A Standalone printf() for Early Bootup
A while ago, I complained about operating systems with overly complicated startup code that spends too much time in assembly and does hot have printf() or framebuffer access until very late.
Some Assembly Required
A while ago, I complained about operating systems with overly complicated startup code that spends too much time in assembly and does hot have printf() or framebuffer access until very late.
It is a good time for statically recompiled versions of BASIC from old computers. First there was Apple I BASIC. Then came Commodore BASIC. Now, due to overwhelming demand, we’re proud to release TI-99/4A BASIC. For those unfamiliar the TI-99/4A was a home computer by Texas Instruments released in 1981. Unusually for the time it had a 16-bit CPU: the TMS9900.
(German) Die Qualität dieses Scans ist furchtbar, aber wenigstens ist die PDF durchsuchbar.
On Tuesday, Microsoft has released an Xbox 360 software update that overwrites the first stage bootloader of the system. Although there have been numerous software updates for Microsoft’s gaming console in the past, this is the first one to overwrite the vital boot block. Any failure while updating this will break the Xbox 360 beyond repair. Statistics from other systems have shown that about one in a thousand bootloader updates goes wrong, and unless Microsoft has a novel solution to this problem, this puts tens of thousands of Xboxes at risk.
In many operating systems, I have seen overly complicated startup code. Too much is done in assembly, and printf() and framebuffer access is only available very late. In the next three blog posts, I will show how this can be avoided.
In some i386/x86_64 assembly code my coworker was working on, there was a macro like this:
Commodore computers up to BASIC 2.0 (like the Commodore 64, the VIC-20 and the PET 2001) only had a very basic understanding of mass storage: There were physical device numbers that were mapped to the different busses, and the “KERNAL” library had “open”, “read”, “write” and “close” functions that worked on these devices. There were also higher-level “load” and “save” functions that could load and save arbitrary regions of memory: The first two bytes of the file would be the (little endian) start address of the memory block.
Today’s puzzle is about some code behaving horribly wrong.
If you look at a hexdump of any version of the Logitech mouse driver for MS-DOS, you will see the following:
Corporate security thought it wasn’t the best idea:
The Copland project was Apple’s ill-fated attempt in the mid 1990s to replace the aging classic Mac OS with a more modern operating system that had a microkernel, virtual memory and preemptive multitasking. Information on Copland is scarce, therefore I have compiled 20 hard to find Copland reference documents, as well as the 359 page book “Mac OS 8 Revealed”.
Bitfields are very common in low level C programming. You can use them for efficient storage of a data structure with lots of flags, or to pass a set of flags between functions. Let us look at the different ways of doing this.
It makes sense for a stamp vending machine to have some limits and not print any amount of stamps or stamps of any value. The vending machines from the Deutsche Post are a little weird though:
Sometimes it makes sense to label a surveillance camera.
The Apple Lisa from 1983 was the first consumer-class computer with a graphical user interface and significantly more advanced than the 1984 Macintosh, which had a similar UI, but a comparatively primitive underlying OS. Here, I present a searchable PDF of the rare “Operating System Reference Manual for the Lisa” (1983), as well as a quick overview of the OS and how it compares to UNIX.
The core of the Amiga Operating systems consists of the three major components Exec (scheduling, memory management, IPC), Intuition (GUI library) and AmigaDOS (process and file management). AmigaDOS is based on the Tripos operating system which Commodore bought because development of their own DOS subsystem failed to meet deadlines. In this article, I am presenting searchable PDFs of the very rare Tripos manuals (638 pages) as well as the AmigaDOS manual (304 pages). Comparing the two documents will share some insight in the relationship between Tripos and Amiga OS.
Update: The source is available at github.com/mist64/msdos1
Update: The source is available at github.com/mist64/msdos1