Announcement: 'libcpu' Binary Translator
I just did a Lightning Talk at the 26th Chaos Communication Congress 26C3 about our new project “libcpu”, and it has already been picked up by Golem.de and reddit.com, so I might as well announce it here:
Having Fun with Branch Delay Slots
Branch Delay Slots are one of the awkward features of RISC architectures. RISC CPUs are pipelined by definition, so while the current instruction is in execution, the following instruction(s) will be in the pipeline already. If there is for example a conditional branch in the instruction stream, the CPU cannot know whether the next instruction is the one following the branch or the instruction at the target location until it has evaluated the branch. This would cause a bubble in the pipeline; therefore some RISC architectures have a branch delay slot: The instruction after the branch will always be executed, no matter whether the branch is taken or not.
PCEPTPDPTE
Here is a new pagetable entry.
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.
Pictures of Apple Lisa 2 Boards
The Apple Lisa is a quite rare collector’s item today. So if you hold one in your hands, you better take some high resolution pictures of the boards. Here they are:
TI-99/4A BASIC as a Scripting Language
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.
Amiga intern (PDF)
(German) Die Qualität dieses Scans ist furchtbar, aber wenigstens ist die PDF durchsuchbar.
Dangerous Xbox 360 Update Killing Homebrew
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.
Minimizing the Assembly needed for Machine Initialization
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.
Aggressive Tail Call Optimization
In some i386/x86_64 assembly code my coworker was working on, there was a macro like this:
LOAD"$",8
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.
The Infinite Loop Mystery
Today’s puzzle is about some code behaving horribly wrong.
This is Copyright 1983 Microsoft – NOT!
If you look at a hexdump of any version of the Logitech mouse driver for MS-DOS, you will see the following:
The Giant Pile of Money in My Office
Corporate security thought it wasn’t the best idea:
Apple Copland Reference Documentation
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”.
Readable and Maintainable Bitfields in C
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.
A Lot of Security
I happened to drive through Cupertino, CA, USA last Wednesday and ended up in this situation:
Stamp Vending Machine DoS
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:
Feed in Rogue Signal Here
Sometimes it makes sense to label a surveillance camera.
Apple Lisa Operating System Reference Manual (PDF, 1983)
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.