VOGONS


CGA/MDA style CRTCs

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First post, by Jo22

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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.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 2 of 3, by Jo22

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Thank your a lot for replying Scali. 😀 I came across the HD46505 when I checked the chips inside my PC/XT clone, a Nixdorf M35.
Since I didn't know what this chip was doing, I searched the web and finally found this information on a Japanese homepage.
I wonder, though, if Hitachi made that chip on its own will or because they got an explicit order from Motorola to invent one for their 6800 line..
Anyway, these cards of yours sound interesting, too. I'd love to see one or two pics of them some time. 😀

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 3, by Scali

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Jo22 wrote:
Thank your a lot for replying Scali. :) I came across the HD46505 when I checked the chips inside my PC/XT clone, a Nixdorf M35. […]
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Thank your a lot for replying Scali. 😀 I came across the HD46505 when I checked the chips inside my PC/XT clone, a Nixdorf M35.
Since I didn't know what this chip was doing, I searched the web and finally found this information on a Japanese homepage.
I wonder, though, if Hitachi made that chip on its own will or because they got an explicit order from Motorola to invent one for their 6800 line..
Anyway, these cards of yours sound interesting, too. I'd love to see one or two pics of them some time. 😀

Well, there's a great picture of a Hercules card with a Hitachi chip on Wikipedia:
https://en.wikipedia.org/wiki/Hercules_Graphi … ercules_HGC.png
Apparently it is marked both as HD6846SP and HD46505SP.

My own CGA card has an MC6845, but I know there was someone who tested the party version of 8088 MPH on a real IBM CGA card, with a HD6845, which is how we found out about the incompatibility. We later found out that later revisions of the MC6845 also had this other behaviour. So perhaps the Motorola chip was the incompatible one in the first place 😀
The card on minuszerodegrees is one as well: http://minuszerodegrees.net/5150_5160/cards/ibm_cga.jpg
Here is also an IBM MDA card with HD6845: http://www.vgamuseum.info/images/palcal/hitac … _mda_top_hq.jpg

http://scalibq.wordpress.com/just-keeping-it- … ro-programming/