-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Fri, 1 Aug 2003, Daron Edie wrote: > why only 8 bit colour depth? I did a search on the news group archives > and discovered that is all the card is capable of but was it a design > decision on HP's part?
That's right. In the early 1990's when HP was developing the 712 model as a cheap entry level desktop engineering workstation, video RAM was fairly expensive, and 24bit color was considered only for high end machines. The commodity PC market was still sitting at 8 or 16 bpp. To allow reasonable color reproduction with only an 8 bit frame buffer, HP implemented a process called "color recovery," essentially hardware color dithering and lowpass filtering of the chroma signal to a [EMAIL PROTECTED] screen so that an 8bpp framebuffer could as good as a 24bpp framebuffer. HP patented the "color recovery" process, and never released the design of the Visualize chipset so that non-HP-UX operating systems could use the hardware acceleration and color dithering. If you want good color on your HP Visualize-EG, you need to run HP-UX and HP-UX's X server, and have your applications make specific calls to the HP X server to activate "color recovery". With Debian Linux/XFree86, you get an 8-bit, undithered framebuffer, and no hardware acceleration for even simple stuff like window drags, either! Descriptions of the hardware and algorithms were published in the mid 1990's once the hardware was shipping. A description of the model 712 graphics hardware was published in Paul Martin, "An integrated graphics accelerator for a low-cost multimedia workstation," Hewlett-Packard Journal, April 1995, p. 43. The "color recovery" process was described in Anthony Barkans, "Color recovery: true-color 8-bit interactive graphics", IEEE Computer Graphics and Applications, Jan/Feb 1997, p. 67. Our research group (imaging radar) was solely a HP shop up until a few years ago, mainly due to the floating point performance of the Precision Architecture (PA). Since all radar imaging is pseudo-color anyway, the Visualize-EG graphics cards were fine for desktop use. A few years ago we got some IA32 machines, and 24bit color suddenly became available. In the computer lab, we have a choice of IA32 machines with 24bpp color and fairly slow FPU performance, or PA2.0 machines with 8bpp color and good FPU performance. Students always choose the IA32 machines. For the PA2.0 machines, which are running a mixture of HP-UX 11 and Debian 3.0, they prefer HP-UX, as the desktop is more responsive due to the use of hardware 2D graphics acceleration. - -- Leif Harcke [EMAIL PROTECTED] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE/KoibFW+DB6BX7gwRAl2yAKCawRx66rpqTQAm4xrngCVJb6h2VwCfTbOj HN/W2OeudWmHGTkNpK0QzKQ= =z0So -----END PGP SIGNATURE-----
