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Build Options
640KB edited this page Sep 23, 2025
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Below are the configurable options to build GLaBIOS for different systems that may be edited in GLABIOS.ASM.
Important build note: Not all options may be enabled simultaneously due to limited 8K of ROM storage. If experimenting with options, it's strongly recommended to build using MASM 5.x as it will produce an error if code space is exceeded. See How to Build.
Set CPU_TYPE to enable compatible instructions to use during build time. Selecting V20 enables the use of instructions that are specific to only the NEC V-series CPU. If unsure, it is recommended to use CPU_8088.
CPU_TYPE |
Code | Architecture | Description |
|---|---|---|---|
CPU_8088 |
8 |
Intel x86 | All Intel CPUs (8088, 8086, 80x86, NEC) |
CPU_V20 |
V |
NEC V-series | NEC V20, V30, V40 only |
Set ARCH_TYPE to the defined preset type below inline in code or at assemble type using MASM option /DARCH_TYPE='X' (for ARCH_5160).
ARCH_TYPE |
Code | Architecture | Description |
|---|---|---|---|
ARCH_5150 |
P |
PC 5150 | Supports 5150 SW1/SW2 and Cassette interface |
ARCH_5160 |
X |
PC 5160 | Standard XT, or non-Turbo clones |
ARCH_TURBO |
T |
Standard Turbo | Typically discrete components, uses PPI for software turbo control |
ARCH_TD3300 |
S |
TD3300A | Juko ST-12, UNIQUE, Auva |
ARCH_FE2010 |
F |
Faraday FE2010A | |
ARCH_UM82 |
U |
UMC UM82C088, ALi M1101 | |
ARCH_EMU |
E |
86Box/Emulators | Removes I/O wait times and hardware checks for additional speed. Not for real hardware. |
ARCH_EHB |
H |
EMM Homebrew 8088 | |
ARCH_BOOK88 |
B |
Book 8088 |
These are based on one of the above types but slightly vary in configuration.
ARCH_SUB_TYPE |
Code | Architecture | Sub-type of | Description |
|---|---|---|---|---|
ARCH_5160v2 |
Y |
PC 5160v2/v3 | ARCH_5160 |
Reserved (unused) |
ARCH_M88 |
M |
micro_8088/NuXT | ARCH_FE2010 |
|
ARCH_NEST |
N |
Juko Nest N3 | ARCH_TD3300 |
8086/V30 |
ARCH_VEN888 |
V |
Vendex 888-XT | ARCH_TURBO |
Custom Turbo speed register |
ARCH_MARTY |
C |
MartyPC Emulator | ARCH_TURBO |
|
ARCH_VIRTUALXT |
J |
VirtualXT Emulator | ARCH_TURBO |
|
ARCH_MIST |
I |
PCXT_MiSTer | ARCH_EMU |
Experimental |
Some motherboards boot in normal (slow) mode by default and the BIOS may or may not switch to Turbo speed on boot. Others invert this behavior where it appears reversed to the BIOS. Use these options to customize for your motherboard.
TURBO_TYPE |
Description |
|---|---|
TURBO_NONE |
Fixed clock speed PC, XT or clone |
TURBO_STD |
PPI 61h bit 2 (1=turbo, 0=normal) |
TURBO_REV |
PPI 61h bit 2 (1=normal, 0=turbo) |
Enable/Disable POST tests
| Option | Default | Description |
|---|---|---|
POST_TEST_INST |
0 |
POST CPU Instruction/Flag Test |
POST_TEST_DMA |
1 |
POST DMA Register Test |
POST_TEST_DMA_TC0 |
1 |
POST DMA Terminal Count Test |
POST_TEST_PIT_1 |
1 |
POST Timer Channel 1 Test |
POST_TEST_PIC_REG |
1 |
POST PIC Register Test |
POST_TEST_PIC_INT |
1 |
POST PIC Interrupt Test |
POST_TEST_CHK_ROM |
1 |
POST Checksum ROM |
POST_TEST_FD |
1 |
POST Floppy Drive Test |
POST_TEST_SEEK |
1 |
POST Seek Floppy Drives |
POST_TEST_KB |
1 |
POST Keyboard Test (PKI) |
POST_TEST_KEY |
1 |
POST Key Test (PKEY) |
| Option | Default | Description |
|---|---|---|
BASIC_ROM |
1 |
BASIC ROM support at 0F600h
|
FDC_ADV_SEEK |
1 |
Cache drive head position in memory to reduce FDC I/O for sequential reads on same track. Can significantly improve read performance. |
FDC_ENABLE |
1 |
1=Enable standard INT 13h floppy support0=disable floppy support completely (use only if no floppy controller installed) |
FDC_IPL_SW |
0 |
Use IPL switch (SW1-1) to indicate no floppy controller/drives are installed. This is the behavior as 5150 and some later high-density FDC BIOSes. |
LIGHT_PEN |
1 |
INT 10h,4 CGA/MDA light pen support.May be disabled if additional code space is required. |
MAX_RAM_AUTO |
0 |
Set maximum detectable low memory based on video DIP switches: EGA/VGA = 640K, MDA = 736K, CGA = 704K |
MDA_ATTR |
1 |
Filter MDA character attributes to improve visibility of MDA adapters or monitors with non-standard attributes or low contrast2=allow all, 1=intensity only, 0=filter all |
MUTE_TANDY |
0 |
On boot, mute power-on noise on Tandy 3 Voice or SN76489AN |
OEM_FONT |
0 |
1=use OEM style CGA mode 4-6 font, 0=clone style |
OEM_KB_EXT |
1 |
Allow EAh cold reset byte from extended/enhanced keyboards |
OPT_ROM_END |
0FE00H |
Option ROM scan end segment. Default scan all segments between C800-FD80 for option ROMs. |
POST_CARD |
0 |
Enable POST codes on port 80H, corresponding to POST error beeps
|
POST_ERR_WAIT |
1 |
1=Wait for Any Key press to continue if there is a POST error0=Only display error and continue booting |
POST_HD_PARMS |
1 |
Enable POST hard drive drive count, size and geometry. May be disabled if additional code space is required. |
POST_OPT_ROM |
1 |
Show detected option ROM address and size. May be disabled if additional code space is required. |
RAM_PARITY |
1 |
Enable RAM parity checking. |
RANDOM_TAGLINE |
1 |
Show a randomized pithy tagline. |
UNITS_IEC |
0 |
Display units as 0=period-correct "KB" or 1=modern IEC "KiB" |
These options may be used by emulator developers or for specific hardware use cases. It is recommended to leave these as-is
| Option | Default | Description |
|---|---|---|
DRAM_REFRESH |
18 |
DRAM refresh divisor use standard PC timing of 1.193 MHz/18 = 66,287.87 Hz (see UNSAFE_REFRESH ) |
EXP_UNIT |
0 |
Init 5161 I/O Expansion Unit (may not be necessary) |
FD_AUTO_DETECT |
0 |
Auto-detect number of floppy drives on systems that do not have drive count switches, such as FE2010 |
FDC_ERR_SEC_CT |
0 |
On INT 13h read, write or verify operation errors:0=always return 0 sectors even if some sectors have been successfully read (PC typical behavior)1=return partial/successful sector count |
FDC_HLT_WAIT |
1 |
Halt CPU (HLT) during FD I/O (this can cause issues on TD3300A due to unknown chipsets bugs) |
FDC_ZERO_BDA |
0 |
Clear FDC FIFO buffer between operations. This is not normally necessary and can cause issues with software/BIOSes that use this memory (Seagate MFM BIOS). |
FE_CONF_LOCK |
1 |
Lock FE2010 config register after init. |
FEATURE_BYTES |
1 |
Encodes flags for most configurable build options into ROM binary for future reference. |
INIT_AT_KBC |
0 |
Init AT type KB controller. This is only necessary for EMM Homebrew and other projects that use an 8042 keyboard controller instead of PPI. |
INIT_V40 |
0 |
Init V40 config registers (only enable if V40 is installed) |
INT_19_BOOT_HD |
0 |
Try IPL to floppy then hard drive (80h). This is only necessary if Hard Drive BIOS does not implement this behavior (very rare) |
KB_BUF_BDA |
0 |
1=Use start/end keyboard buffer pointers in BDA (40:80-83) (additional code bytes)0=use standard fixed offsets (possible though unlikely compatibility issues) |
KB_FILTER_SC |
0 |
Filter KB make/break code >= 70h for non-standard keyboards that send incompatible key scan codes (ex: Book8088) |
KB_HLT_WAIT |
1 |
Halt (HLT) CPU during KB INT 16h wait for input (see FDC_HLT_WAIT) |
MBR_CHECK |
0 |
Verify magic number of DOS MBR on floppy disk at boot. Enabling can prevent booting disks with no standard MBR ID (AA55H) such as DOS 1.0. |
MUSHROOM_HACK |
0 |
If the user PIT timer is stopped by uncommon software (ex MUSHROOM.COM), enable a workaround that does not require PIT for I/O delays (such as floppy drive operations) |
POST_HD_CHECK |
1 |
Probe POST HD drive geometry and size. See issues with older hard drive controller ROMs. |
RAM_DIGITS |
3 |
Number of zero-padded digits for RAM (3 or 4), if platform supports 1024 KB of detectable memory. |
RAM_TEST_LONG |
1 |
Use normal long RAM test on cold boot. Will speed up cold boot if disabled (recommended only for emulators). |
RAM_TEST_NONE |
0 |
Don't test or clear RAM at all on boot/reboot. Use for development/testing purposes only. |
ROM_SCAN_ALIGN |
1 |
1=Option ROM scan always aligns to 2K boundaries (correct behavior), 0=scan every 2K boundary after previously detected ROM size - if ROM has a non-2K size this can cause subsequent ROMs to be undetectable (incorrect behavior found in many clones) |
SW1_FLP |
4 |
Default max number of floppy drives (if not set by SW1) |
WARM_ENABLE |
1 |
1=enable WARM boot or 0=always COLD boot |
These run your system way out of spec. You have been warned.
| Option | Default | Description |
|---|---|---|
UNSAFE_FLOPPY |
0 |
Reduce floppy drive head settling time for possibly faster seek access and burst transfer reads. |
UNSAFE_REFRESH |
0 |
Use unsafe DRAM refresh timing |
| Option | Default | Description |
|---|---|---|
POST_BANNER |
1 |
show banner and version |
POST_CLS |
0 |
clear screen after POST |
POST_CONFIG |
1 |
show CPU, FPU and ports on POST |
POST_FD_COUNT |
1 |
show floppy drive count on POST |
POST_GLADOS |
0 |
say "Starting GLaDOS..." on boot |
POST_HD_COUNT |
1 |
show hard drive count and params on POST |
POST_THEME |
1 |
color theme for POST screen (see below) |
POST_VID_HGC |
0 |
1=If a Hercules adapter is detected, display "HGC" (can slow down POST if standard MDA is installed)0=Display "MDA" for MDA or Herc |
POST_VIDEO_TYPE |
1 |
show the video adapter type on POST |
POST_WARM_COLD |
1 |
show boot WARM or COLD |
The POST screen colors may be customized in the "Theme My POST Test" section in GLABIOS.ASM.
| Option | Default | Description |
|---|---|---|
POST_CLR_TXT |
CYAN (11) |
Primary text color |
POST_CLR_VAL1 |
GREEN (10) |
Highlighted option |
POST_CLR_VAL2 |
YELLOW (14) |
Highlighted option alternate |
POST_CLR_COLS |
BLUE (9) |
COLD color |
POST_CLR_WARM |
DARKRED (4) |
WARM color |
POST_CLR_GB |
GRAY (7) |
BIOS name in bootup screen |