        This technical note documents the use of the IBM ISA Twinax card (or clone) in conjunction with an APPC Router and WinAPPC environment. Getting the IBM ISA Twinaxial adapter card to work while under Windows can be troublesome unless it is carefully installed. The MCA adapter is somewhat simpler as the ADF file does automatically resolve some, but not all, of the conflicts. The IBM adapter uses the following PC resources: I/O address, Shared RAM, and a Hardware Interrupt (IRQ). Any and all of these adapter interfaces can conflict with other equipment in the PC giving intermittent or complete failures. With PCs frequently containing LAN, Sound and SCSI adapters, not to mention that Windows attempts to control much of the PC resources, conflicts can easily occur. ----------- Shared RAM: The most complex to handle, as multiple software programs in the PC will attempt to allocate and use all the memory they can, is the adapter Shared RAM (memory) access. The IBM ISA adapter has a 8K Shared RAM window and the MCA has an 16K window. It is always recommended that you exclude all of video RAM (A000-C7FF) to ensure that no program is attempting to use that area. (IBM recommends excluding just B000-B7FF of video RAM). First, you must determine an area of memory that is available for use. Before you have the IBM card installed, use MSD (Microsoft Diagnostic) that comes with MS-DOS 6.xx and Windows to determine if any of the following memory ranges are currently unused: BC00-BDFF, CC00-CDFF, DC00-DDFF, or EC00-EDFF. Second, you must configure your memory management software to exclude the selected range of memory from available RAM that it can used by the IBM adapter. If using HIMEM and EMM386, a possible CONFIG.SYS fragment is:
DEVICE=C:\DOS\HIMEM.SYS
DOS=HIGH,UMB
DEVICE=C:\DOS\EMM386.EXE NOEMS X=DC00-DDFF X=A000-C7FF
Third, you must inform Windows to not use that area of memory as well.
In the SYSTEM.INI file, find the [386Enh] section and add the necessary
lines:
[386Enh]
EMMExclude=A000-C7FF
EMMExclude=DC00-DDFF
TimerCriticalSection=500
The TimerCriticalSection entry is optional, but does help in some
configurations where the DOS TSR does not have enough time to complete
it's work.
Last, you must tell the IBM PCS/400 (or CA/400) adapter handler where the card memory is to be placed. In the STARTPCS.BAT (or equivalent batch file):
E5250AH /MD
The /M command line parameter (switch in Microsoft lingo) specifies
the memory page (the first character in the memory address) where
the adapter is to place it's Shared RAM. For example: /MC specifies
CC00-CDFF, /MD specifies DC00-DDFF, and /ME specifies EC00-EDFF.
The default value is /MD for DC00-DDFF.
ALL THREE MEMORY SETTINGS (config.sys exclude, system.ini exclude, and the adapter handler memory specification) MUST AGREE (match)!! ----------- I/O address: The I/O address is what the adapter handler uses to tell the IBM adapter where it should locate the Shared RAM range and which IRQ to use. This MUST be in an unused area of I/O space. Fortunately the I/O map is a relatively abundant PC resource (sparsely used). A complication to I/O usage is that many adapters do not decode all 16 bits of the I/O address value. Consequentially, even if the IBM adapter is mapped to a value far outside the range of other adapters, sometimes the other adapters may see I/O to the IBM as I/O to them causing them to malfunction or even interfere with the IBM I/O conversation. For example, it is reported that older Ethernet cards that default to I/O addresses of 0x300 can sometime cause problems. The adapter handler /I command line parameter (switch) specifies the CENTER two digits of the base I/O address to use. For example, /I71 specifies address 2718 and /I7E specifies 27E8. See the table at the end of this document for a comprehensive list of IBM settings. The default IBM setting is 2718. A good alternate is 27E8.
E5250AH /I71
THE I/O ADDRESS SELECTED MUST MATCH THE VALUE SET ON THE ADAPTER DIP
SWITCH SETTINGS (or the ADF value for the MCA adapter).
----------- IRQ (Hardware Interrupt): The IRQ (adapter hardware interrupt) is a system resource not (easily) shareable between adapters. This value typically runs from 2 to 7. Again MSD can inform you of what IRQs are already being used by equipment in your PC. IRQs 3 and 4 are generally taken by async communications COM1 and COM2. IRQ 6 is used by the Floppy drive controller. IRQ 7 is generally taken by the printer ports. To change this value from the default of 5 specify the /L command line parameter (switch) specifies the IRQ level. The following example specifies IRQ 5.
E5250AH /L5
Many machines have a problem using IRQ 5. Alternatives that might work
better are 7 (which can cause printer problems) and 2 (which can cause
performance problems for programs sharing the daisy-chain interrupt).
----------- General comments: Given the amount of PC resources required to use the IBM twinaxial adapter, it can difficult to find the available resources in PCs today. It can be made to work, but new installations should seriously consider whether to make a new purchase of the IBM adapter or a 3rd party adapter that uses far few resources. One abnormal problem that we experienced in-house was a early release ATI Graphics Pro Turbo (Mach64) video driver was causing PCS/400 to fail using the IBM twinax adapter. Upgrading the ATI driver to v1.31 resolved the problem completely. ----------- I/O address -> Switch setting -> Adapter handler parm table Note the 2 entries in the I/O address column. The 16 bit column is the "true" I/O address values (e.g. 240x means 2400 thru 240F) and the 10 bit entry is what the I/O address would be if the top most bits were not decoded (see comments above concerning the I/O address setting and other adapter cards). For example if the IBM twinax adapter setting was for 270x (2700-270F) then it watch for adapters set for 30x (300-30F) as they might possible conflict.
---- I/O address ---- Switch settings Adapter handler
16 bits 10 bits 123456 command line parameter
240x 00x 000010 /I40
241x 01x 100010 /I41
242x 02x 010010 /I42
243x 03x 110010 /I43
244x 04x 001010 /I44
245x 05x 101010 /I45
246x 06x 011010 /I46
247x 07x 111010 /I47
248x 08x 000110 /I48
249x 09x 100110 /I49
24Ax 0Ax 010110 /I4A
24Bx 0Bx 110110 /I4B
24Cx 0Cx 001110 /I4C
24Dx 0Dx 101110 /I4D
24Ex 0Ex 011110 /I4E
24Fx 0Fx 111110 /I4F
250x 10x 000000 /I50
251x 11x 100000 /I51
252x 12x 010000 /I52
253x 13x 110000 /I53
254x 14x 001000 /I54
255x 15x 101000 /I55
256x 16x 011000 /I56
257x 17x 111000 /I57
258x 18x 000100 /I58
259x 19x 100100 /I59
25Ax 1Ax 010100 /I5A
25Bx 1Bx 110100 /I5B
25Cx 1Cx 001100 /I5C
25Dx 1Dx 101100 /I5D
25Ex 1Ex 011100 /I5E
25Fx 1Fx 111100 /I5F
260x 20x 000011 /I60
261x 21x 100011 /I61
262x 22x 010011 /I62
263x 23x 110011 /I63
264x 24x 001011 /I64
265x 25x 101011 /I65
266x 26x 011011 /I66
267x 27x 111011 /I67
268x 28x 000111 /I68
269x 29x 100111 /I69
26Ax 2Ax 010111 /I6A
26Bx 2Bx 110111 /I6B
26Cx 2Cx 001111 /I6C
26Dx 2Dx 101111 /I6D
26Ex 2Ex 011111 /I6E
26Fx 2Fx 111111 /I6F
270x 30x 000001 /I70
271x 31x 100001 /I71
272x 32x 010001 /I72
273x 33x 110001 /I73
274x 34x 001001 /I74
275x 35x 101001 /I75
276x 36x 011001 /I76
277x 37x 111001 /I77
278x 38x 000101 /I78
279x 39x 100101 /I79
27Ax 3Ax 010101 /I7A
27Bx 3Bx 110101 /I7B
27Cx 3Cx 001101 /I7C
27Dx 3Dx 101101 /I7D
27Ex 3Ex 011101 /I7E
27Fx 3Fx 111101 /I7F
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