If you think there is a processor chip built into the LCD, then, yes, you are.
On Sat, 21 Feb 2026 at 10:46, B9 <[email protected]> wrote: > (Note: I may ALSO be confused about how the Hitachi LCD works!) > > > On February 21, 2026 10:35:00 AM PST, B9 <[email protected]> wrote: > >> Sorry, I'm using the wrong words. I may also be confused about Virtual T. >> Most likely both! :-) >> >> By "emulate", I was thinking of a chip-level emulation. When you said the >> "model" is not 100% accurate, I thought you were talking about a black-box, >> function-level emulation. >> >> Does Virtual-T emulate the processor built in to the LCD? >> >> --b9 >> >> P.S. Can one manipulate the LCD using OUT on Virtual T? >> https://github.com/LivingM100SIG/Living_M100SIG/blob/main/M100SIG/Lib-10-TANDY200/SCROLL.200 >> >> >> >> >> >> On February 20, 2026 8:05:55 PM PST, Kenneth Pettit <[email protected]> >> wrote: >> >>> Umm, >>> >>> I'm not sure what you mean. VirtualT *does* emulate the LCD controller >>> chips. Just maybe the timing of BUSY is not modeled accurately. >>> >>> Ken >>> >>> On 2/20/26 1:53 PM, B 9 wrote: >>> >>> Are there hooks in Virtual T so that someday it might be able to emulate >>> the LCD controller chips? I noticed that the MAME ROMs for the Tandy 200 >>> included the Hitachi ROM, if that was what was holding up development in >>> Virtual T. >>> >>> Besides timing accuracy, there are some esoteric features missing which >>> Virtual T won't be able to do until it gets full LCD emulation. (If I >>> recall correctly, smooth scroll and text mode didn't work, I'm not sure >>> offhand what else.) >>> >>> —b9 >>> >>> >>> On Fri, Feb 20, 2026 at 11:26 AM Kenneth Pettit <[email protected]> >>> wrote: >>> >>>> Yes, there is no doubt that VirtualT runs too fast wriring to the >>>> screen. Even with the 8085 running at 2.4 MHz, it is still fasterr than >>>> the LCD controller chips. The ROM polls the LCD controller for "BUSY" >>>> status after writing new data an will only continue once the controller is >>>> ready. I tried to model this in the emulation, but it moster certainly is >>>> not 100% accurate. >>>> >>>> Ken >>>> >>>> On 2/19/26 10:28 PM, B 9 wrote: >>>> >>>> This may be just more of the same problem, but it appears Virtual T >>>> runs too fast when printing to the screen as well. >>>> >>>> [image: image.png] >>>> >>>> I noticed this because the BASIC loader >>>> <https://github.com/hackerb9/co2do/> I made for .co files is >>>> superduper slow and the reason is (partly) due to constantly printing the >>>> status. If anyone knows a fast way to display on the screen, please do let >>>> me know. >>>> >>>> To test, I printed strings of different lengths and measured the >>>> elapsed time. On my actual Tandy 200, it was a linear relationship for >>>> strings from 0 to 39 chars: n×16÷9+5. Virtual T seems to be going about >>>> twice as fast with a speed of about n+3 seconds for printing an n-character >>>> string 1000 times. >>>> >>>> —b9 >>>> >>>> >>>> >>>> On Mon, Feb 9, 2026 at 3:39 PM B 9 <[email protected]> wrote: >>>> >>>>> Virtual-T seems to be running too fast for me compared to real >>>>> hardware (Tandy 200). I could be doing things wrong, so it’d be helpful if >>>>> other people checked this out as well. >>>>> >>>>> Experimentally, my Tandy 200 takes 10 seconds to count to 3535. >>>>> >>>>> FOR T=1 TO 3535: NEXT >>>>> >>>>> When I do the same thing on Virtual-T’s emulated T200 it takes only 6 >>>>> seconds. >>>>> Machine Time to count to 3535 >>>>> Genuine T200 10s >>>>> Virtual-T 1.7 T200 6s >>>>> Virtual-T 1.7 M100 5s >>>>> >>>>> Is the same thing true for other folks with real hardware? What about >>>>> the Model 100 and Tandy 102 (or other more esoteric of the Kyotronic kin)? >>>>> >>>>> Second thing: REX# seems to slow my machine down significantly when I >>>>> do not have an Option ROM activated. It is completely repeatable. Is this >>>>> a >>>>> known issue? I tried using the emulated REX in Virtual T, but I must have >>>>> an old version as it only had REX and REX2 listed, not REX#, and those >>>>> didn’t cause any slowdown. >>>>> Machine and REX# setup Time to count to 3535 >>>>> Genuine T200 with REX# De-installed 10s >>>>> Genuine T200 with REX# Installed, but no Option ROMs activated 16s >>>>> Genuine T200 with REX# Installed and any Option ROM activated 11s >>>>> >>>>> Finally, here’s a program that makes it easy to run timing tests >>>>> repeatedly. >>>>> >>>>> 0 REM Speed Check4 COUNT=3535 ' T200 takes 10s to 35355 PRINT"Counting up >>>>> to";COUNT6 PRINTTIME$10 T1$=TIME$20 FOR T=1 TO COUNT: NEXT30 T2$=TIME$: >>>>> PRINTT2$40 H1$=MID$(T1$,1,2)50 M1$=MID$(T1$,4,2)60 S1$=MID$(T1$,7,2)70 >>>>> H2$=MID$(T2$,1,2)80 M2$=MID$(T2$,4,2)90 S2$=MID$(T2$,7,2)110 >>>>> H2=VAL(H2$):H1=VAL(H1$)120 M2=VAL(M2$):M1=VAL(M1$)130 >>>>> S2=VAL(S2$):S1=VAL(S1$)150 IFS2<S1THENS2=S2+60:M2=M2-1:GOTO 150160 >>>>> IFM2<M1THENM2=M2+60:H2=H2-1:GOTO 160170 IF H2<H1 THEN H2=H2+12: GOTO >>>>> 120180 H=H2-H1: M=M2-M1: S=S2-S1190 PRINT"Ran";COUNT;"loops in";200 >>>>> PRINTUSING"##h##m##s";H;M;S >>>>> >>>>> Please let me know what you find. Thanks all! >>>>> >>>>> —b9 >>>>> >>>> >>>> >>>
