S3 805 color depth mystery \ VOGONS

S3 805 color depth mystery

Topic actions

Post a reply

First post, by Datadrainer

Posted on 2021-09-10, 12:54

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

Hi.
I just upgraded the VRAM from 512 KB to 1MB (max supported by the machine) of an HP Vectra 486/25N. That is 4 chips 256x4 60ns embedded + 4 chips 256x4 60ns socketed. The card is an Elsa VLB with a S3 86C805 embedded into the motherboard. The VRAM is fully detected by the BIOS and Windows 95 is working fine with the latest driver available for this card. The problem is I can access 640x480x16-bit and 800x600x16-bit, but not 640x480x24-bit... Win95 starts in 8-bit compatibility mode and say the video adapter cannot work with this configuration.
I don't think of a problem with a memory chip because it should produce video artifacts and not an error in Windows, but who knows. I also tried the default Win95 driver, but it's the same. I don't think of a driver problem either.
There is little difference in memory usage between 800x600x16-bit and 640x486-24-bit and both should fit in 1024 KB. Do anyone have a clue?
Thanks in advance.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 1 of 9, by aitotat

Posted on 2021-09-10, 14:16

aitotat Offline

Rank Member

Rank: Member
Posts: 389
Joined: 2008-03-13, 09:14
Location: Finland

805 does not support 24bit.

Reply 2 of 9, by Datadrainer

Posted on 2021-09-10, 14:42

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

aitotat wrote on 2021-09-10, 14:16:

805 does not support 24bit.

That explains it. As a VLB card and as boards with 4 MB exists I didn't think about that.
Thank you very much for your answer.

Last edited by Datadrainer on 2021-09-12, 20:26. Edited 1 time in total.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 3 of 9, by kixs

Posted on 2021-09-11, 05:31

kixs Offline

Rank l33t

Rank: l33t
Posts: 3380
Joined: 2013-01-31, 02:08
Location: Slovenia

It depends on the RAMDAC. Some cards had better RAMDAC that supported even 24-bit colors - like Diamond Stealth24.

Requests are also possible... /msg kixs

Reply 4 of 9, by Gmlb256

Posted on 2021-09-11, 15:56

Gmlb256 Offline

Rank l33t

Rank: l33t
Posts: 2170
Joined: 2018-04-11, 15:33

AFAIK, early S3 cards only supported 32-bit color (this is more noticeable if you check the list of VESA resolutions, there may be some exceptions) instead of 24-bit and it's actually for performance reasons due to alignment. If the Diamond Stealth24 RAMDAC supports 24-bit color it should appear at least on their Windows drivers.

Reply 5 of 9, by Datadrainer

Posted on 2021-09-12, 18:50

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

Gmlb256 wrote on 2021-09-11, 15:56:

AFAIK, early S3 cards only supported 32-bit color (this is more noticeable if you check the list of VESA resolutions, there may be some exceptions) instead of 24-bit and it's actually for performance reasons due to alignment. If the Diamond Stealth24 RAMDAC supports 24-bit color it should appear at least on their Windows drivers.

The problem is that Windows 95 (non OSR) I have on the PC lists every modes possible even 640x480x32-bit. It's just that it send an error after a restart. That is why I asked the question first.
So it is a limitation of the machine even if nothing like that is specified on the manual.
The Vectra 486N (pizzabox) where cost reduced workstations, so there is nothing wrong with that. I have some XM of the same era with many more options and a Trio64XX chips with 4 MB and full 32-bit color support.
Regards.

Last edited by Datadrainer on 2021-09-12, 19:14. Edited 1 time in total.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 6 of 9, by Datadrainer

Posted on 2021-09-12, 19:02

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

That said, if the card supports 32-bit it haven't enough memory to unlock it.
I haven't check the VESA modes supported by the card. I have to see that to be fixed.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 7 of 9, by Gmlb256

Posted on 2021-09-12, 19:07

Gmlb256 Offline

Rank l33t

Rank: l33t
Posts: 2170
Joined: 2018-04-11, 15:33

It fails due to 640x480x32 (1,228,000 bytes) requiring 2 MB+, 32-bit color are 4 bytes for each pixel.

Reply 8 of 9, by Datadrainer

Posted on 2021-09-12, 19:21

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

Gmlb256 wrote on 2021-09-12, 19:07:

It fails due to 640x480x32 (1,228,000 bytes) requiring 2 MB+, 32-bit color are 4 bytes for each pixel.

That is what I said previously. But it failed too with 24-bit because it is not supported. So I'm limited to 16-bit on this PC. And that's fine as I want to use it for DOS apps only. But I'll will check the VESA table to see if 32-bit mode is supported by the card just for information. It is possible it isn't. The table is stored in the BIOS of that card and as the max DRAM for the card is 1 MB, maybe HP only added entries for 4/8/16 bit color modes.

Knowing things is great. Understanding things is better. Creating things is even better.

Reply 9 of 9, by Datadrainer

Posted on 2021-09-14, 18:04

Datadrainer Offline

Rank Member

Rank: Member
Posts: 229
Joined: 2019-05-20, 09:01

I checked the VESA table today and indeed, as I was thinking, there is no 32-bit.
Color for graphics mode start from 4-bit to 16-bit, including 8 and 15-bit. That's all. Dispite this, the RAMDAC is a Trident TKD8001 24-bit but even SciTech DisplayDoctor cannot unlock the 24-bit modes.
Just as information. If someone, some day, have the same question for the same machine... Who knows.

Thank you to @kixs and @Gmlb256 for the help 😀

Knowing things is great. Understanding things is better. Creating things is even better.

Go to top of page Go to top of page

Back to Video

Main menu

Common searches