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bettablue
April 21st, 2011, 06:50 PM
Now that I have the 5150 computer system I have always wanted, I would like to find an IBM 5161 expansion unit to go along with it. I haven't seen any on EBay or any of the other sites I frequent, so I'm asking here. Does anyone know where to get a line on one of these? I would like to find one with a 10 Meg hard drive installed, but I won't be too pickey, If I can get one, I'll buy a hard drive seperately if I have to.

Thanks much.

Ole Juul
April 21st, 2011, 09:20 PM
You'll need 5 items for one of those. Case, backplane, cable, receiver, transmitter. I have the two cards if you want, but not the other three items.

per
April 22nd, 2011, 08:06 AM
The chassis is just a regular XT-chassis with the keyboard port blocked by a plug. The powersupply is just the same as in the XT.

The backplane is also just a regular 8-bit ISA-bus with 8 ports wiered in parallel. It also has a simple Intel 8284 clock generator providing a 50%-duty 14.318MHz squarewave clock for the "OSC" signal, and a power input connector for the PSU.

The Transmiter/Receiver cards does all the magic. It buffers the signals, and it provides certain debugging features where the address/data lines of the bus in the expansion unit can be programmed/controlled and monitored by the CPU.

The cable is problably the most difficult part to get. It has a special pinout, but once heard that some company have attempted to make replacements (unless I remember wrongly). It may also easily break as it consist of almost 30 smaller wires which all carries their own dedicated signal. If any of these wires break; corruption will occour.

It's relatively difficult to find everything, but it shouldn't be hard to make something similar if you have the interface cards and cable, and if you can live with the fact that's it's not 100% original. When they show up complete and in working condition, you may expect to pay a decent amount of money. I bought mine for around €100.

-----

Also note that the expansion unit will not work in XT's with the second or third BIOS revision, which means that you will need an pre-1986 XT to use it. I have a hypothesis that later XTs with the second or third were modified to not accept 8KB EPROMs, which may complicate the process of downgrading the BIOS to the first-version. However, nobody has been able to confirm this.

MikeS
April 22nd, 2011, 08:37 AM
The chassis is just a regular XT-chassis with the keyboard port blocked by a plug...... and a different name on the front ;-)

bettablue
April 22nd, 2011, 07:22 PM
Paying $100.00 or so is completely acceptable to me. Of course, I know I'll be paying for shipping too. If you happen to know where I can get one, please let me know.

Thanks much for the info.



The chassis is just a regular XT-chassis with the keyboard port blocked by a plug. The powersupply is just the same as in the XT.

The backplane is also just a regular 8-bit ISA-bus with 8 ports wiered in parallel. It also has a simple Intel 8284 clock generator providing a 50%-duty 14.318MHz squarewave clock for the "OSC" signal, and a power input connector for the PSU.

The Transmiter/Receiver cards does all the magic. It buffers the signals, and it provides certain debugging features where the address/data lines of the bus in the expansion unit can be programmed/controlled and monitored by the CPU.

The cable is problably the most difficult part to get. It has a special pinout, but once heard that some company have attempted to make replacements (unless I remember wrongly). It may also easily break as it consist of almost 30 smaller wires which all carries their own dedicated signal. If any of these wires break; corruption will occour.

It's relatively difficult to find everything, but it shouldn't be hard to make something similar if you have the interface cards and cable, and if you can live with the fact that's it's not 100% original. When they show up complete and in working condition, you may expect to pay a decent amount of money. I bought mine for around €100.

-----

Also note that the expansion unit will not work in XT's with the second or third BIOS revision, which means that you will need an pre-1986 XT to use it. I have a hypothesis that later XTs with the second or third were modified to not accept 8KB EPROMs, which may complicate the process of downgrading the BIOS to the first-version. However, nobody has been able to confirm this.

bettablue
April 23rd, 2011, 12:47 PM
I am curious now. Is all it takes is to get a 5160 CPU unit and the parts to convert it? Assuming I have the transmitter and receiver cards and the cable, From what I understand at this point, all I will need to complete it would be the 5160 CPU unit/case and the back plate. Are there any instructions for converting from a 5160? I can get a 5160 without problem. I guess I will then need to see if I could find the back plate.




[QUOTE=per;176636]The chassis is just a regular XT-chassis with the keyboard port blocked by a plug. The powersupply is just the same as in the XT.

The backplane is also just a regular 8-bit ISA-bus with 8 ports wiered in parallel. It also has a simple Intel 8284 clock generator providing a 50%-duty 14.318MHz squarewave clock for the "OSC" signal, and a power input connector for the PSU.

The Transmiter/Receiver cards does all the magic. It buffers the signals, and it provides certain debugging features where the address/data lines of the bus in the expansion unit can be programmed/controlled and monitored by the CPU.

The cable is problably the most difficult part to get. It has a special pinout, but once heard that some company have attempted to make replacements (unless I remember wrongly). It may also easily break as it consist of almost 30 smaller wires which all carries their own dedicated signal. If any of these wires break; corruption will occour.

It's relatively difficult to find everything, but it shouldn't be hard to make something similar if you have the interface cards and cable, and if you can live with the fact that's it's not 100% original. When they show up complete and in working condition, you may expect to pay a decent amount of money. I bought mine for around €100.

-----

Also note that the expansion unit will not work in XT's with the second or third BIOS revision, which means that you will need an pre-1986 XT to use it. I have a hypothesis that later XTs with the second or third were modified to not accept 8KB EPROMs, which may complicate the process of downgrading the BIOS to the first-version. However, nobody has been able to confirm this.

per
April 23rd, 2011, 01:26 PM
I am curious now. Is all it takes is to get a 5160 CPU unit and the parts to convert it? Assuming I have the transmitter and receiver cards and the cable, From what I understand at this point, all I will need to complete it would be the 5160 CPU unit/case and the back plate. Are there any instructions for converting from a 5160? I can get a 5160 without problem. I guess I will then need to see if I could find the back plate.

Not a 5160 CPU, but a 5160 chassis with PSU (= Powersupply). You will have to make the backplane yourself if you take that approach, but then you'll not even need a proper XT-chassis as you can make the homemade backplane fit any chassis you wish.

To make the backplane you need 8 8-bit ISA slots, some big piece of PCB prototyping board, an 8284, a 14.31818MHz crystall, some minor parts, wires, soldering skills and the schematics from the IBM techref. The soldering-job will take some time, but it shouldn't be too difficult as the design is really simple. Just remember to place the capacitors in the correct spots between the slots and not in a cluster as the schematics may seems like.

When you have the backplane mounted in whathever chassis you choose to use (and after hooking up the powersupply), you actually only need the interface cards and the cable. The cable will need a Male DB62HD (aka. HD62M or DC-62P) connector in each end, with every line connected between the two connectors. The cable by IBM is assumed to provide an average delay of approximately 3ns. I assume This (http://www.amazon.com/62-Pin-HD62-Deluxe-D-Sub-Cable/dp/B003MZS5DO) should work well.

But still, only an XT with the first BIOS will be able to activate the interface. Generally speaking; this means that XTs with half-height FDDs from IBM and a 256KB-640KB motherboard will not work.

per
April 23rd, 2011, 02:12 PM
Actually, on second thougths, I think the 5150s with the third BIOS may also have support for the expansion interface. There is basically very little difference between the 64-256KB PCs and the early-configuration XTs, and most of the differences are in how minor things are implimented on the motherboard.

JohnElliott
April 23rd, 2011, 03:24 PM
What support does the interface need from the BIOS, and is this something that could be replicated with a loadable driver if necessary?

modem7
April 23rd, 2011, 04:50 PM
An earlier thread that discusses "non-supported" 5160 models is at: http://www.vintage-computer.com/vcforum/showthread.php?2772

An IBM technical document (including circuit diagrams) on the 5161 is at http://members.dodo.com.au/~slappanel555/oa/oa.htm

Which IBM cards are allowed/disallowed in the 5161 is in the 'System to Adapter Compatibility Chart' within the following document:
http://members.dodo.com.au/~slappanel555/oa/OA%20-%20Vol1%20-%20Title%20pages.pdf

Lorne
April 23rd, 2011, 06:25 PM
The cable will need a Male DB62HD (aka. HD62M or DC-62P) connector in each end, with every line connected between the two connectors. The cable by IBM is assumed to provide an average delay of approximately 3ns. I assume This (http://www.amazon.com/62-Pin-HD62-Deluxe-D-Sub-Cable/dp/B003MZS5DO) should work well.



This one definitely works, and it's cheaper.
http://cyberresearch.com/store/cables-wiring/pc-computer-cables/CBL_6203_7356.2.htm
It's what I'm using instead of wearing out my IBM cable.
A 3' cable is plenty if it's got a 5150 sitting right on top of it.

Lorne
April 23rd, 2011, 06:35 PM
Actually, on second thougths, I think the 5150s with the third BIOS may also have support for the expansion interface. There is basically very little difference between the 64-256KB PCs and the early-configuration XTs, and most of the differences are in how minor things are implimented on the motherboard.

With my 5161, I'm using an earlier 5150 (16-64KB board) and the 1501476 ROM BIOS.
The earlier BIOS wouldn't support it, so I had to switch it.

per
April 24th, 2011, 04:13 AM
This one definitely works, and it's cheaper.
http://cyberresearch.com/store/cables-wiring/pc-computer-cables/CBL_6203_7356.2.htm
It's what I'm using instead of wearing out my IBM cable.
A 3' cable is plenty if it's got a 5150 sitting right on top of it.

Only the 3' cable on that site is cheaper, the other lengths are cheaper on the site I provided. The $34 example on the Amazon page was for the 10ft version.

A thought on quality: The original IBM cable uses a copper-width of 22AWG, which is an area of 0.326 square-mm per wire (18.256 qube-cm copper for every meter of 56-wire cable). The cable I listed uses 28AWG, which is 0.0810 square-mm per wire (5.020 qube-cm per meter 62-wire cable). The original IBM cable has in other words about 4 times as much copper, which explains the difference in the cable-width. This also suggests that the modern cables are even more fragile than the original IBM one. The site Lorne reffers to doesn't state what copper width it uses, but I assume it's around 28AWG as well.

Lorne
April 24th, 2011, 05:31 AM
Correct per - it's like almost everything made back then. They were made to last (and copper was a whole lot cheaper back then too!).

That original cable is a beast - it's very difficult to bend that cable to get it to go where you want it to.
That's why I bought the replacement cable. At least you can bend that 3' cable.