Saturday, September 27th, 2014

Time	Event
3:36p	NVIDIA Begins Requiring Signed GPU Firmware Images An anonymous reader writes: In a blow to those working on open-source drivers, soft-mods for enhancing graphics cards, and the Chinese knock-offs of graphics cards, NVIDIA has begun signing and validating GPU firmware images. With the latest-generation Maxwell GPUs, not all engine functionality is being exposed unless the hardware detects the firmware image was signed by NVIDIA. This is a setback to the open-source Nouveau Linux graphics driver but they're working towards a solution where NVIDIA can provide signed, closed-source firmware images to the driver project for redistribution. Initially the lack of a signed firmware image will prevent some thermal-related bits from being programmed but with future hardware the list of requirements is expected to rise. Read more of this story at Slashdot. (Comment on this)
6:46p	Why the Z-80's Data Pins Are Scrambled An anonymous reader writes "The Z-80 microprocessor has been around since 1976, and it was used in many computers at the beginning of the PC revolution. (For example, the TRS-80, Commodore 128, and ZX Spectrum.) Ken Shirriff has been working on reverse engineering the Z-80, and one of the things he noticed is that the data pins coming out of the chip are in seemingly random order: 4, 3, 5, 6, 2, 7, 0, 1. (And a +5V pin is stuck in the middle.) After careful study, he's come up with an explanation for this seemingly odd design. "The motivation behind splitting the data bus is to allow the chip to perform activities in parallel. For instance an instruction can be read from the data pins into the instruction logic at the same time that data is being copied between the ALU and registers. [B]ecause the Z-80 splits the data bus into multiple segments, only four data lines run to the lower right corner of the chip. And because the Z-80 was very tight for space, running additional lines would be undesirable. Next, the BIT instructions use instruction bits 3, 4, and 5 to select a particular bit. This was motivated by the instruction structure the Z-80 inherited from the 8080. Finally, the Z-80's ALU requires direct access to instruction bits 3, 4, and 5 to select the particular data bit. Putting these factors together, data pins 3, 4, and 5 are constrained to be in the lower right corner of the chip next to the ALU. This forces the data pins to be out of sequence, and that's why the Z-80 has out-of-order data pins." Read more of this story at Slashdot. (Comment on this)
7:51p	From the Maker of Arduboy: Tetris On a Bracelet timothy writes: Kevin Bates showed off his tiny ("credit card sized") homebrewed game-playing rig at OSCON this summer. Not content with merely wallet sized, he's now squeezed enough display — three of them, lacking a curved display to wrap around the wrist — input sensors, and processing power (Atmega 328p) to play Tetris on a tiny, multi-segmented bracelet (video). Sure, there's been Tetris on watches before, but from large-budget companies, not — at least not that I've ever seen — from hackers. Bates' post gives some more technical details, too. Read more of this story at Slashdot. (Comment on this)

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