Answer by cjs for When did the PC bus start slowing access to video RAM?
This question starts with a number of misconceptions about early video,memory and bus systems that need to be addressed in order to clarify whatthis question really appears to be about.If you want the...
View ArticleAnswer by supercat for When did the PC bus start slowing access to video RAM?
The original CGA always imposed wait states on display memory accesses. The card's memory subsystem always performs one access every four pixel clocks, and only half of those are available to the CPU...
View ArticleAnswer by Raffzahn for When did the PC bus start slowing access to video RAM?
TL;DR: When the CPU-bus became faster than the I/O-busNow, there are always going to be wait states during active scan line, because the video chip is using some of the video memory bandwidth for...
View ArticleWhen did the PC bus start slowing access to video RAM?
The PC architecture, from the original IBM PC onward, has always been designed around the idea that video memory will be on an expansion card. This was an unusual design decision; most 80s computers...
View ArticleAnswer by David G. for When did the PC bus start slowing access to video RAM?
Actually, if you carefully read the BIOS for the IBM PC and CGA video (I did), you will find that (at least in text mode) it delayed every access to the video memory until the display entered a...
View ArticleAnswer by davolfman for When did the PC bus start slowing access to video RAM?
In many ways it's not that the PC architecture has slow access to video RAM. It's that, thanks to a lack of advanced features like sprites and backgrounds, it requires much more access to video RAM....
View Article
