Program by chjmartin2 to run on GWBASIC TANDY simulates 85 colors viewer.
A free, cross-platform emulator for GW-BASIC, PCjr & Tandy BASIC
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Hi there!!! "Mr. chjmartin2" from VCF forum made a program for GWBASIC on TANDY (that works fairly on DOSBOX) can view images of 24-bits splitting screen pages that simulates 85 colors in a simple, but a very clever program, which I will like to see if PC-BASIC can handle. I tried but, it didn't work. I got a blank screen, thou it froze. Here's the article site:http://nerdlypleasures.blogspot.com/2016/01/milestones-in-ibm-pc-compatible.html in the topic: 2012 - Tandy 85-Color Picture Viewer. In the mentioned forum can download the program code to run giving also a copy of GWBASIC for running on an actual TANDY or emulated with DOSBOX.
I can give you the code, but I don't know if it's proper to do so; it's better if you unzip, unprotect, and run the "tview.bas" file and to study its behaviour for using it on PC-BASIC emulating TANDY. If no infringements is been done on attaching the code, let me know to reply it and some images too. I guess that it's not working because of the WAIT statements, but I'll let that to you. I just wanted to know how bad the flikering is in PC-BASIC instead of DOSBOX.
Ronald.
It's not working because of the
WAITstatements, and I have no idea what these are supposed to do in this case. Only a very small number of machine ports (whichWAITaccesses) are emulated in PC-BASIC, and it's not likely that many more will be.If I understand the discussion in the forum correctly, the demo uses some trick involving a quick flickering or maybe switching between video pages on a CRT monitor to generate more colour shades than usual, using the fact that the phosphors of a CRT keeps glowing for a bit after the screen changes colour. Not to put too fine a point on it, this is never going to work on PC-BASIC. PC-BASIC is not the right platform to try out these kinds of video/hardware tweaks, it's meant for running BASIC programs.
DOSBox can be surprisingly good at video tweaks, because it's maintained by people from the demo scene who focus on simulating such features especially if they were used in old games or demos, but really you need the original hardware for these kinds of tricks.
Yes, the WAIT statement is like a port and WAIT &H3DA, 8 is to stop flickering. That I understand, but still the SCREEN 5,,1,1,0 statement for page 1 and SCREEN 5,,2,2,0 for page 2 looks like it's not working. I could displayed the images, but I don't know why the pages function is not working proerly. Can you veryfy if SCREEN 5,,2,2,0 is a diffrent page than page1?
Thanks,
Ronald.
Edited: Okay, SCREEN 5,,0,0,0 Should be the first page. and is the only page that holds a BLOAD image, SCREEN 5,,1,1,0 is the second page that displays an image.done by commands but doesn't hold an image by BLOAD. SCREEN 5,,2,2,0 is a third page, and as same as page 2, definitely is not holding any image after a BLOAD. This should be considered a bug.
Ronald.
Last edit: Ronald Herrera 2017-08-07
Chris Here - found this post 3 years later. The WAIT statement is for the vertical retrace to occur. It allows you to wait until the beam is not drawing active screen to update the page data from one image to the other. The images themselves are interlaced in light and dark bands so that both images have an overall similar brightness and that is why it reduces the apparent flicker even on non-CRT although it works absolutely the best on an old RGB CGA TTL Monitor.