First post, by Jo22
- Rank
- l33t++
Hi everyone, just found out that the popular 6845 apparently was based on the HD46505 design by Hitachi (datasheet).
Furthermore, there also was a "sucessor" (kind of; among many enhanced clones), the MB89321A by Fujitsu (datasheet)..
http://www.st.rim.or.jp/~nkomatsu/crtif/HD46505.html
English Translation
The (auto-translated) Wikipedia entry below describes the MB89321A as
"MC6845 upper compatible, CMOS version CRTC. 6800 series interface.
Scan mode can be interlaced, non-interlaced, non-interlaced and video configurable
Vertical blanking / light pen interrupt function
Independent paging / scrolling of 4-split screen
Simultaneous smooth scroll function up to 4 screens
External synchronization, superimposed display with TV broadcast, synchronization with other CRTC"
Anyway, just thought I should share that bit of information.
There sure is more to it, but that's what I found so far (so it's not a complete story). 😅
Of course, there used to be other 6845 semi-compatible chips or chips of comparable feature sets in the (far) east.
The µPD7220, for example, what was used in Japan on PC-9800 series and
as the U82720 in the eastern block (EC-1834 PCs, for example).
Though strictly speaking, these are GDCs (Graphics Display Controllers) rather than CRTCs.
Another interesting chip was the HD63484, apparently, an ACRTC (Advanced CRTC).
"There are 23 graphic drawing functions such as circle and paint on the on-chip,
and functions such as overlay display, zoom and scroll.
The data bus width is 8/16 bit and used for 68 / 68K series."
A list is also available at Wikipedia Japan.
https://ja.wikipedia.org/wiki/CRTC_(LSI)
English Translation
Edit: Text fixed.
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