DOS Days

Cirrus Logic CL-GD5426

The CL-GD5426 was a Super VGA chipset released in 1993. It was designed to work on the ISA or VESA Local Bus and allowed for up to 2 MB of video memory to be accessed. It was Cirrus Logic's first GUI accelerator chipset, having a 32-bit hardware BitBLT (bit block transfer) engine.

	Released	March 1993
	Bus	ISA 16-bit or VESA Local Bus
	Chipset	Cirrus Logic CL-GD5426
	Standards	MDA, Hercules, CGA, EGA, VGA
	Memory	256 KB, 512 KB, 1 MB or 2 MB FPM DRAM (70, 80 or 100ns)
	RAMDAC	(Internal)
	Part #	-
	FCC IDs
	Cards
	See Also	CL-GD5422/4/5, CL-GD5428

The core clock on the 5426 ran at the same speed as the 5422/5424 running at 80 MHz with memory clocking in at 50 MHz. The maximum resolution supported by the chipset was 1280 x 1024 (interlaced) in 256 colours. If a higher colour depth was needed, you could run a 2 MB card in 1024 x 768 at 64,000 colours or 640 x 480 in 16.7-million True Color. For the fastest refresh rate of 72 Hz non-interlaced, the chipset could be run in 1024 x 768 or 800 x 600 resolution.

Memory-wise, the chipset was backward-compatible with earlier 542x chipsets, though almost every card that used the CL-GD5426 came with either 1 MB or 2 MB of memory. These were oriented in two banks of 1 MB Fast Page Mode (FPM) DRAM. One exception to this was BOCA Research's SuperX VGA which came in three variants - the cheapest of these was a 512 KB version that was not expandable.

The chipset was extremely popular, and can be found on the following SVGA cards:

Diamond SpeedSTAR Pro ISA (FCC ID: FTUISA5426A)
Genoa Systems Windows VGA 24 Model 8500/VL
Hightech Information System (HK) Ltd (FCC ID: KBIA3U5428)
ASUS GMIO-470
Octek VL-COMBO (Part no. EP40084R32)
Boca Research SuperX Accelerator VGA
Cardinal Technologies VideoSpectrum XL
Edge Technology D24 BitBlaster Plus (Edge Technology became Micron Computer, Inc. in 1993)
DTK PTI-240A VESA VGA (FCC ID: F825K4PTI240)
RT-3501-1 (FCC ID: I4L3405)
Pine PT-2036 (FCC ID: H52-PT-2036)
Octek AVGA-26 (Part no. EP20073R11)
Octek(?) AVGA-3VL (Part no. MVGA-AVGA3VL)
RL-3503-2
Cirrus Logic (FCC ID: J6N4LVLDM7)
Pine PTI-5426-VL (FCC ID: PTI 5426VL)
Whole In One
Aquarius Systems Inc (FCC ID: GPLAPC-5426)
Magitronic (FCC ID: JDF-VGA-VL5426)
FIC (First International Computer) FCC ID EUNVGA-542V
ASL Lightning2 / Alpha Systems Lab (FCC ID: JSQASLWACJJMP)

Here is a summary of the Cirrus Logic CL-GD542x range so you can compare each chipset's differences from one another:

	5420	5421	5422	5424	5425	5426	5428	5429
Bus	ISA	ISA	ISA	VLB	VLB	VLB	VLB	VLB
GUI Acceleration	-	-	-	-	-	BitBLT	Enhanced BitBLT	MM I/O
Max. Video Memory	1 MB	1 MB	1 MB	1 MB	1 MB	2 MB	2 MB	2 MB
Memory Bus Width	16-bit	16-bit	32-bit	32-bit	32-bit	32-bit	32-bit	32-bit
Core Clock Frequency	75 MHz	75 MHz	80 MHz	80 MHz	80 MHz	80 MHz	80 MHz	86 MHz
Memory Clock Frequency	50 MHz	50 MHz	50 MHz	50 MHz	60 MHz	50 MHz	50 MHz	60 MHz
Max. Resolution at 256 Colours	1024 x 768 (NI)	1024 x 768 (NI)	1024 x 768 (NI)	1024 x 768 (NI)	1024 x 768 (NI)	1280 x 1024	1280 x 1024	1280 x 1024

Revisions

The chipset itself came in these revisions: A.

Competition

In direct competition with the CL-GD5426 chipset were the S3 86C801 (cards including the Orchid Fahrenheit VA, Mirage Storm 1280/256, VideoSeven Win.PRO and Actix GraphicsEngine 32 Plus) and ATi Mach32 (cards including the ATI Graphics Ultra Plus and ATI Graphics Ultra Pro). There were much higher-priced cards available that were typically purchased for professional use, such as CAD applications. These could get you up to 1600 x 1200 resolution (in 16 colours). There were also chipsets coming out that supported up to 4 MB of VRAM such as those based on S3's 86C928 chipset. Some mid-range options also existed, such as the Hercules Graphite Card which used an IIT AGX-014 accelerator coprocessor.

PC Magazine's GUI accelerator card round-up in April 1993 determined that cards based on the CL-GD5426 were best-performing under real DOS, as their Windows performance wasn't great compared to the S3 86C801.

In the Media

"Cirrus Logic, well-known for its GD5422 dumb frame buffer chip used in boards such as Sigma Designs' WinStorm and STB Systems' Evolution VGA, enters the video acceleration market with the Cirrus Logic GD5426. But the GL5426 sticks close by Cirrus Logic's frame buffer roots by performing best in DOS video modes.

The GD5426 doubles the Graphics Winmark performance of its non-accelerated sibling at some resolutions and color depth, but the problem is that the GD5426 still lags behind when measured against Windows performance of much of the accelerator competition.

The GD5426 boards we tested managed only 4.04 to 4.14 megapixels per second in 16-color Super VGA and 4.41 to 4.60 in 16-color 1,024-by-768 mode tests, for example, while [S3] 86C801- and 86C928-based products racked up average scores of 10 megapixels per second in these modes. (Even the 86C924 chip outdid the GD5426: the boards using that chip scored around 7 megapixels per second).

At 256 colors in Super VGA and 1,024-by-768 resolutions, the GD5426-based cards scored close to or a little better than 8 megapixels per second, but those scores still did not come close to those achieved by most of the 86C801-based or 86C928-based competition (which scored around 12 to 14 megapixels per second).

All the GD5426 boards we saw used a 16-bit ISA hot bus interface. According to Cirrus Logic, the chip itself delivers 32-bit access to display memory and also has a 32-bit internal data path for Extended Industry Standard Architecture (EISA) or local-bus solutions. Part of the reason GD5426-based boards can't keep up is that the chip accelerates only BitBlts, image transfers and raster operations. And while the company says that the chip provides for font caching, none of the boards we tested for this review supported that feature." PC Magazine, April 1993