive then write it to the Compact Flash card via a USB to Compact Flash card adapter. Yes, this is a lot of hardware for this type of work. I could have copied it to the Compact Flash from my modern desktop but I'm not that smart. It did allow me to copy GSETUP to my MS-DOS 5 boot floppy - likely why I chose that route.

With GSETUP.EXE, I ran it (no special boot required and indeed I could chose 1.44MB 3.5" drive as a choice for drive B. Then I could read and write high density 3.5" drives like I should. Yay!

See the next installment for upgrading DOS & more.

Getting a non-functional IBM PC/AT up and running is hard

 It's been a long time without posts. Maybe I can correct this.

A couple months ago, I took the plunge and got an IBM PC/AT. I've wanted one for almost 40 years. I have an IBM PC, two PC/XTs, and a 5160 portable. A 5170 is next in line ATs were very hard to get for the last couple years but units are showing up on eBay with various descriptions, usually untested. No keyboard, monitor, cables, etc. So one goes off a few pictures and hopes for the best.

Here is the one I got late 2022. I knew it had two floppies, some type of display card, a hard drive, a memory add-on card and two network cards. The seller threw in a non-IBM (cheapo) keyboard which was great. I got it on the bench and start to look. The Seagate ST-225 drive is unresponsive, it doesn't spin - a bad sign. It has a generic IBM Monochrome card, ok. I splurge for an ATI Ultra ISA VGA card with bus mouse off eBay. That'll allow me to use a VGA flat panel monitor.

I quickly learn that the PC/AT is not like the earlier IBMs. It keeps BIOS configuration information in CMOS rather than via motherboard jumpers. And this memory can only (mostly) be set via a special IBM 5.25" diagnostics floppy disk. If you have this problem, see this website on how to proceed. I got the disk image and took it to my Pentium III PC and wrote a disk. I did use a 1.2MB drive to write a 360K disk as my 360K drives were misbehaving. It worked, I could set parameters in the AT by booting the diagnostics disk.

I replace the BIOS memory back up battery (not corroded thank goodness) with an AA battery pack. All good. See this on the procedure.

With the diagnostics disk, I could finally boot, displaying on the monitor. I learned the AT is a model 339, 512KB memory onboard (not stacked DIP chips). Drive A works, floppy B doesn't (seek errors), and the hard drive is indeed dead.

Here are the add-in cards (besides the floppy/hard disk card not shown). From the top, an IBM monochrome adapter (plus serial/parallel), 10-base-T network card, Serial/parallel card, and an interesting IBM Token Ring network card. None immediately needed to debug/use the machine but I'm not complaining. 

I get an XT-IDE ISA to compact flash card and put in a 16MB CF card. I had issues with that until I used the XT CD-ROM in the Pentium III to mark the drive via FDISK /MBR. Then I could format the drive and I loaded PCDOS 2. I upgraded it via floppy to MS-DOS 5.0. There are a slew of XT-IDE cards out there and some don't play nice with the AT without clone ROMs which would be a huge headache. So I'm glad the one I have played ok.

Meanwhile, I didn't turn my alert off on eBay and another IBM PC/AT machine popped up at a good price. Amy bought it for me for a birthday present. It has parts that complement the PC above. I'll dive into that one in the next post.

Using EGA and VGA video cards in IBM 5150 PC, 5155 Portable, and 5160 PC/XT Machines

I first ran into video card issues debugging the IBM 5155 Portable computer. Besides no video it beeped one long, two short on startup. I did a lot of video card switch and jumper gymnastics to try to get that straight when I should have done more digging online. Two switches on the motherboard would have probably done the trick.

So I have compiled a short primer on using EGA and VGA displays on these machines. Most of the info is from various pages of the excellent minuszerodegrees.net site but in multiple places. Hopefully having this in one place helps others.

Do note: there are alot of caveats in this and not all cards will work in all computers. One reason I don't make a compatibility table (yet) is others have done so and it gets expensive testing.

Motherboard switch settings for EGA and VGA (BIOS-containing) Video Cards

Version 1.00

IBM 5150 PC

·       The IBM 5150's motherboard must have the third BIOS revision, 10/27/82, for EGA/VGA

o   The ROM has the IBM part number of "1501476" printed on it.

o   On the 5150 motherboard, the ROM in socket U33 contains the BIOS.

o   Due to bugs, this BIOS requires that all 4 banks of motherboard RAM be populated.

·       The two video switches on SW1 (shown below) must be set for:  5=ON, 6=ON

·       Of SW1 and SW2, SW1 is the switch block closest to the center of the motherboard.
These settings apply to both the '16KB-64KB' and '64KB-256KB' versions of the 5150 motherboard.

·       If your IBM 5150 contains an XT-class hard disk controller, then be aware that some VGA cards may have a resource conflict with it.

·       Known working VGA card lists: minuszerodegrees, vcf

IBM 5155 Portable PC

The IBM 5155 contains an early version of the IBM 5160 motherboard.

So, see below to see the 5160 motherboard switch settings, noting that the two switches for video card type are normally set to CGA (because an IBM CGA card is the card supplied by IBM in the 5155).

IBM 5160 PC/XT

·       The two video switches on SW1 (shown above) must be set for:  5=ON, 6=ON

·       Do not place the card in expansion slot 8 (the slot nearest the CPU) unless the card specifically supports slot 8.  Cards that are slot 8 compatible usually have a 'slot 8' jumper.

·       If your IBM 5160 contains an XT-class hard disk controller, then be aware that some VGA cards may have an address space resource conflict with it.

·       Known working VGA card lists: minuszerodegrees, vcf

Boot Error Beep Codes for Video

1 long and 2 short beeps                    Video (Mono/CGA display circuitry) issue

1 long and 3 short beeps.                   Video (EGA) display circuitry

1 beep, blank or incorrect display       Video display circuitry.

·       Make sure the SW1 switches are in the correct 5=ON 6=ON position (above)

·       Ensure there are no conflicts between VGA BIOS/addresses and other cards

·       Be sure the video card configuration switches are correct (this could be hard without documentation)

Suitable VGA cards

•	You must not assume that because a particular VGA card works in an IBM 5160 (IBM XT) that the same card will also work in an IBM 5150.
•	The documentation for some 16-bit VGA cards indicates that they work in an 8-bit expansion slot.  You should not expect that to mean all 8-bit slots.  Many such cards are intended only for an 8-bit slot within an AT-class computer, and will not work in an IBM 5150.  The maker's documentation for the card will indicate whether the card will work in an IBM 5150.
•	Some people have discovered that certain 8-bit compatible 16-bit VGA cards can be made to work in a 5150/5160 if the 8088 CPU on the motherboard is upgraded to a V20 CPU. This may not work, though.

VGA card configuration

•	Some VGA cards have configuration switches and/or jumpers.  An example is here.  Refer to the card's documentation to ensure that those switches/jumpers are set appropriately.  For the switches, do not confuse the off position with the on position.
•	16-bit VGA cards that are known to work in an IBM 5150 PC usually (not always) need to be manually configured to run in 8-bit mode.  Refer to the card's documentation, because configuration is done differently on different cards.

Documentation for the Paradise Systems MGC II 8-bit MGA/CGA/Composite Video Card

In the 4th IBM PC I purchased, an IBM PC/XT 5160, the video card that was in the system was the original card bought around May 1986. Fortunately I also had the IBM binders from the PC and the documentation was in the system binder.

This is the Paradise MGC II video card version 4.0. Full length, it can display Monochrome Graphics Adapter, Color Graphics Adapter, or Composite video out (selectable via jumper). 

The card was built to be modular so daughterboards such as a parallel printer adapter board could be added. The card I received had no daughterboards.

The documentation for this card is very scant on the Internet, with the only real documentation I found is at:

• Here - Bare configuration

The documentation hints that Paradise may have been affiliated with Western Digital. Wikipedia bears this out without reference:

• Paradise Systems - acquired by Western Digital, later sold off to Philips

If anyone knows of decent documentation for Paradise gear, please let the Internet know including me at @mikedigitalhome on Twitter.

Scanned Documentation

Here is a PDF of the material I have: pictures, disk, warranty card, quick sheet, and manual

Paradise Systems MGC II Video Card Documentation (PDF)

IBM Portable PC 5155 Video Connection

Since buying one IBM PC, I have now progressed to buying 4: 1 PC 5150, 2 PC/XT 5160, and an IBM Portable 5155. Two types of COMPAQ portables are on the way. Help!

Here I will focus on the IBM Portable PC Model 5155. I bought this off of Craigslist from a gentleman who found it in a thrift shop. It was a bit rough, video was there but only tearing lines, the brightness know is missing and one keyboard retention foot is broken.

Get the manual

I suggest you go to this page to get a copy of the maintenance manual for this computer:
https://ibm.retropc.se/hmr/hmr.html 

Opening the IBM 5155 Computer Case

Opening up the PC, you remove 6 screws located around the front of the PC looking at the CRT and disk drives. Pull the case off. Remove the internal RF shield on the PC half via 3 screws around the shield. Bag the screws for safe keeping.

My Experience - ugh!

The short of it: Try to use a CGA card, preferably an IBM CGA card or close compatible.

I looked around the video card. There was a loose twisted pair of wires. Black and Yellow on a 4 pin header. Some Googling found this was composite input to the video section, yes we found why there was no text on the display!

The video card inside was an Everex EV659. Interesting as this is billed as CGA/MDA/EGA compatible. Like many vintage hardware pieces/cards, the online documentation is pretty sketchy.

But for the life of me I could not get composite video out of the header pins.

Maybe it's this bad 2.2uf tantalum capacitor next to the header? Time to get some more capacitors from Digi-key!

At this point I decided to use the Everex card in another PC. It's flexibility is better suited to a desktop. So I grabbed a known good CGA adapter, the CGA clone I documented in this earlier post.

The composite out didn't correspond to the IBM CGA header. Nearly all the early IBM compatible 8-bit hards have a 4 pin header for composite video out, which may be marked RF adapter as that would be how an RF modulator would connect so a OC could display to a TV of the time without composite in. I know of no one that actually used a TV, they got a mono monitor and used that if an IBM monitor was too expensive (it often was).

I did confirm with a CGA monitor that the portable booted correctly (with a DOS Boot Disk). So the PC is ok.

Connecting the IBM Portable 5155 to a display card

Determine the composite video out of your display card. For the official IBM CGA card, here is the manul picture:

So the Yellow wire (Composite In) should in theory go to CGA P1 Pin 3 and the Black wire (Ground) should go to P1 Pin 4.

The picture on minusZerodegrees.net shows this same connection for a CGA card.

If you do not use an official IBM CGA card, the connections and picture may not be correct! As it turns out, my clone CGA card apparently has the header upside down from the official card!

I used male to female jumper wires as the connection is very tight and the clone card has 4 pins where the connector has pin 3 keyed (Pin 2 missing) so the 5155 video in cable doesn't fit.

Using non-official CGA or other cards

The card you plan to use should have a good video composite out and ground. Many cards have RCA jacks out the back that provide this, but it is awkward and unsightly to have a connector to the jack snake back in to connect to the display's Yellow and Black connection.

I suggest if you are probing your video card for composite out to use an external monitor (if you have a composite monitor) so you don't accidentally put that +12V line onto your 5155 video in, as it might damage it. I have a small LCD composite monitor I found dumpster diving but composite monitors can be found in other places, including old TVs with composite in. Maybe even an old VCR with video inputs and a better system for output.

Can I get VGA on the display (I don't think so)

If you were thinking of going up to VGA, note that there are a limited number of vintage VGA cards that work with 8 bit IBM PCs. See this list for some known to work. Also such cards probably don't have video out or at least one that will work better than CGA. CGA was designed for regular NTSC or PAL composite monitors of the era. VGA was designed for specialty monitors.

Perhaps you could replace the video section with something that will display VGA (or better). This would be a non-vintage mod but it sounds interesting!

Conclusion

I'm glad the video section was ok as I am not a tube video expert by any means. I like the portable format, they were the first IBM PCs I actually used for school work. I even wrote Unix clone programs like for mv, ls, etc.

If you have more info on the IBM Portable 5155 beyond the excellent documentation at minuszerodegrees.net, please share.

Bonus: If you see the display pictures at the top, what is strange about that directory list? Let me know on Twitter @mikedigitalhome

The IBM PC 5150: Part 7 - The Hard Disk Controller

Continuing from part 6 of my teardown of a one owner IBM PC 5150 from the 1980s.

Here is the controller card supporting a half-sized hard drive. I haven't gotten down to the hard drive label but I have a suspicion it's an RLL 30MB unit (given RLL added 50% to a 20MB drive). Let's look at the card controlling it:

The left side reads DATA TECH 5160 X. Assembly REV D.

There is an installation guide on minuszerodegrees.net! It doesn't say what Rev D is but for Rev C,  10-05-88, BIOS address jumpers so this must post-date 10/1988 meaning this was a later add-on and this is supported by the fact I was given the original full height floppy where the half-height hard drive and floppy now live.

With a google we have stason.org's documentation:

DATA TECHNOLOGY CORPORATION

DTC5150X, DTC5160X

Data bus: 8-bit, ISA.
Size: Half-length, full-height card.
Hard drives supported: DTC5150X:Two MFM ST506/412 drives
DTC5160X:Two RLL ST506/412 drives
Floppy drives supported: None

And the diagram is similar to below except W3 (1 position) is an unpopulated 8 position in my board:

CONNECTIONS
Function	Location
34-pin control cable connector-hard drive	J1
20-pin data cable connector-drive 0	J2
20-pin data cable connector-drive 1	J3
4-pin connector-drive active LED	J5

USER CONFIGURABLE SETTINGS
Function		Location	Setting
»	615 cylinders, 4 heads	W3 (5150x only)	closed
	BIOS drive type selected at low-level (see table below)	W3 (5150x only)	open
»	Factory configured - do not alter	W2/jumper 4	open

BIOS ADDRESS
Address	W2/jumper 1	W2/jumper 2	W2/jumper 3
disabled	open	-	-
C8000	closed	closed	closed
CA000	closed	closed	open
D8000	closed	open	closed
F4000	closed	open	open

So let's go to the card:

Connectors: J1 and J2 have cables for a drive 0 (C: in DOS). J2 is empty as there is only one drive. The drive activity header J5 is unconnected, the install guide says this is for AT hard drives. And there is no further information on connecting to that header.

For Block W2, there are only pins on positions 2, 3, and 4, and they are all closed. This puts the hard drive BIOS address at C800:0000.

Drive Type Table

The types of drives supported is hard coded into the card BIOS. Fortunately later BIOSes had a free form type. Here is the table from the install guide:

I'll backfill what type of hard drive is found.

Hard Drive Controller BIOS Chip

The BIOS chip agrees with the documentation as a 5160X, having a CRD prefix. This would be BIOS rev 19A.

REVISION HISTORY: DTC5160x

Rev. Date Description

A 06-17-88 Initial release
B 08-08-88 AT LED connector
C 10-05-88 BIOS address jumpers
D 01-10-89 CXD23A BIOS

The board rev is D but the value doesn't match CXD23A. It may be a rev C BIOS.

Finally, the documentation says:

This controller has a built-in, low-level format program. To enter the program run the DEBUG utility supplied with DOS and at the prompt enter: G=C800:5.

Which is helpful as if the drive needs to be initialize, that information is needed.

PC BIOS Support

Via minuszerodegrees.net:

Early 1983, some significant events occurred.  The IBM 5160 (IBM XT) and DOS 2.0 were released, and they supported hard drives.  The BIOS on the 5160 motherboard introduced support for BIOS expansion ROMs, and so now it was possible for a hard drive controller card to have its supporting BIOS located within a ROM on the card.

About this time is when a new revision of motherboard BIOS appeared for the IBM 5150, the 10/27/82 revision, and it too had support for BIOS expansion ROMs.

So at this time, someone with a 10/27/82 BIOS equipped IBM 5150 could fit an XT-class hard disk controller, a hard drive, and run DOS 2 - all that would need to be worried about was whether or not the 5150's 63W power supply was going to be adequate for the task.  But at the time, it was not adequate (due to the power requirements of current hard drives).  It is the reason why IBM put a 130W power supply in the 5160.  The diagram at here shows that the +12V start-up power requirement of the Seagate ST-412 easily exceeds the +12V power rating (24W) of the 5150's 63W power supply.

At this time is when IBM offered a hard drive solution for the IBM 5150.  It was the attachment of an IBM 5161 expansion unit (one that contained a hard drive and controller) to the 5150.


POST 1983

Hard drives became physically smaller, and their power requirements smaller.  Therefore, the 5150's 63W power supply becomes less of an issue.  For example, it is reported that a Seagate ST-225 works okay with the 63W power supply.

It appears the PC has a replacement 125 watt power supply, still uncertain though. I would think the vintage is older than 10/1982 so it should have a compatible BIOS and work with DOS 2 or higher. Having seen this PC in operation under DOS 4, things seem ok.

I still need to determine the BIOS date, I'll need to reassemble and reboot I think. The chips I believe are the BIOS have a big 17 on them and a smaller 20.

Final Thoughts

Having a hard drive was a BIG THING in the 1980s, at least for a home computer. It was a popular add-on for PC owners looking at their AT-owning friends. I myself got a 30MB RLL drive for my Compaq DeskPro as an add-on, like this computer. Boot times improved and oh, the storage, no floppy swapping. Who could ever fill a 30MB drive? There were no MP3s, videos, etc.