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Why CGA?

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First post, by ChaosFish

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Again, sorry for being a n00b, but I just don't get it.

What's with that evolution from CGA, then EGA, then VGA, etc.?

Why didn't we just start with SVGA? I mean, why use palettes? Are old computers really can't handle telling the monitor to use more than 4 colors at once while the monitor obviously *can* do it?

Explanations please 😀

Reply 1 of 31, by MiniMax

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I think it is a matter of memory requirements (and price). Do the math:

4 colours = 2 bits. Memory = 2 * x-res * y-res.
16 colours = 4 bits. Memory = 4 * x-res * y-res
256 colours = 8 bits. Memory = 8 * x-res * y-res.

My first computer (non-PC) came with a whopping 2,048 bytes of memory, some of which was shared with the graphics controller (an MC-6847) allowing me the luxury of these graphics modes:

64x64 in 4 colour (or rather shades of grey, since the little portable TV I used for a monitor was black/white) = 1,024 bytes
64x96 in 4 colour = 1,536 bytes
128x96 (monochrome) = 1,536 bytes
128x92 (2 colour) = 1,472 bytes

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Reply 2 of 31, by ribbon13

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I remember when a 8088 running at 4.77mhz with 10mb Seagate Winchester drive, controller, and CGA card cost $4500.

Now you can get a 2ghz sempron with 512mb ram, 120gb hdd, and entry level gpu for under $600

Besides
Why didn't we just start out at QUXGA-Wide???
http://en.wikipedia.org/wiki/Computer_display_standard

Reply 3 of 31, by fish

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Has nothing to do with being a n00b. (I hate this "coolwriting" anyway)

Back in those days when the IBM PC and the IBM PCjr came out, most monitors had a fixed Hz rate and monochrome displays still had a good market share. There were even monochrome graphics adaptors. Back then writing software was chopping wood with an axe compared to todays application building tools, which are like burning the whole forest down.

You had to deal with very limited hardware. Most PCJr came out with as much as 64 KB of memory, the better models shipped with 128 KB. A Harddrive was not standard to have.

For a monochrome display it was quite a demand to display more than 16 shades of grey. In fact, you didn't need more because you could simulate more colors with dithering and most application software didn't want more.

The PC was a working machine, not a gaming computer (the PCjr is another story)

Now more colors need more memory to store and more processor load to handle.

A 320*200*4 screen needs 16 k of memory. It needs 64.000 times the operation "make color X, pixel counter +1" which is all done through the humble CPU which should also run the application code, the OS, the BIOS calls, drivers... you get it.

Now with 16 colors, you already need a half byte (nibble, 4 bit) to store just one pixel in display memory (and on disk). A whole 320*200 screen would take up 32k memory. In 256 color palette mode, the very same screen takes 64 k, 1 byte per pixel. For 256 colors, you needed a decent monitor. Now you could say why not make a 320*200*32bit capability which would only take up 64k*4=256 KB.

Well, the typical floppy drive of the time could read 360 KB diskettes. The PC was no gaming machine, higher resolution was considered more important than fancy colors.

Just keep asking questions, there's a good deal of graphics history that I never really got either. Just think about the PCjr/tandy mode. Just think about VESA history.
What's MCGA, anyway?

Reply 5 of 31, by Sol_HSA

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MCGA was Multi-Color Graphics Array, basically an EGA with the addition of mode13h. (320x200x256c).

I've never seen one, but I assume VGA came out right after that, and thus it never got too popular.

http://iki.fi/sol - my schtuphh

Reply 6 of 31, by zorach

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Sol_HSA wrote:

I've never seen one, but I assume VGA came out right after that, and thus it never got too popular.

They came out very close to or at the same time. The low-end PS/2 models (such as the model 20) had MCGA.

Reply 8 of 31, by mirekluza

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robertmo wrote:

Why were they called ps/2? Does it have anything in common with todays ps/2 mouse and keyboards? And there are SIMM memory modules also called PS/2.

PS/2 mouse and keyboard - they are called like that because of connectors (which I guess were introduced by PS/2 computers). I remember having a computer without them. In case of keyboard just the size of connector differed (it was bigger - there are reductions), in case of mouse there was a completely different connection (I had a mouse for serial port).

Mirek

Reply 9 of 31, by robertmo

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http://pages.prodigy.net/michaln/history/os210/ps2.html

"While PS/2 computers did not take over and the line was ultimately discontinued by IBM, the introduction of PS/2 is without any doubt an important milestone in PC history. A great number of innovations that first appeared in the PS/2 line was adopted by the industry (apart from VGA and 1.44MB floppies there were for instance PS/2 keyboards and mice or PS/2 72 pin memory modules). PS/2 machines were built to last and some of them are still happily running, years and years after they were built, a tribute to IBM's conservative, built-to-last engineering so unpopular these days."

😀

Reply 10 of 31, by [vEX]

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Oh, our first PC was an IBM PS/1, which was a normal PC running DOS/Windows.
It was a 486SX 25MHz, 2MB RAM, 80MB HDD and it came with a 14" SVGA monitor!

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Reply 11 of 31, by HunterZ

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From what little I know, the PS/2 was an attempt by IBM to market a closed-architecture PC to regain a foothold on the market, which had been flooded by clones. It had a different bus architecture from other PCs at the time (MCA - micro-channel architecture - instead of the 8- and 16-bit ISA and soon after 32-bit VLB/PCI used by normal PCs). It didn't do well enough to take over as the standard for PCs, and the only traces left of them in modern computers are the PS/2 mouse and keyboard ports that are now standard (which replaced the serial port as a mouse interface and giant "AT connector" for keyboards). USB is better IMO because of its hot-swapping/plugging ability (e.g. you can't plug in a PS/2 mouse after booting the computer without one and have it work, unless you reboot again).

Reply 12 of 31, by mirekluza

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HunterZ wrote:

USB is better IMO because of its hot-swapping/plugging ability (e.g. you can't plug in a PS/2 mouse after booting the computer without one and have it work, unless you reboot again).

Yes, but personally I never needed this (it is usefull for flash discs/cameras/MP 3 players/etc but hardly ever for keyboard/mouse).
I like PS/2 ports better. I got used to them and they have no problems with supporting plain DOS. The only think I hate is occasionally confusing mouse/keyboard connectors. But since I connect mouse/keyboard just once in a long time it is no problem.

Mirek

Reply 13 of 31, by eL_PuSHeR

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Agreed. USB mice doesn't work under plain ms-dos, don't they?
Besides, PS/2 ports work quite well. This issue remind me of another one: manufacturers have stopped using good ole' reliable LPT parallel port for the new usb for printers. I find it rather stupid. My Laserjet 1200 uses the standard parallel port and never had any problems. It even prints handy dandy under plain ms-dos.

Reply 14 of 31, by mirekluza

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eL_PuSHeR wrote:

Agreed. USB mice doesn't work under plain ms-dos, don't they?

I think that some of them do, but a speciall driver is required (which may or may not be available).
PS/2 is certainty. But of course I know that sooner or later PS/2 will disappear anyway...

Mirek

Reply 15 of 31, by HunterZ

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Parallel port printers under Windows piss me off because they never use simple drivers. Instead, they always have some bloated utility that runs whenever you print something, which causes all sorts of problems. I haven't tried USB printers, but I hope they're better in that regard.

el_pusher: Also, I think you're right about USB mice not working under DOS, but if you're running pure DOS then the system should have a PS/2 or serial port for mice. My point is that there really isn't any need for them on modern PCs that run Windows or Linux or whatever.

Reply 16 of 31, by DosFreak

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eL_PuSHeR wrote:

Agreed. USB mice doesn't work under plain ms-dos, don't they?

Sure, they do and for quite some time. Along with CDROM, USB Flash, ZIP, and Hard Drives.

http://www.stefan2000.com/darkehorse/PC/DOS/Drivers/USB/

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Reply 17 of 31, by DosFreak

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HunterZ wrote:

USB is better IMO because of its hot-swapping/plugging ability (e.g. you can't plug in a PS/2 mouse after booting the computer without one and have it work, unless you reboot again).

Technically, your not supposed to plug/unplug PS/2 devices while your PC is powered on....but we all do it anyway. 😀

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