Posted By
MMS
on 2020-11-01
14:11:08
 |  Re: ASCII Art Mandelbrot
Yeah, it is really hard to get the proper solution on an 8 bit machine, as least without a standardized and fast communication bus (like PCI or AGP).
When you have a shared memory between the CPU and video card (and sound card) you can do tricks and reallocate memory address, so you can create fake animations, just by simply changeing character sets or gfx memory address. On the other hand, you loose cycles, like we have badlines, anso C64 has some.
The SAM Coupe ("256KB 8 bit ZX spectrum compatible Amiga killer machine upgradeable to 4MB, 6 channel stereo plus ") is a perfect example, even with a 6 MHz Z80 CPU it was only 15% faster than ZX Spectrum, and had troubles to manage gfx screen upgrade. AFAIK the MSX machines with similar Z80 CPU had more success, had a lot of nice arcade conversions (but GFX wise the first MSX1 series was not so great, but MSX2 was impressive).
If you have separated memory for GFX and sound (like VDC in the C128), you may greatly suffer if you want to load massive data through few registers. Certainly, if you have the fast communication channel (like the VGA or sound cards had even via old PCI connection) you do not feel it, but C128 was sluggish with the VDC in graphics mode.
Actually you can speed up the Amiga 1200 to the double just by addig Fast RAM to the shared Chip RAM. So the answer is that the separated RAM is better, but for that you required a fast internal bus for data transfer for the special ICs.
|
