Cirrus Logic
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Cirrus Logic (NASDAQ: CRUS) is a fabless semiconductor supplier specializing in analog, mixed-signal, and DSP chips. They are presently headquartered in Austin, Texas. Their audio-processors are found in many home-theater receiver and other set-top box hardware. At one time, Cirrus Logic also designed and sold modem controllers, Hard Disk controller chips, CD-drive controller chips, PC sound-card controllers, PC graphics chips. (Cirrus Logic has ended these business operations.) It was started as Patil Systems, Inc., in Salt Lake City in 1981, by Dr. Suhas Patil and renamed as Cirrus Logic when it moved to Silicon Valley in 1984.
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[edit] Graphics history
In the early 1990s, Cirrus Logic was a leading supplier of low-cost PC graphics chips. Cirrus's Microsoft Windows 2D GUI accelerators (GDI) were among the fastest in the low-end market-segment, outperforming competing VGA-chips from Oak Technologies, Trident Microsystems, and Paradise (Western Digital). For example, the Cirrus GD5422 (1992) supported hardware acceleration for both 8-bit color and 16-bit color. It was one of the lowest-priced SVGA controllers to support both.
By the mid-1990s, when PC's had migrated to the PCI bus, Cirrus had fallen behind S3 and Trident Microsystems. When the announced release date of the GD5470 "Mondello" came and went, Cirrus's reputation in desktop PC-graphics suffered. (Mondello would have been the company's first 3D-accelerator, but instead became vaporware.)
Later, the company was one of three companies to provide a VGA-controller for the 3dfx Voodoo Rush 3D-accelerator card. The chips Cirrus Logic used were derivatives of the Laguna family, with model numbers GD5645 and GD5646. The Voodoo Rush card combined two separate graphics controller chips for legacy-VGA (2D) and 3D functionality. Both chips shared the same framebuffer memory. However, the Voodoo Rush boards were a disappointment because the 2D chip was inferior to many cards of the time, and its 3D was slower than that of the older and separate Voodoo Graphics board.
The company's final graphics chips, the GD546x "Laguna" series of PCI/AGP 3D-accelerators, were novel in that they were one of the few video cards to use Rambus RDRAM. However, like many other 2D/3D chips at the time, the feature set of perspective-correct texture mapping, bilinear filtering, single-pass lighting, gouraud shading, and alpha blending, was both slow and incomplete.
[edit] Graphics chipsets
- DESKTOP
- CL-GD5420 - ISA SVGA chipset, highly integrated (RAMDAC + PLL), 1 Mbyte.
- CL-GD5422 - Enhanced version of the 5420 (32-bit internal memory interface, hardware BITBLT. An ISA video card carrying this chipset offered 1280x1024 interlaced max resolution[1]).
- CL-GD5424 - VLB version of the 5422, but resembles the 5426 in some respects.
- CL-GD5426 - ISA bus and VLB up to 2 MBytes of memory.
- CL-GD5428 - Enhanced version of the 5426. Faster BITBLT engine. [2]
- CL-GD5429 - Enhanced version of the 5428; supports higher memory clock and has memory-mapped I/O.
- CL-GD5430 - Similar to 5429, but with 543x core (32-bit host interface).
- CL-GD5434 - Alpine family chip with 64-bit internal memory interface. Only supports 64-bit mode if equipped with 2 Mbytes of video memory; commonly equipped with 1 Mbytes, extendable to 2 Mbytes.
- CL-GD5436 - Highly optimized 5434.
- CL-GD5440 - Similar to the CL-GD5430. (GD54M40 has motion-video acceleration.)
- CL-GD5446 - Another member of the Alpine family of 2D accelerators; adds motion-video acceleration to the CL-GD5436.
- CL-GD546X - The Laguna VisualMedia family of 3D accelerators '64,'65 (PCI, AGP). These chips use Rambus RDRAM memory. The '62 is a 64-bit 2D accelerator, including a BitBLT engine, video windows, and 64x64 HW cursor.
MOBILE
- CL-GD6420/6440 Used in some laptops, similar to older Cirrus chipsets (5410/AVGA2).
- CL-GD6205/6215/6225/6235 - Compatible with the 5420.
- CL-GD7541/7542/7543/7548 - Compatible with the 5428/3x.
