Natami MX gets a First True Enhancement
Posted by Thomas Hirsh:
First true enhancement
For the first time on the MX board it is getting exciting, even for me. Till now I was "only" adapting the LX design to the new board. OK, by doing that I made quite huge progress in stability and usability. The board can now even be operated stand-alone. But this were just all the many mandatory things needed for the completeness of the system itself. But now... I was able (and had the time) to improve, or rather extend ECS. As you (hopefully) know, OCS had a hard wired frame generator. Because of that there were two different Agnus chips, one for NTSC and one for PAL. With ECS this issue was resolved in a quite superior manner. They did not only implement a NTSC/PAL switch but also added a complete set set of frame generation registers. From that on there was no limitation to the screen size anymore. Even the A2024 resolutions (1024x1024) were possible. This was a lot more than a common PC could offer that time (in 1988).
With the ECS frame generator it was even possible to display some VGA screen modes as 640x480. But there was still one limitation. The pixel clock was limited to fixed 28MHz. For the A2024 this was no problem, the refresh rate was set to 10Hz and the monitor itself had a built in frame buffer to display the image content at a much higher frequency. VGA and Multisync monitors had no internal memory. So this technique could not be used and resolutions that high as the A2024 were not possible to display on them. And even the 800x600 resolution needed to be in interlace because of the in comparison low pixel frequency. AGA did increase the color depth and the overall number of colors available, but left the pixel clock unchangeable.
The pixel clock on the Natami is not generated by an external oscillator. It is synthesized by a programmable PLL (Phase Locked Loop). Its frequency can be changed at run time. I now implemented an interface which allows the PLL being accessed through DFF registers. With that I am able to set up a basic screen resolution of 1280x1024 in 60Hz for a functionality test. Not system friendly, just a part of a memory field and mouse pointer. But it actually works. I have known it from the beginning that it is possible and will work, but seeing that the Natami can now match the native resolution of my test TFT is something different! I`ll send a design update to Annika as soon as I can.
And the second good news is that with the new resolution I was able to confirm that the digital portion of DVI is also working.
Chipset Features
(new) Frame generation .......... ECS and variable pixel clock -> UCS SyncZorro Interface ....... preliminary version
Copper .................... fully implemented, with buffered data fetch
Video DMA ................. fully implemented
256 color registers ....... fully implemented
AGA HAM8 .................. fully implemented
Sprites ................... 16bit linebuffer
blitter ................... basic implementation. Block and fill mode only, line to come
Video priority ............ half implemented
Scandoubler ............... fully implemented
Interrupts ................ fully implemented
Paula DMA control ......... fully implemented
Audio out ................. fully implemented
Disk DMA .................. 880k and 1760k, read only
Serial Port Paula UART .... fully implemented
Slow peripheral I/O ....... fully implemented
(Joy/Mouse/Keyb/PRT/DSK/SER)
PC mouse and kbd support .. o
CIAs ...................... fully implemented
Board Features
VGA out (DVI-A) ........... working
(new) DVI out (DVI-D) ........... working PCI ....................... transfer only, arbiter and config missing
IDE ....................... PIO mode 0 working
Compact Flash connector ... o
NEC USB PCI ............... o
RTL 8110 LAN .............. o
Battery-backed up clock.... working
15k Video out (module) .... o
15k Video in (module) ..... o
Audio in .................. o
http://www.natami.net/knowledge.php?b=1¬e=33366&x=14WTG Thomas!!
