slowdowns in XT and IBM AT 286 emulation

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Fenix77
Posts: 30
Joined: Fri 01 Sep, 2017 11:59 am

slowdowns in XT and IBM AT 286 emulation

Postby Fenix77 » Fri 01 Sep, 2017 1:23 pm

Hello, everbody.

I'm new in the forum. I'm not an English speaker.

PCEM is my favourite emulator because it is focused to emulate accurately the old hardware of '80 and '90. I used to have a Turbo XT in early '90, whit no hard disk. a 360kb floppy, an Hercules monochrome graphics card and a Phospor amber monitor.

I find specialy interesting, the posibility to use EMS memory (like Laser XT) and a Hard drive in these machines, because back in the day it was too expensive.
(I now i can see how it worked with Windows 2.0 and its apps)

It is a very interestig proyect for gaming and historic purpose.

I use other emulated hardware for Windows 3.1 and 95 too. But i found more interest the machines od late '80.

Now, the bugs.


First i discovered that the Vtech Laser XT 3 has an 8086 CPU running at 10 Mhz, according the Manual http://www.minuszerodegrees.net/manuals/VTech/VTech%20Laser%20XT3%20-%20Operations%20Manual.pdf

Also I' want to report a bug in the emulation on XT machines an IBM AT 286. The promblem is a slowdown that happen in certain games with these machines.
Some of them can render the game unplayable.

And it can Lock up the system if VGA card is used.

The games and MAchines I Tested:

Whit Vtech Laser Turbo XT and XT 3, Tandy 1000 SL/2 (with tandy 3-voice and DAC) and Amstrad 1640 with EGA graphics, And IBM AT 286 with VGA.

* Prince of Persia 1.0 and 1.3: The slowdown is more noticeable when the guard or the animation of fire is present. And if VGA is used the system may Lock-up

And whit Laser XT and XT 3 with Hercules And CGA.

* Bubble Bobble: It has a lot of it. (specialy when more than 3 enemies appear)
* Tetris (Spectrum Holobite, 1987): The games run flawlessly, no problem here.
* Tom & Jerry Cat-Astrophe: The slowdown is less noticieble.

Another Problem is that some CGA emulators for the Hercules Card, does not work. (for example the emulator MONO.COM. Back in the day i used it for Bubble Bobble.)

i Attached the file here (Mono.com). It works even in Dosbox with Indiana Jones and Last Crusade (from Us Gold 1989).


I'm grateful to the Devs. and the Contributors, who brought back to life these old and little known hardware.
Attachments
MONO.zip
(819 Bytes) Downloaded 10 times
Fenix77
Posts: 30
Joined: Fri 01 Sep, 2017 11:59 am

Re: slowdowns in XT and IBM AT 286 emulation

Postby Fenix77 » Fri 01 Sep, 2017 7:31 pm

I just forgot to mention, my host machine is a laptop with i5 4210u with 6 GB ram and Nvidia 820M and Windows 8.1.

I just tested Prince of Persia 1.0 with the mainline version PCem V12 with C2Duo machine with Windows XP.
And configured PCem with Vtech Laser XT with Hercules Card.

The slowdown is much less noticeable, in this machine. But i played this game in both, 86box and PCem v12 and both had the slowdown problem in my laptop.

interestringly Pince of Persia worked without any issue in Pcem V11
SarahWalker
Site Admin
Posts: 1317
Joined: Thu 24 Apr, 2014 4:18 pm

Re: slowdowns in XT and IBM AT 286 emulation

Postby SarahWalker » Sat 02 Sep, 2017 1:42 pm

Could you provide the pcem.cfg you're using with the IBM AT?

The timings for 286 and 386 CPUs were reworked between v11 and v12 to be more accurate. So the AT will be slower in v12, but closer to the real machine than v11 was.

The slowdown in Prince of Persia may be genuine. I've just tried it on a real 8088/10, where it is essentially in slow motion. I suspect a 286/6 may not be quite fast enough either. I haven't seen it lock up though. Does it occur at any specific point or is it at random?
JosepMa
Posts: 70
Joined: Tue 20 Jun, 2017 6:25 pm

Re: slowdowns in XT and IBM AT 286 emulation

Postby JosepMa » Sat 02 Sep, 2017 3:22 pm

Just if it serves as any guideline:
I have a friend that had Prince of persia on a 286 at 12MHz (12 IIRC) with a CGA display (Don't know the make/model. It was a PC integrated into a keyboard, including a 10MB HDD and a FDD ).
The game was quite playable, but I don't remember much more than that.
To have it in perspective: doing a "dir" on C: you could see how it printed line by line. :P
Fenix77
Posts: 30
Joined: Fri 01 Sep, 2017 11:59 am

Re: slowdowns in XT and IBM AT 286 emulation

Postby Fenix77 » Sat 02 Sep, 2017 10:02 pm

Hello.

Thanks for the reply.

here is the pcem.cfg using IBM AT 286.

gameblaster = 0
gus = 0
ssi2001 = 0
voodoo = 0
model = 20
cpu_manufacturer = 0
cpu = 1
cpu_use_dynarec = 0
cpu_waitstates = 0
gfxcard = 11
video_speed = 0
sndcard = 0
cpu_speed = 0
has_fpu = 0
disc_a =
disc_b =
mem_size = 2048
cdrom_drive = 0
cdrom_enabled = 1
cdrom_channel = 1
vid_resize = 1
vid_api = 1
video_fullscreen_scale = 0
video_fullscreen_first = 0
hdc_sectors = 63
hdc_heads = 16
hdc_cylinders = 60
hdd_sectors = 0
hdd_heads = 0
hdd_cylinders = 0
hdd_fn =
hde_sectors = 0
hde_heads = 0
hde_cylinders = 0
hde_fn =
hdf_sectors = 0
hdf_heads = 0
hdf_cylinders = 0
hdf_fn =
drive_a_type = 5
drive_b_type = 0
window_w = 0
window_h = 0
window_x = 0
window_y = 0
window_remember = 0
joystick_type = 0
mouse_type = 0
enable_sync = 1
midi = 0

[Joysticks]
joystick_0_nr = 0
joystick_1_nr = 0

[Paradise Bahamas 64 (S3 Vision864)]
memory = 2

[Sound Blaster AWE32]
onboard_ram = 2048

I recently played Prince of Persia 1.0 with IBM 286 and VGA, and Tandy 1000 SL/2 too, with PCEM v12,the slowdown is very little and the game is completely playable.
In fact the i belive this is the normal behavior, i played the game with IBMulator (emulates PS/1 2011) and it has the same delays.

Sorry, I suspect the issue exist only in the SVN version of 86box, maybe it was introduced in some commit.

I sometimes use 86box to test the new emulated hardware and the improvements in the emulator interface, hence i didn't remember on which of them the issue occurred.

By the way. If i may ask. The new features introduced in 86box, is for testing purpose and will be merged in Pcem?
or 86box is meant to be a fork, based on mainline PCem with more features?
SarahWalker
Site Admin
Posts: 1317
Joined: Thu 24 Apr, 2014 4:18 pm

Re: slowdowns in XT and IBM AT 286 emulation

Postby SarahWalker » Sun 03 Sep, 2017 8:14 pm

86box is opening a massive can of worms, all I will say here is that I have nothing to do with it.
Battler
Posts: 793
Joined: Sun 06 Jul, 2014 7:05 pm

Re: slowdowns in XT and IBM AT 286 emulation

Postby Battler » Mon 04 Sep, 2017 5:59 pm

- Fenix77: If the games run from a floppy, it could be the floppy emulation that slows it down. 86Box has more accurate floppy timings than PCem. But if it is the floppy slowing down the game, then the same should happen on real hardware.
Fenix77
Posts: 30
Joined: Fri 01 Sep, 2017 11:59 am

Re: slowdowns in XT and IBM AT 286 emulation

Postby Fenix77 » Tue 05 Sep, 2017 2:44 am

Hello.

Sorry for my english. I'm not an english speaker.

The problems happen with the games installed in the hard disk too. For Prince of Persia I created a subfolder in C:\ and copied the files there.
I found a web page witch has the original files. I could recreate the game in two 5.25 360kb or one 3.5 720kb img file with Winimage.
The web page has both versions (1.0 and 1.3).
I don't know if the game can be upload here because i don't know if the company (broderbund) still hold the copyright.

I have other games for 8088/8086 systems but not in the original disk or image file format.

The slowdown happends when scrolling text in some dos apps too. For example i opened the menu help of dr-dos 6 disk optimizer and was too slow.
It seem to be a keyboard slowdown. I use the keyboard for Prince of Persia and Disk optimizer. It does not support mouse unlike the Ms-dos 6's defrag.

Strangely some games like Spectrum Holobyte Tetris from 1987. runs with no issues, while other games like Bubble Bobble exhibit the same slowdown.

The rest of the aplications runs flawlessly.

I tested with several XT machines with pc-dos 3.20 and dr-dos 6. I Installed Windows 2.03 on Laser Turbo XT with EMS memory and serial mouse emulation.
The windows apps, such as Write and Paint runs ok. The apps can run even faster if a 256kb disk cache is installed in expanded memory with Pc-kwick.
I even defragmented an emulated 20 Mb MFM hard disk successfully with dr-dos disk optimizer with no issues, except for the keyboard scrolling or when i open the menu
with the keyboard shortcuts.
Battler
Posts: 793
Joined: Sun 06 Jul, 2014 7:05 pm

Re: slowdowns in XT and IBM AT 286 emulation

Postby Battler » Tue 05 Sep, 2017 1:06 pm

- Fenix77: As I told you on the 86Box GitHub, I'm going to compile you a PCem executable based on the latest binary code so you can try there. You jumped a bit to conclusion about it being an 86Box problem because it doesn't appear in PCem v12 stable, because for a fair comparison, you should compare against PCem dev rather than stable.

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