IBM 5140 PC Convertible Questions

[motley2659]

Hey guys,

I am the winner of this sweet IBM 5140 lot on ebay

http://www.ebay.com/itm/IBM-039-s-FIRST-Laptop-Computer-Vintage-Convertible-PC-5140-model-2-Plus-Extras-/251569962555?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2047675.l2557&nma=true&si=mVE1D%252B4lfzYyhajmgqRY7FMoftk%253D&orig_cvip=true&rt=nc

and I have a few questions that I haven't found answers in my research:



1) Are the ports on the serial/parallel slice bidirectional? If not, can they be modified like the PCjr?


2) The technical documentation states that the system has a Real Time Clock (RTC). Is this backed by a coin cell or the system's NiCad battery pack?


3) Is the 8088 processor on this thing socketed (like the PC/XT) so that it can be replaced with a NEC V20? If so, is there a list of programs and games made incompatible by this upgrade?


4) The system comes with IBM PC DOS 3.2. Is there any advantage for upgrading to PC DOS 5.0 on this machine?


Feel free to add any other suggestions or recommendations on software, upgrades, etc.

 

[motley2659]

Bump. Did I post this in the wrong forum?

 

[mbbrutman]

Bump. Did I post this in the wrong forum?

Please don't bump, but yes, I'm surprised that nobody else chipped in ..

[1] I've not looked at the parallel port implementation but I suspect that it is not discrete TTL logic like on the earlier machines. So your chances of doing a modification and pretty small.

[2] The NiCad battery pack is removable. There is probably a smaller, on board battery. It might not be a coin cell.

[3] It is a low power version of the 8088 or 8086 ... I can't remember. So it's not going to be pin compatible with a V20.

[4] DOS 5 really doesn't do anything for the machine, unless you need something specific that only DOS 5 has. Some device drivers might require it, but I can't think of any.


In a nutshell, it is not a terribly upgradeable machine. I still enjoy mine - you will notice that it is prominently featured at http://www.brutman.com/mTCP/ running an IRC client.


Mike

 

[Great Hierophant]

If you want better upgradeability, I would have recommended a Tandy 1400LT. You can put a hard drive in it, which might be able to take advantage of DOS 5.0. The floppy-drive only 5140 will see little benefit.

I have a question about the 5140, or more specifically its CRT adapter. Does the composite output artifact colors match the IBM CGA colors? Or are they very different like the IBM PCjr.'s artifact colors?

 

[motley2659]

[2] The NiCad battery pack is removable. There is probably a smaller, on board battery. It might not be a coin cell.

I looked at the technical manual and it doesn't show any evidence for a battery, nor is there any reference to a "back-up battery", "cmos battery", or "RTC battery" for this model under search. The reason I brought up the NiCad as backing up the RTC is because I used to own a Amstrad PPC 512 and the C cells backed up the RTC if the AC adapter was disconnected.

If you want better upgradeability, I would have recommended a Tandy 1400LT. You can put a hard drive in it, which might be able to take advantage of DOS 5.0. The floppy-drive only 5140 will see little benefit.

I have a question about the 5140, or more specifically its CRT adapter. Does the composite output artifact colors match the IBM CGA colors? Or are they very different like the IBM PCjr.'s artifact colors?

I picked IBM 5140 more for the aesthetics than performance. The auction that I won includes the CRT slice and I'm thinking about picking up an IBM 5144 Composite Monitor from eBay.

 

[Great Hierophant]

I picked IBM 5140 more for the aesthetics than performance. The auction that I won includes the CRT slice and I'm thinking about picking up an IBM 5144 Composite Monitor from eBay.

I hope you know that monitor is monochrome, green-only. For color, find a TV set or the 5145 digital RGB monitor.

 

[motley2659]

* @ mbbrutman After searching on Usenet, it looks like the RTC on on the IBM 5140 is backed up by the NiCad battery pack. There is no coin cell, or soldered battery on the motherboard. It's odd and irritating that all of the PC Convertible's documentation doesn't express this specifically.

* @ Great Hierophant, yes I know it's monochrome, but I plan on using it for word processing so I want a monitor that shows text clearly. In terms of your original comment on the way composite output matches CGA colors, from what I read the 5144 shows multiple shades of green. So when I play something like the the CGA composite version of Wasteland, it should display a more defined picture than just the RGB CGA version, even (or especially) in monochrome. Right?

* @ mbbrutman as far as the processor goes, you're correct about the CMOS version of the 8088, I should have known that that would not have been upgradeable.

* @ mbbrutman in further research it looks like PC DOS 5.0 will allow me to have drives that aren't limited to 32MB. The reason I bring this up is because, due to your post on your PCjr website, I plan on using one of those parallel CF card readers and I want to be able to access up to 2GB. Which brings me back to the question of whether the IBM 5140 Parallel/Serial slice is bidirectional, or will I be relegated to nibble mode? In that thread, you state that the transfer limit is 50kb/s, while a bidirectional parallel port should give me 150kb/s-250kb/s. Right?

 

[mbbrutman]

* @ mbbrutman After searching on Usenet, it looks like the RTC on on the IBM 5140 is backed up by the NiCad battery pack. There is no coin cell, or soldered battery on the motherboard. It's odd and irritating that all of the PC Convertible's documentation doesn't express this specifically.

* @ Great Hierophant, yes I know it's monochrome, but I plan on using it for word processing so I want a monitor that shows text clearly. In terms of your original comment on the way composite output matches CGA colors, from what I read the 5144 shows multiple shades of green. So when I play something like the the CGA composite version of Wasteland, it should display a more defined picture than just the RGB CGA version, even (or especially) in monochrome. Right?

* @ mbbrutman as far as the processor goes, you're correct about the CMOS version of the 8088, I should have known that that would not have been upgradeable.

* @ mbbrutman in further research it looks like PC DOS 5.0 will allow me to have drives that aren't limited to 32MB. The reason I bring this up is because, due to your post on your PCjr website, I plan on using one of those parallel CF card readers and I want to be able to access up to 2GB. Which brings me back to the question of whether the IBM 5140 Parallel/Serial slice is bidirectional, or will I be relegated to nibble mode? In that thread, you state that the transfer limit is 50kb/s, while a bidirectional parallel port should give me 150kb/s-250kb/s. Right?

What thread?

I don't think I have tested the speed of the parallel port on the IBM 5140. I don't think it is ever going to hit 150KB/sec though. It's a very slow machine (under 10Mhz.)

A standard serial port can write 8 bits at a time on the data lines and read 5 bits at a time on the control lines. So reading something from the port is effectively 1/2 the speed of writing something to the port. Bi-directional just means that the data lines can be used for both reads and writes; it is just going to make the reads as fast as the writes.

Another issue is that a lot of the IBM machines might have bi-directional parallel ports, but the implementation is not quite what everybody else expects. For example, the PS/2 Model 25 has a bi-directional parallel port but the Xircom PE3-10 adapters do not detect it because the port to control the behavior is in a non-standard place.

DOS 5 definitely allows more than 32MB when compared to DOS 3.3 - I had not realized you were going to attach mass storage. It should work, but it will be slow. Just enjoy it for what it is.

 

[motley2659]

What thread?

I don't think I have tested the speed of the parallel port on the IBM 5140. I don't think it is ever going to hit 150KB/sec though. It's a very slow machine (under 10Mhz.)

I misremembered. It wasn't you that started the thread.

http://www.brutman.com/forums/viewtopic.php?f=1&t=299

Anyway, this is what "James" had to say about the PCjr parallel and the CF card reader.

I finally got around to testing the parallel port CF card reader. It works. It is a DataFab Image Reader, Model MDCFE-SR. So far I've tested it with and 8 MB card but I should be able to use it with any card upto 32 MB since I am running DOS 3.3. It will be another way of getting data on and off the PCjr. What also is good is it has a parallel passthough which works with the Xircom parallel port ethernet card. You can't use them at the same time but it eliminates disconnecting until I can get a second parallel port setup. The keyboard power adapter is not compatible with our keyboard jack but there are always other sources of the required 5V.

I currently have the jrIDE, so I don't need it for mass storage but it works for that as well. I successfully ran a few games off of it. Overhead is about 50K.

Amazon actually has a few of them for $10 each.

 

[Great Hierophant]

The parallel port adapter will also be slow, especially in the 4.77MHz 80C88 machine with a unidirectional port. The 50K that the device driver takes up, in addition to the ~65K that DOS 5.0 takes, will pinch. I hope you can upgrade your system to 640KB. IBM only supported 512KB with their upgrade cards.

As far as Wasteland goes, you should see something like this :





or this :





The first set is if you install the RGB graphics. The second set is if you install the composite color graphics. You need the original floppy disks to install anything other than EGA graphics.

 

[motley2659]

Wow, so I'll be going the RGB version then. I do have the original files for Wasteland (it's about 1.5mb total) so I'll run the setup and convert to regular CGA.

I just got it in the mail today and it has 640kb. I haven't had time to tinker with it more than a few minutes but it's faster than I thought it would be, and the keyboard is excellent.

The Datafab reader is on its way and I'm about to take the plunge on a 5144 monitor. When I get the the CF Card Reader in, I'll do some tests and report back on the performance.

 

[motley2659]

The parallel port adapter will also be slow, especially in the 4.77MHz 80C88 machine with a unidirectional port.

We still don't know if it is unidirectional or bidirectional. The PCjr is definitely uni, but I searched high and low and there is little commentary on the IBM 5140 Parallel Port slice's capabilities, as far as that goes.

Regardless, even if I only get a ~50K/s transfer rate, I'll still save some wear and tear on my floppy drives.

The 50K that the device driver takes up, in addition to the ~65K that DOS 5.0 takes, will pinch. I hope you can upgrade your system to 640KB. IBM only supported 512KB with their upgrade cards.

I have 640k on the system. Assuming all this is true (the Datafab memory hogging is unknown), that still leaves me with over 512K available memory. That will give me plenty of memory for Xywrite, Lotus, and Sidekick. And most games that require 640K- which also have CGA compatibility- run too slow on an 8088 anyway. Well, except for Ultima Vi, supposedly.

 

[Great Hierophant]

We still don't know if it is unidirectional or bidirectional. The PCjr is definitely uni, but I searched high and low and there is little commentary on the IBM 5140 Parallel Port slice's capabilities, as far as that goes.

Regardless, even if I only get a ~50K/s transfer rate, I'll still save some wear and tear on my floppy drives.



I have 640k on the system. Assuming all this is true (the Datafab memory hogging is unknown), that still leaves me with over 512K available memory. That will give me plenty of memory for Xywrite, Lotus, and Sidekick. And most games that require 640K- which also have CGA compatibility- run too slow on an 8088 anyway. Well, except for Ultima Vi, supposedly.

The technical reference does not mention any bidirectional capabilities for the card, but if the expansion uses discrete logic chips, it can be modified.