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Re: recent topcat(4) framebuffer improvements

Hi Izumi
Thank you for doing this. The ,medium, resolution video cards do indeed use a Topcat with 0.5 Mb of memory, organised into 1024 pixels x 512 lines. 400 lines are displayed and the remaining 112 lines are used for off-screen storage, including the font maps. These cards were intended to drive low-cost monitors which were not fast enough for 1024 horizontal pixels. Therefore, double pixels were used in the horizontal direction, giving a 512 x 400 pixel display. However, single pixels were also allowed if separated by three or more blank pixels and this wasused in the font maps. In case you haven't seen them, there are very useful documents here: https://bitsavers.org/pdf/hp/9000_300/specs/
Best regards

On Sun, 12 May 2024 at 17:41, Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost> wrote:

As noted in src/doc/CHANGES, I've committed several fixes
for NetBSD/hp300 topcat(4) framebuffers, including
HP98542 (untested), HP98543, HP98544, HP98547, and HP98549 etc.


>>      hp300: Fix a wrong palette color setting problems on HP98543 4 bpp
>>              topcat(4) framebuffer on HP360. [tsutsui 20240501]
>>      hp300: Fix "garbage pixels" problems on scrolling ops etc. on
>>              HP98543 and HP98547 topcat(4) color framebuffers.
>>              [tsutsui 20240501]
>>      hp300: Treat HP98542 and HP98543 1024x400 framebuffers as
>>              "pseudo doubled" 512x400 bitmap pixels as HP-UX did, because
>>              even modern LCDs cannot handle such 1024x400 resolutions
>>              properly. [tsutsui 20240501]


Back in 2020, I committed a fix for 98543 (and 98542) to handle
"512x400" pixel framebuffers, but now it turns out that 98542 and
98543 actually have 1024x400 pixels.

Ancient CRTs (and even modern LCDs) cannot handle such resolutions
(modern LCDs assume only upte 720 pixels on 400 line mode) and the
HP manuals also says "512 doubled pixels by 400 scan lines".

(Note MAME's hp9k360 98543 emulation also renders it as 1024x400)

Now NetBSD's topcat(4) driver renders wscons fonts as "doubled pixels"
on 98542 and 98543 so we can see proper glyphs on the real screen,
but we have to consider how X.org server should handle 1024x400 mode.

Anyway I've tested 98543, 98544, 98547, and 98549 on 360, 370, and
380 and all of them shows proper wscons screens, and here is a video
running NetBSD/hp300 -current on HP 9000/360 + 98543:

I've also sent a pullup request of there fixes to netbsd-10
so the next NetBSD/hp300 10.1 will include these improvements.

Have fun,
Izumi Tsutsui

J P Martin Trusler
Email: martin.trusler%gmail.com@localhost
Tel: +44 (0)7734 590826

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