No worries,
Yes, VirtualT emulates the hardware of the controllers on the LCD
panels, including the T200 controller. It emulates the same 8K ram,
"start of LCD" pointer within that 8K RAM as well as all I/O commands.
This is what allows the ROM to operate "as is" ... VirtualT is a
hardware emulator.
The first step to making VirutalT "speed compliant" would necessarily be
to fix the CPU cycle timing in Linux (there should be no reason for it
to be faster than the Windows implementation, yet it is). Then after
that focus on any LCD / peripheral timing differences.
Ken
On 2/21/26 10:35 AM, B9 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.200or.
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.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 Check 4 COUNT=3535 ' T200 takes 10s to 3535
5 PRINT"Counting up to";COUNT 6 PRINTTIME$ 10 T1$=TIME$
20 FOR T=1 TO COUNT: NEXT 30 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 150 160
IFM2<M1THENM2=M2+60:H2=H2-1:GOTO 160 170 IF H2<H1 THEN
H2=H2+12: GOTO 120 180 H=H2-H1: M=M2-M1: S=S2-S1 190
PRINT"Ran";COUNT;"loops in"; 200
PRINTUSING"##h##m##s";H;M;S |
Please let me know what you find. Thanks all!
—b9
