Award BIOS logo
Award BIOS logo (also known as EPA or AWBM) is a family of image formats associated with Award BIOS firmware. These formats are used by those who wish to change the image shown on the boot screen of certain computers. The default image is usually an "Energy Star" logo.
Contents |
Format
There are at least two main versions of the format, sometimes called "version 1" and "version 2". Additionally, different versions of the BIOS have different restrictions on the size of the image, etc. There is evidence that different BIOS versions may even render the same file differently.
Version 1
Version 1 images are rendered in text mode, by customizing the character graphics. Consequently, each 8×14 cell of pixels can only use two different colors.
There is no identifying signature, but most files begin with 11 06 or 11 09, based on the usual dimensions of the image in cells.
| Name | Type and length | Description |
|---|---|---|
| width | uint8_t (1 byte) | Image width in character cells. Usually 17 (0x11). Each cell is 8 dots (pixels) wide. |
| height | uint8_t | Image height in character cells. Usually 6 or 9. Each cell is 14 dots high. |
| cmap | width × height bytes | An array of foreground-background pairs for each character cell. Cells are stored row-by-row, each row stored left-to-right. The less significant nybble corresponds to the foreground colour. |
| bitmap | width × height × 14 bytes | An array of bitmaps for the character cells, stored in the same order as cmap. Each character cell occupies 14 bytes; each byte corresponds to one row of dots, the first byte being the topmost row, and the most significant bit representing the leftmost dot in a row. Bits set to 1 in this bitmap are displayed with the foreground colour of the cell; bits set to 0 are displayed with the background colour. |
| logo | (3 × 2 - 1) × 14 = 70 bytes | A small (3x2 cells; in pixels, 24x28) monochrome Award Software logo. Stored in the same format as bitmap. The top-left corner of the image is not stored and assumed to be empty. There is no corresponding colour map; the logo is always displayed blue-on-black. |
Version 2
Version 2 files begin with a signature of "AWBM". This is a more typical kind of image format, not based on character graphics. It appears in two variants: "planar 4-bit" and "packed 8-bit".
All values are little-endian.
| Name | Length and type | Description | |
|---|---|---|---|
| 4-bit variant | 8-bit variant | ||
| magic | 4 bytes | Always equal to 'A' 'W' 'B' 'M' (i.e. 41 57 42 4d)
| |
| width | uint16_t | Image width and height in pixels. Common image dimensions include 136x84, 136x126 and 640x480. | |
| height | uint16_t | ||
| data | width + (7 - width mod 8) × height / 2 bytes | width × height bytes | The image data; a series of rows of pixels.
|
| palmagic | 4 bytes | Always equal to 'R' 'G' 'B' ' ' (i.e. 52 47 42 20). The palette data has been observed to be absent in some files in the 4-bit format; in that case, the CGA palette should be assumed.
| |
| paldata | 16 × 3 bytes | 256 × 3 bytes | EGA palette data: an array of triplets of bytes in range 0..63. In the 4-bit variant of the format, the basic colour intensities are normally stored in blue-green-red order, but a few files seem to use red-green-blue order instead (example). In the 8-bit variant, they are stored as red-green-blue. |
