IBM 5140 ISA Bus connector

[Defiant1Dave]

OK...... Let's get semi-serious about building a REAL expansion unit for the 5140..... with a proper HDD and a few expansion slots.

I've done a little research into the 5140's expansion bus connector. As expected, it IS an 8-bit ISA architecture, and contrary to what one website states, it is NOT a multiplexed 16-bit ISA bus. That being the case, it should be relatively easy to construct a TRUE 5140 Expansion unit, instead of relying upon Interlnk Servers.

So here's what I'm thinking- a free standing box with an 8-bit riser..... maybe 5 slots..... and it's own power supply. Then there'd be a little adapter of some sort, matching the ISA riser to the 72 port edge connector. Finally, there'd be an edge connector male / edge connector female cable going from the expansion unit to the computer itself.

In the FIRST slot, I'd put a Hardcard 20 or 40 which should talk to the ISA bus and 5140 just fine, since it has it's own BIOS...... thus eliminating the need to modify the 5140's bios. (maybe)

To make this happen, I need some data: Specifically, I need the pin-outs for the 72 connection edge-connector on the rear of the 5140.

I ALSO need a few bits of hardware..... parts and pieces:
1. any dead 5140 expansion modules that I can steal the edge connectors from
2. an 8-bit riser card........ OR a plain16-bit one, without any circuitry.
3. a Cool Cabinet to put it all in
4. any 8-bit cards that might play well with the 5140..... especially any 8-bit game ports, I/O ports, or memory cards.

So..... that's my shopping list. I'm accepting donations to the cause in the form of of information and hardware. In return, I'll post my design, successes, rants, and failures right here so that everyone can build their own units..... and/or get a good laugh at such an absurd undertaking!

 

[mbbrutman]

From the Tech Ref, courtesy of RJBJR ..

5140 Pin	Name				In/Out
		
1		Shell ground			Ground
2		+Address Latch Enable		Output
3		+5 V dc				Power
4		+ Address Enable		Output
5		+I/O Channel Ready		Input
6		Ground				Ground
7		Spare	
8		Ground				Ground
9		-I/O Channel Check		Input
10		+Sleep Clock			Output
11		Terminal Count			Output
12		+12 V dc			Power
13		-I/O Write			Output
14		-Memory Read			Output
15		-Memory Write			Output
16		+Adapter Power			Power
17		+Address Bit 10			Output
18		+Address Bit 11			Output
19		+Address Bit 12			Output
20		+Address Bit 13			Output
21		+Address Bit 14			Output
22		+Address Bit 15			Output
23		+Address Bit 16			Output
24		+Address Bit 17			Output
25		-13 V dc			Power
26		Ground				Ground
27		+Address Bit 18			Output
28		+Address Bit 19			Output
29		+Power Adapter Active		Output
30		+Printer Power			Power
31		Ground				Ground
32		-Transmit Data			Output
33		-Printer Error			Input
34		+Printer Enable			Output
35		-Printer Busy			Input
36		Shell Ground			Ground
37		+Address/Data Bit 0		Input/output
38		+Address/Data Bit 1		Input/output
39		+Address/Data Bit 2		Input/output
40		+Address/Data Bit 3		Input/output
41		+Address/Data Bit 4		Input/output
42		+Address/Data Bit 5		Input/output
43		+Address/Data Bit 6		Input/output
44		+Address/Data Bit 7		Input/output
45		+Address Bit 0			Input/output
46		Ground				Ground
47		+Address/Data Bit 9		Input/output
48		+Interrupt Request 4		Input
49		-I/O Read			Output
50		+Reset				Output
51		-Data Enable			Output
52		Reserved	
53		Ground				Ground
54		+DMA Request 1			Input
55		-DMA Acknowledge 1		Output
56		Ground				Ground
57		+DMA Request 2			Input
58		-DMA Acknowledge 2		Output
59		+DMA Request 3			Input
60		Ground				Ground
61		-DMA Acknowledge 3		Output
62		+Interrupt Request 2		Input
63		+Interrupt Request 3		Input
64		Ground				Ground
65		+Interrupt Request 6		Input
66		Spare	
67		+Interrupt Request 5		Input
68		Spare	
69		Reserved	
70		+Power Enable			Output
71		Ground				Ground
72		+Interrupt Request 7		Input

Page scans probably work better - I'll work on those later.

The next step is to map the pins to their ISA equivalents. I did something similar for the PCjr: http://brutman.com/PCjr/pcjr_isa_adapter.html


Mike

 

[Defiant1Dave]

you are THE MAN!

you are THE MAN!

Mike... that is just what I'm looking for!

I've got the ISA architecture, so now it's just a matter of mapping things out.

I have an old I/O board from a derelict 5140 printer, and the line numbers used for the printer there match up with the numbers on the chart for the printer. The rest are straight-through. (They are the actual ISA bus.) It also has a very nice pair of connectors, and a set of line numbers printed on the board....... so figuring out wiring map should not be too difficult.

Now I need to find an ISA riser card. I think e-bay might be my next stop.

Thanks!

 

[Great Hierophant]

Other than a few issues with the pinout, an expansion unit should not be too difficult.

I think Pin 25 should be -12v, Pin 45 Address Bit 8 and Pin 47 only Address Bit 9.

There is no -5v, CLK or OSC signals present. A 7905 voltage regulator on the -12v line should give a -5v signal and a 14.318180MHz crystal oscillator in the expansion tied to an Intel 8284 can take care of the latter two (although they may be out of phase with the system clock.)

The Data Bus is multiplexed with the lower 8-bits of the Address Bus, so a simple demultiplexer will need to be fashioned. Since the signals are multiplexed out of the processor, the first page of the PC or XT schematics should provide the proper circuit.

 

[Defiant1Dave]

ok....after looking over the pin-outs, mapping them out, and doing a quick sketch of the expansion bus, I must admit that I'm considering dropping the project. I investigated the de-mux chip, and designed the circuitry...... and then decided that the entire project is just too limited in scope to be worth the effort. About the only thing I'd gain is a HDD.... and my junk-box server is serving quite nicely for storage purposes. SO.... I think this one is goin to sit on the back burner for a while as I ponder it's usefulness.

It all reminds me of what Jeff Goldbloom said in Jurasic Park 2..... Just because we CAN do something doesn't mean we SHOULD. In this case, it looks like too limited a return.

 

[mbbrutman]

I have found that besides having a hard drive, having a network card is a great addition to old machines. On my PCjr I routinely use an XT-IDE and an ISA network card. In the past I've used SCSI carts, parallel printer port cards, etc.

The performance is infinitely better than what you can get from parallel port attached devices. And the 5140 is limited to one parallel port, unlike other machines. (Unless you can find and hack the adapters, which are not common.)


Mike