rcd@ico.isc.com (Dick Dunn) (04/26/91)
davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes: > I have been waiting for frame buffers to come out with an option to > map the whole thing in extended memory, say between 15-16MB. I predicted > this as a popular enhancement when EGA first came out, and I was wrong. > I find it hard to belive that no one has done this,... Cornerstone has done this. It's much more pleasant than having to mess around with switching "page registers" or "bank registers" or whatever every handful of scan lines. (Nice displays, too.) However, mapping into extended memory is a problem these days, because people are pushing the amount of memory they put into PCish machines. A card sitting on the ISA bus has to map somewhere between 2 and 16 Mb, and you may also be restricted to not using the last Mb. The Cornerstone cards, as an example, use a 2 Mb space and decode the uppermost 3 bits of the 24-bit address. On many systems, that means you have to put them at 12-14 Mb, so your max physical memory is 12 Mb. (I'm omitting a lot of unpleasant details here.) Folks want more memory than that. Maybe EISA machines, with the additional address space, will give enough people enough courage to go for video frame-buffer devices in PCland. -- Dick Dunn rcd@ico.isc.com -or- ico!rcd Boulder, CO (303)449-2870 ...While you were reading this, Motif grew by another kilobyte.