DOS Days

Cirrus Logic CL-GD510 / CL-GD520

Known as "Eagle II", the CL-GD510 / CL-GD520 chipset arrived in 1988 as the successor to their first SVGA chipset, the CL-GD410/420. It fixed most of the CGA compatibility issues of its forebear. Some had a faster core clock that ran at 40 MHz while others had the 32 MHz version.

Released 1988
Bus ISA 8-bit
Chipset Cirrus Logic CL-GD510 / 520
Standards MDA, Hercules, CGA, EGA, VGA
Memory 256 KB DRAM (80, 100 or 120ns)
RAMDAC (External)
Part # 456-00xx-01 (CL-GD510), 45-00xx-01 (CL-GD520)
Cards Unitron U3969A-V3, VG-1000, MaxLogic MX675, Morse KP800-16, Arche Technologies VGA-0021A, VIP VGP-II
See Also CL-GD410/420, CL-GD610/620

The CL-GD510 and 520 was an ISA Super VGA chipset, called "Eagle II". This chipset was known for its 100% hardware CGA emulation. Most cards that bore this chipset came with both 9-pin and 15-pin D-SUB sockets to support pre-VGA monitors and VGA/SVGA/Multisync monitors. The core was typically clocked at 40 MHz, as was the memory.

Given this was a two-chip chipset, each had these functions:

  • CL-GD510: graphics controller (contains the bus interface logic and is responsible for directing memory reads and writes to and from video memory) and attribute controller (works with the sequencer to generate the correct colour index)
  • CL-GD520: sequencer (responsible for converting video memory to colour indexes - operates in both text and graphics modes) and CRT controller (sends the image data to the monitor)

I have two cards with this chipset - the first is an almost full-length 8-bit ISA card that runs the Eagle II VGA chipset. I dumped the VGA BIOS v2.12 here (the file is 64 KB but I believe the Eagle II is just in the first 32 KB so you will need to edit the file to make it work for re-burning if you use a 32 KB EPROM - otherwise just use my 64 KB one here if using a 64 KB EPROM).

The second one in my collection that uses the 510/520 is a Unitron U3969A-V3 - also an 8-bit ISA card, though it's shorter - in almost every other way the Unitron is the same as the longer CL card mentioned above with the same Eagle II VGA BIOS.

The Ultimate Oldschool PC Font Resource has this card's incredible font in its collection:

The chipset was paired with a 40 MHz RAMDAC (regardless of the core clock of the chipset you had). Compatible RAMDACs include the Analog Devices ADV476KN50, Brooktree Bt476KP50

The chipset can be found on the following graphics cards:

  • MaxLogic MX675
  • Arche Technologies VGA-0021A
  • VIP VGP-II (no FCC ID)
  • Morse KP800-16 (no FCC ID)
  • VG-1000 (see below) - Award VGA BIOS Download courtesy of Andy Welburn incl. the images below
  • Compaq OEM card (I don't have the FCC ID for this)



The CL-GD510/520 came in two clocks speeds: 32 MHz and 40 MHz - the clock speed is stamped on the chip as part of the part number, e.g. CL-GD510A-32PC B is a 32 MHz chip whereas CL-GD510A-40PC is a 40 MHz one.
The revision of the chip is the last character in the part number, so in the image at the top, the 510 is a Rev.B and the 520 is a Rev.C.

Known video ROM BIOS versions include v2.12 and v3.00.



By 1988, a lot of graphics card manufacturers were producing VGA-compatible cards. Some of the more popular ones include ATI with their VGA Wonder and VGA Wonder+, Genoa Systems' SuperVGA HiRes+, Tseng Labs ET3000, and VideoSeven's VEGA VGA which used this chipset. Hercules were also still producing graphics cards, and this year launched the Hercules InColor Card.


In the Media

"Cirrus Logic Inc. announced last week a chip set for VGA hardware designed to let users keep their current monitors and upgrade to VGA monitors in the future.

The new chip set offers full backward compatibility with all graphics modes, according to Randy Roscoe, marketing manager for PC Graphics at Cirrus Logic Inc. The CL-GD510/520 chip set also includes a number of BIOS implementations to optimize VGA performance on 80286- and 80386-based computers, Roscoe said. Those features will allow board makers and system designers to produce VGA-compatible video boards that take advantage of existing monitors while supporting users who upgrade to VGA-capable monitors, Roscoe said.

The CL-GD510/520 is fully compatible with all VGA, EGA, CGA, PGA and MDA modes and with Hercules monochrome graphics, the company said. Thus, boards developed using the chip set and BIOS can be immediately used with any PC monitor, according to Cirrus Logic.

In addition to the full compatibility with other graphics modes, a special 16-bit BIOS for use on cards using the chip set is designed to provide higher performance than boards that use an 8-bit BIOS. A second BIOS, which can be uploaded into system RAM on 80386-based computers, provides significant increases in performance, since the BIOS operations will then reside in the 80386 machine's 32-bit memory and take advantage of fast processor speeds.

The new chips are not expected to increase the price of VGA graphics boards, Roscoe said. The company is now beginning quantity shipments to a number of board makers and system developers. Video-7, a major user of Cirrus Logic's VGA chips, is expected to announce VGA products using the new chip set soon, Roscoe said."

InfoWorld, 26 Sep 1988


Setting it Up

Most cards with this chipset have eight DIP switches on the backplate. They can be configured as follows:

Switch Meaning Known Settings
1-4 Monitor Type MDA: ON ON ON ON
5 Primary/Secondary Adapter If you have more than one graphics card in your system, this is relevant.

ON: This card is the primary graphics card
OFF: This card is the secondary graphics card
6-8 Configuration Auto: ON ON ON


Operation Manual

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Original Utility Disk

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Eagle VGA Controller Utility v4.01
Panel Option Switcher v1.0
Vscreen v1.06 (inverts the display colours)


Contains Eagle VGA Controller Utility v5.03


More Pictures

Andy Welburn's VG-1000 graphics card

A Morse KP800/16