Olivetti M20

---snip--- Hi For the purpose that I can see that Olivetti used a ROM, I think it was the right choice. For the most part it was related to logical to physical mapping. They used a portion of the physical memory for the video memory. This was a 16K block for B/W but it required up to 3 blocks for color. They could configure for 2, 4 or 8 colors. To do more than one color, required expansion memory cards with parallel to serial registers to send the video information to the video controller chip. The ROM could be quickly setup with jumpers for what ever combination of memory that was needed. This simplifies the need to have additional software to configure the system. They also use the ROM to create windows in memory that had the data memory mapped different than the instruction memory. This allowed the processor to access 128K while staying within a single segment. For applications that ran in non-segmented mode, this allows a better use of memory while taking advantage of the smaller code size of non-segmented code. While both of these could have been done with a MMU, it would have been over kill for a desk top machine. They did make some larger machines with Z8000's. I would guess that because of the type of machine these were, they would be expected to have MMU's. These were called the M30 and M40. I've only seen a picture of the M30. It was a half height rack setup. Dwight _________________________________________________________________ Fixing up the home? Live Search can help http://imagine-windowslive.com/search/kits/default.aspx?kit=improve&loc…