Michael J. Mahon wrote:
David Schmenk wrote:David Empson wrote:jsnospam@cimmeri.com <js@cimmeri.com> wrote:On Feb 27, 7:31 am, demp...@actrix.gen.nz (David Empson) wrote:The horizontal line is the same width in SHR and other video modes,implying the same time (about 40 microseconds) for the active portion ofthe row, so it must have a higher frequency dot clock in order to fit 320 or 640 pixels in the same space as 280 or 560 for other modes.David, have you actually verified that they are the same width with your eyeballs and a ruler? Just curious if this is an established fact now.Yes, I just checked. If anything, SHR mode is a fraction narrower (about 2 mm) than text mode, and the entire screen offset to the left about 2 mm. These are probably artifacts of my old greenscreen composite monitor, depending on how many pixels are illuminated.I have a Monitor /// hooked up to my IIe->IIgs upgrade for that oh-so-retro feel and decided to compare modes. On my Monitor ///, SHR is *wider* than the standard modes, and the left border starts not quite one character width (40 col character, that is) sooner. The right border seems to be identical. I don't see any dissimilar widths in any column. I think this would be pretty obvious, especially on a green screen. I'll pull out a ruler later when I have a little more time.And, yes, GS/OS looks pretty awful on a green screen.There is a problem with measuring the "actual" width of a CRT display, which was alluded to by David. Unless the displays of the two modes have the same average brightness, or unless the HV supply of the monitor is well-regulated, when modes change the HV current drain will also change, resulting in a brighter picture appearing wider than a darker one. This weakness peculiar to CRT displays is called "blooming", and is the result of the electron beam being more easily deflected when accelerated by a lower voltage. -michael NadaNet networking for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."
Curse these ancient analog devices. Yes, as soon as I sent that message, I fiddled with the brightness control and everything shifted. Going back and checking with a close facsimile of the GS/OS desktop (mousedesk in DHR) results in a similar shift to the left that David saw.
Dave...