[Coco] Wolfenstein 3-D on a 4.77mhz 8088? So, 6809 port, anyone?

[Steve Bjork]

Yes, you can use the DMA channel for both memory copy and DRAM refresh.  
Remember, you are read & writing to DRAM and that also does a refresh 
too.  When you are done with the copying, let the DMA go back to refresh 
mode with updated pointer and all is good.

That's how we did back in the day.

Steve


On 4/24/2013 6:01 AM, Luis Antoniosi (CoCoDemus) wrote:
>   IIRC the original IBM PC-XT had the DMA channel 0 hooked up for DRAM
> refresh. I think you cannot make mem2mem transfers on it.
>
>
> On Wed, Apr 24, 2013 at 9:53 AM, L. Curtis Boyle <curtisboyle at sasktel.net>wrote:
>
>> I don't know if it would be completely impossible. While the 8088 PC's did
>> have DMA and hardware divide, their instruction set (especially with memory
>> accesses) could be quite a bit slower than a 6809 (or especially a 6309).
>> Also, note that in that demo, they were using a Sound Blaster for the
>> sound, which would mean a lot less CPU overhead then trying to do it with
>> just the 6809. And, lastly, they are using a very small viewing window (to
>> even get it to the speed that they do have), which appears to be about 1/3
>> the horizontal resolution, and 1/4 the vertical resolution. Since
>> Wolfenstein was a 320x200 game, that would mean about 106x50 resolution
>> (for the actual 3D rendering).
>> And, finally, some proof that this has already been done (graphically as a
>> demo, anyways):
>> http://www.youtube.com/watch?v=W-Ba2X_AZrI
>>
>>
>> L. Curtis Boyle
>> curtisboyle at sasktel.net
>>
>>