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SVGA minimum RAM?

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First post, by ntalaec

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Does anyone know what is the minimum video RAM required for 640x480 256 colors?

It is possible with 256 KB or 512 KB is required?

Reply 2 of 21, by ntalaec

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Yes, but according to this :

https://web.archive.org/web/20190908005630/ht … her-resolutions

This article describes the memory requirements for different video resolutions in Windows.

Colors 16 256 32K*** 64K*** 16.7 Million***
--------------------------------------------------------------------
Resolution
640x480 256K* 256K 1 MB 1 MB 1 MB
800x600 256K 512K 1 MB 1 MB 1.5 MB
1024x768 512K 1 MB 1.5 MB 1.5 MB 2.5 MB
1280x1024 1 MB** 1.5 MB 2.5 MB 2.5 MB 4 MB

* Most VGA cards are shipped with 256 KB of RAM installed.
** 640 KB actually needed. 1 MB required due to upgrade requirements on video cards.
*** External RAMDAC (RAM digital-to-analog converter) required for these colors.

Was also possible with 256 KB. It was only possible in Windows?

Reply 3 of 21, by rmay635703

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I had a 256kb SVGA video card

800x600x16 was possible
Also had a windows driver for 640x400x256 which I’m told is abit odd.

Always wondered why more cards didn’t support that out of the box?

Reply 5 of 21, by dionb

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ntalaec wrote on 2020-03-08, 20:08:

Yes, but according to this :
[...]

Was also possible with 256 KB. It was only possible in Windows?

Yes, if they found some magical way to compress the information... except they didn't, so the calculation still holds:
640x480x8 = 2457600b = 307200B = 300kB

300kB > 256kB, so can't be done. You need 512kB.

Reply 7 of 21, by Jo22

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rmay635703 wrote on 2020-03-08, 20:13:
I had a 256kb SVGA video card […]
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I had a 256kb SVGA video card

800x600x16 was possible
Also had a windows driver for 640x400x256 which I’m told is abit odd.

Always wondered why more cards didn’t support that out of the box?

I confirm this. The Paradise PVGA1A driver for Windows 2.x does support this, for example.
I've sucessfully tested this this on both emulated and real hardware with 256kiB of Video RAM.

640x400x256c is also the lowest VESA VBE mode.

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Reply 8 of 21, by Grzyb

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rmay635703 wrote on 2020-03-08, 20:13:
I had a 256kb SVGA video card […]
Show full quote

I had a 256kb SVGA video card

800x600x16 was possible
Also had a windows driver for 640x400x256 which I’m told is abit odd.

Always wondered why more cards didn’t support that out of the box?

Actually, many SVGA cards do support 640x400x256, via built-in BIOS mode.
Even more can be made to support it with appropriate software, ie. UniVBE/SDD

However, it's true that few cards came with Windows drivers for that mode.
And the reason was: Windows 3.x was designed primarily for 640x480 or higher.

Reply 9 of 21, by elianda

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The OPs question is a bit misleading.

What Super VGA means was never really put into a standard and in common sense it means all modes that go beyond VGA standard, most notable 800x600 resolution.
A lot of early VGA cards (like the Paradise PVGA1A) are capable of 800x600 at 16 colors at e.g. 56 Hz interlaced with just 256K of RAM. So in that sense these cards are Super VGA.
Just look at the support of graphics cards in FractInt and you will see that most of the early cards are actually Super VGA because they offer one or more modes that go beyond IBMs VGA from 1987.
So since Super VGA includes VGA the minimum requirement is the same as VGA with 256K.

However all of these modes were proprietary implemented and in 1989 the VESA consortium standardized an API to use Super VGA modes in a generic way. One of the first modes was 640x480 at 256 colors requiring >256K RAM, which from a hardware constraint resulted in 512K. Now for early Super VGA games like Sim City 2000 the term Super VGA refers to the fact that the game uses 640x480 at 256 colors and thus requires a 512K+ card with VESA support.
So if you talk about Super VGA modes following the VESA API then the card must have at least 512K.

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Reply 10 of 21, by Anonymous Coward

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Can the PS/2 Display Adapter show 800x600?

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Reply 11 of 21, by Jo22

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elianda wrote on 2020-03-09, 09:50:

However all of these modes were proprietary implemented and in 1989 the VESA consortium standardized an API to use Super VGA modes in a generic way.

With one special exception (speaking under correction 😅 ). The 800x600 mode in 16c (the SVGA mode, per se) uses the default VGA palette,
so the memory layout is the same as that of 640x480, if memory serves me well.
Provided that the correct mode number is known, 800x600 mode can be universally used often - without the need for VBE.
800x600 mode also was special in that i had two VBE numbers, 6Ah (106 dec) and 102h (58 dec).
http://www.phatcode.net/res/221/files/vbe20.pdf

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Reply 12 of 21, by derSammler

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elianda wrote on 2020-03-09, 09:50:

The OPs question is a bit misleading.

What's misleading about the question: "Does anyone know what is the minimum video RAM required for 640x480 256 colors?"

?

It's quite spot-on to me.

http://retro-net.de/blog.html

Reply 13 of 21, by BinaryDemon

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Maybe it’s the title vs actual question being asked.

Check out DOSBox Distro:

https://sites.google.com/site/dosboxdistro/ [*]

a lightweight Linux distro (tinycore) which boots off a usb flash drive and goes straight to DOSBox.

Make your dos retrogaming experience portable!

Reply 14 of 21, by derSammler

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Since 640x480 256 colors is SVGA, the title is a perfect short version of his question. It's only not if the title would be the actual question with no further details given.

http://retro-net.de/blog.html

Reply 15 of 21, by Grzyb

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Anonymous Coward wrote on 2020-03-09, 10:42:

Can the PS/2 Display Adapter show 800x600?

Yes, plain VGA can be tweaked into 800x600, but at some abnormally low refresh rate.

Reply 16 of 21, by Anonymous Coward

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Let me guess...53Hz interlaced.

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Reply 17 of 21, by ntalaec

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As derSammler said, I used a short question for the title.

I had and OAK card back in the day (OTI-067 I think) and I don't remember the amount of RAM it had, but I remember it could do 640x480x256 in Windows 3.1.
Microsoft's article says that it's possible 640x480x256 with 256 KB but according the formula to determine the amount of RAM at the end of the page it is not. So I came to Vogons to confirm if it was possible in Windows 3.x or it was an error.

Reply 18 of 21, by Grzyb

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Anonymous Coward wrote on 2020-03-09, 15:31:

Let me guess...53Hz interlaced.

According to my monitor, 29.3 kHz / 45 Hz.
Definitely non-interlaced, and I even doubt that plain VGA can do interlace.

Reply 19 of 21, by BinaryDemon

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ntalaec wrote on 2020-03-09, 15:55:

As derSammler said, I used a short question for the title.

I had and OAK card back in the day (OTI-067 I think) and I don't remember the amount of RAM it had, but I remember it could do 640x480x256 in Windows 3.1.
Microsoft's article says that it's possible 640x480x256 with 256 KB but according the formula to determine the amount of RAM at the end of the page it is not. So I came to Vogons to confirm if it was possible in Windows 3.x or it was an error.

Are you positive it was 640x480x256 and not 640x400x256? I think you can squeeze 640x400 into 256kb.

Check out DOSBox Distro:

https://sites.google.com/site/dosboxdistro/ [*]

a lightweight Linux distro (tinycore) which boots off a usb flash drive and goes straight to DOSBox.

Make your dos retrogaming experience portable!