🚀 go-pugleaf

After wondering for a while how to get COM3 and COM4 support,
I finally figured out how to patch COM01.SYS to make it support
COM3 COM4.   That is, a separate copy that only knows COM3, COM4,
and has a different name.  I don't know if my version is like 
everyone elses, so I will only give the general idea.  If they are,
I can give specific PATCH instructions.

The COM1, COM2 in the device header should be changed.
Another COM1, I don't know what it is for.

At offset 2276 and 2280, (use PATCH command to see it.)
are x'03f8' and x'02f8' which should be changed to respective addresses.

Offset 2273 and 227d are x'04' and x'03', which are interrupt vectors.
These should be changed.  Multiple devices on the same vector are NOT
supported.  Your card (I have Jameco 1062) must support more.

The instructions to load the port addresses from 400, 402 must be
changed to ones that set the address, unless your BIOS loads 404, 406.

From:
  MOV AX,40
  MOV ES,AX
  MOV BX,[0BD5]
  SHL BX,1
  MOV  DX,ES:[BX]

To:

  MOV DX,02E8
  TEST [0BD5],1
  JNZ .+5
  MOV DX,03E8
  NOP

The code which zeroes out the 400, 402 

  MOV [BX],0000

should be NOP'ed out.

I currently have COM3 on IRQ5 (turn off LPT2) working.
COM4 on IRQ2 --> interrupt vector 9, may not work.  Then again,
I may have a defective cable.  It is a 9 pin connector of this board.

The documentation for DevHlp SetIRQ seems to require vector 9 for IRQ2,
and it is supposed to be redirected.  Well, the IRQ2 bus line goes to
interrupt line 9.  This may not work for some other reason, I only
tested it once.  I am writing this while logged in on COM3.

Good Luck.