J1 VGA Passthrough JP1 Reserved JP2 Reserved JP5 IRQ Q1  4.000 Mhz xtal U1-4  MT42C8255DJ  -8

U10  inmos IMSG191F 88S U16  BIOS U19  28.322000 MHz osc  U20  inmos IMSG200X-40S U28  MT5C2568DJ  -45 U29  inmos IMSG010JA

U16 = PhoenixVIEW VGA-Compatible BIOS, 1985-1991   A 11055
JP5 sets IRQ. From left to right IRQ14, 13, 12, 11, 10 

Notes: 
1. Driver equivalent with the MCA variant.
2. Responds to MCA ID & settings polling.
3. OS/2 2.0 could not identify it, XGARING0.SYS has been fixed later.
4. May require a DOS driver in CONFIG.SYS to assure DMA channel.
5. Aperture disabled per default.

NOTE: SW1 and SW2 were made by different manufacturers. 
UP, OPEN, and OFF are used interchangeably.

2 ROM    UP ROM Enabled
         DN ROM Disabled *

3 IOS    UP 8 or 16 bit I/O cycles *
         DN 8 bit I/O cycles only

4-6 INSTx  x=2,1,0 (XGA Instance)
           4  5  6
Inst0      D  D  D
Inst1      D  D  U
Inst2      D  U  P
Inst3      D  U  U
Inst4      U  D  D
Inst5      U  D  U
Inst6      U  U  D *
Inst7      U  U  U

7-8 DMAx  x=1,0
           7  8
No DMA     D  D
DMA 6      D  U
DMA 7      U  U  *

2 FPP     Reserved, must be UP

3-4 RSx  x=0,1 ROM Base address
           3  4
C0000h     D  D  *
C8000h     D  U
D0000h     U  D
D8000h     U  U