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Thread: 10MHz 8088 fast enough for VGA Mode 13h?

  1. #1

    Default 10MHz 8088 fast enough for VGA Mode 13h?

    As the title says, is a Turbo 8088 (or NEC V20) fast enough to make the Mode 13h chunky 320x200 usable, or is VGA just not a good match? I am specifically looking to play around with programming games, etc. as a “new” platform moving from Commodore 64. I know VGA doesn’t have any of the hardware, but the 256 color simple chunky graphics mode is very appealing. Just don’t know if I’m setting myself up for dissapointment or not...

  2. #2
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    It totally depends on what you are doing with the graphics. Something like Doom would obviously not work, but there were some VGA programs that ran acceptably on an 8088 based systems. Looking at some of the games that were out there might give you a better idea, although keep in mind that most programs of the time were not well optimized as vendors just assumed people would buy faster computers.

  3. #3

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    I remember Prince of Persia running pretty well on a turbo 8088 in VGA.

    It could only run smoothly at 4.77 in CGA mode. 8-bit pixels are a bit heavy for a stock XT without some very careful coding, and in a lot of cases it's still going to be a bit heavy anyway. Depends what needs to happen on the screen.
    Last edited by Mike Chambers; July 14th, 2020 at 05:26 PM.

  4. #4

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    Quote Originally Posted by Mike Chambers View Post
    I remember Prince of Persia running pretty well on a turbo 8088 in VGA.

    It could only run smoothly at 4.77 in CGA mode. 8-bit pixels are a bit heavy for a stock XT without some very careful coding, and in a lot of cases it's still going to be a bit heavy anyway. Depends what needs to happen on the screen.
    It wasn't exactly smooth in CGA mode, either. If you compare it to the performance of the original Apple II version, it's pretty obvious that they could've done better.

    Not that I've looked at the code, but it wasn't unknown for certain companies to use 6502-to-8088 ASM translation tools when porting games to the PC, and the results weren't exactly optimized.
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    Quote Originally Posted by mrarkus View Post
    As the title says, is a Turbo 8088 (or NEC V20) fast enough to make the Mode 13h chunky 320x200 usable, or is VGA just not a good match?
    It's a simple question of bandwidth: It depends on how many pixels you're going to be updating at a time. Your memory bandwidth to a VGA card on an 8MHz NEC V20 is going to be somewhere between 240KB/s and 360KB/s. If we assume the best, that would equate to about (360/64=) 5.6 frames per second if you're updating the entire screen every game tick. However, game rendering isn't free, so you should roughly divide that in half, so it would be reasonable to expect a framerate of about 3fps if you're updating the entire screen every frame.

    So the trick is not to update the entire screen every frame There are some games that only update portions of a frame, such as graphical adventures where you move a small character around a static screen, and those would be just fine. Or, if you had to update a large portion, maybe settle for half the screen, like a driving viewport on top and the dash/steering wheel on the bottom.

    One of the most well-optimized games I know of to showcase systems is Indianapolis 500. Download that, and run it on your system and watch the (impressive) demo that plays when you hit a key at the title screen. Note how it looks visually. Then, rerun it with "indy /c" to force CGA mode, and then watch the demo, and you'll notice it's faster because it has to update 1/4th of the memory that it would have to update with mode 13h.

    Maybe if you mentioned what kind of game you were thinking of, we could offer more targeted advice and techniques.
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  6. #6

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    Battlestorm by Titus runs well on 8088-8 / 8088-10 with smooth scroll on VGA (320x200)

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    I am using Elite Plus on my Turbo XT with V20 8MHz system. It works in mode 13h, but is quite laggy. In 0dh mode (320x200 16 colors using 4 bit planes) it is much more snappy.

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