[comp.sys.mac] moving video ram on the IIci

pts@watt.acc.Virginia.EDU (Paul T. Shannon) (10/07/89)

In the October Byte review of the IIci, page 104, it says:

   'a section of ordinary system RAM, rather than video RAM on a NuBus
    board, is used for the video frame buffer.  The 68030 can put
    video information directly into memory at full speed...'

My question:  can the video hardware be told to look at _different_
addresses in system RAM when it goes to refresh the screen?  For example,
can I load one screen image at address A, another at address B, and
cause them each to be displayed by simply changing the base address
of video ram?  Or, is there just one address in system RAM where the
video hardware always looks?  
 - Paul Shannon
   pts@virginia.edu

noah@Apple.COM (Noah Price) (10/09/89)

In article <986@babbage.acc.virginia.edu> pts@watt.acc.Virginia.EDU (Paul T. Shannon) writes:
>My question:  can the video hardware be told to look at _different_
>addresses in system RAM when it goes to refresh the screen?

Nope, as you say:

> [...] is there just one address in system RAM where the
>video hardware always looks?  

The video hardware always gets its data starting at the base of Bank A
of DRAM.  This is why you must have memory in Bank A in order to use built-in
video.

noah price                                        Mac IIci Hardware Design Team
												  Apple Computer, Inc.
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noah@apple.com                                      ...!{sun,decwrl}!apple!noah