750 Family Device Support in Linux
The bad news is that the 750 is old and slow. The good news is that every device type in the family is supported in Linux. More bad news: Getting those device to work in Linux can be hard.
The 750 family has a few models. I will list their similarities first.
The 750 uses an Intel 80486 running at 33MHz. Desktop CPUs now run 100 times faster. Some models run the CPU at 50MHz on a 25MHz clock. Linux requires an 80386 or better, so we are fine here.
The 750 came with 4MB memory built in and one IC DRAM card slot. It's like PCMCIA, and yet not enough like it to be useful. It has a 64-bit wide memory path that runs at 33MHz for a memory bandwidth of 267MB/s. It can accept a 32MB memory card. Linux will run with this small amount if you are careful.
The 750 uses the ISA bus. This means that the PCMCIA slots are 16-bit or PC Card slots. The memory runs at full CPU speed of 33MHz. The ISA bus runs at (unknown) MHz.
The video controller is the WD 90C24 and the 750 has 1MB video RAM. That's enough for 640x480 at 24 bits per pixel, or 1024x768 at 8 bits per pixel. It has been supported in Linux for some time. However, the chipset and video memory is not detected correctly, meaning hand-tuning of X configuration files is necessary.
Further, the svga driver (which includes this video chip) has not been ported to the most recent versions of X.org or X11R6.
Debian starts X with a display of 320x200 at 8 bpp. 640x480 with 4bpp should be easy and enough for the models without color screens.
There is a VGA connector on the 750 for connecting to an external monitor.
- The 750 and 750P have a 9.5" STN LCD panel with 640x480 pixels. They can display 64 levels of gray and have a contrast ratio of 18:1.
- The 750Cs has a 9.5" DSTN LCD panel with 640x480 pixels. It can display 256 colors and has a contrast ratio of 20:1.
Active Matrix Color
- The 750C has a 10.4" TFT LCD panel with 640x480 pixels. It can display 256 colors and has a contrast ratio of 100:1.
The 750 uses the Crystal Semiconductor CS4248-KL sound chip. That chip works with Linux in other machines. I have not seen it work on the 750. I believe that is because IBM puts the chip in IO address space that is not normally used in Linux.
The chip can reside at 0x0030, 0x4E30, 0x8E30 or 0xCE30. The last time I tried to pass in the address to the Linux sound driver, it didn't work.
The 750 uses a PCMCIA controller that is well supported in Linux. Nothing special is required to get PC Cards working. Note that only 16-bit cards will work. 32-bit or CardBus cards will not fit in the slots without force and will not work if forced.
The 750 uses Nickel Metal Hydride batteries. APM might work. Edit me.
The 750 family came with either a 170MB or 340MB hard drive. Each drive was 17mm think and resided in a caddy that was difficult to disassemble.
The connector shorts pins 1 and 2 so that modern hard drives configure themselves to be the slave drive when they are plugged in. This stops most operating systems from installing correctly. To get newer drives to work, you can either bend or break the pin on the drive. Since laptop drives are usually the only drive in a system, this may not be as bad as it sounds. Instead, you can scrape a trace on the connector in the caddy or on the system board. This means that the older drives will no longer work in the machine.
Linux supports the EPP parallel port fully.
The 16440-based serial port will also work but is a really awful device and may not keep up with modern serial devices.
The PS/2 port supports mice and keyboards with adaptors.
The 750 has no infrared or USB ports.