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
