PCEm. Another PC emulator.

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Re: PCEm. Another PC emulator.

Postby Xenphor » 2018-7-27 @ 06:14

I'm having issues with PCem and vsync. I'm trying to get it as smooth as it would be on the original hardware with no stutters at all, but it doesn't seem possible. This is most noticeable in old 2d games that have scrolling in them like Sonic 3D Blast. As I move sonic across the screen, there will be tons of hitching and hiccuping as the screen scrolls, kind of like what happens on emulators of consoles/arcades which run at a different refresh rate than your monitor. Using regular OpenGL seemed to help mitigate this somewhat, but it is still there; OpenGL 3 on the other hand made it a lot worse, as did Direct3D and software.

Games that use the voodoo2 for 3d Acceleration like quake 2 actually seem to run fairly smoothly. If I press either the left or right arrow keys to scroll the screen uniformly in one direction, I may only notice the occasional stutter (that is of course assuming I'm in an area that can maintain 60fps, like by staring at the ground in the beginning). However playing a game like this highlights another problem with the vsync in PCem: massive input lag. It seems to have much more input lag than your typical console or arcade emulator but I have no idea if this is even fixable.

So can the stuttering at least be fixed or do I need a gsync monitor?

I'm running the pentium 233 MMX machine on an 8700k with a 1050 ti card.
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Re: PCEm. Another PC emulator.

Postby hail-to-the-ryzen » 2019-1-21 @ 01:07

With the interpreter path for cpu emulation and OPL2 music, the video in Doom will not run at a sufficiently constant rate. Disabling the threading in the video blitter solves a lot of the issue. It also generally helps to have any vsync active. Tested in various DOS ports of Doom in the stock maps where the fps ranges from 14 to 22.
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Re: PCEm. Another PC emulator.

Postby Jo22 » 2019-4-02 @ 05:26

Jo22 wrote:Regarding that maximum conventional memory on page 45, again..
"I have found out that IBM PC 5150 continues BIOS memory test to 704 kilobytes with undocumented
SW2 DIP switch settings ON ON OFF ON OFF and DOS automatically uses all of that as conventional memory.
This is an alternative way to utilize 64 kilobytes of RAM at segment A0000.

Just tested that on a physcial XT clone w/ CGA. Managed to get 704KiB on that machine with an UMB card that made RAM available at A segment.
Utility used to make DOS aware of the extra 64KiB was 704K. After reboot, the BIOS saw 704KiB, too.

Edit: I sincerely apologize if that reply makes me seem stubborn,
but that bit of extra memory could perhaps be useful for running old CGA/MDA/HGC titles
together with earlier, period-correct DOS versions (2.11, 3.x) which are not aware of UMBs yet.

I know, 64KiB extra are not much, but these would cause about the least headache in comparison
and are about enough for allowing someone to use drivers for peripherals that weren't
so mandatory in the 80s but are now.

Especially mouse, keyboard and CD-ROM/network drivers.
Maybe Sound.com for AdLib, too.

In addition, some EMS LIMulators (Above Disc etc) could also use these 64KiB for
their pass-through window without hurting conventional memory too much.

Anyway, I'm not complaining or requesting a special support for that scenario.
It just would be good if changing the memory amount in PCem's config files manually beyond
640K would have an effect.
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In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Re: PCEm. Another PC emulator.

Postby doaks80 » 2019-4-02 @ 06:38

Its interesting that emulator deficiencies may never be resolved, as CPU have hit a limit for single threaded performance. I am really glad I built my collection of retro computers as everything just works so perfectly. And by the time my hardware dies ill be too old to play games anyway, if i dont die first. Life plan=complete.
k6-3+ 400 / s3 virge DX+voodoo1 / awe32(32mb)
via c3 866 / s3 savage4+voodoo2 sli / audigy1+awe64(8mb)
athlon xp 3200+ / voodoo5 5500 / diamond mx300
pentium4 3400 / geforce fx5950U / audigy2 ZS
core2duo E8500 / radeon HD5850 / x-fi titanium
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Re: PCEm. Another PC emulator.

Postby awgamer » 2019-4-02 @ 11:38

I imagine current 5+ghz cpus are enough to handle the worst dos game performers with dosbox, if not next gen ryzen supposed to top current in ipc, performance isn't being fully realized with no threading, recompiled code not written to be optimized, &/or adding qemu style/hardware cpu virtualization. virtualbox is fast enough to run 9x/2k/early xp, its issue being compatibility, and 9c+ not really needing emulation.
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Re: PCEm. Another PC emulator.

Postby Jo22 » 2019-4-03 @ 12:19

^Physical CPU cards with 80x86 would also be neat. I.e. in the style of Amiga Bridgeboard, the Z80 SoftCard, etc., but only with the core parts present.
By using an open source plug-in DLL, both emulators and virtual izers could use them optionally. Interface could be PCIe, Thunderbolt, USB etc.
I imagine that the NEC V20/V30/40, 80286-486SX -or a very good FPGA- would be most easily to interface with that,
since they have less pins than newer CPUs and weren't designed to be PC-only parts yet. Current CPUs are about to slowly loose the roots of x86.
If good ol' BIOS really is gone somewhen past 2020, there's little reason to keep Real-Mode or V86 in silicon, since essentially only x86-64 OSes are still able to boot natively, anyway.

Edit: Ironically, we have good Pentium level emulation, but no one managed to properly emulate the NEC V series yet,
even though it was THE #1 upgrade in early days of personal computing.
If we compare that to 8-Bit computing, then that's as if the 8080 was emulated, but not the Z80. ;)
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In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Re: PCEm. Another PC emulator.

Postby SarahWalker » 2019-5-19 @ 17:00

V15 is now available. Changes since V14 :
  • New machines added - Zenith Data SupersPort, Bull Micral 45, Tulip AT Compact, Amstrad PPC512/640, Packard Bell PB410A, ASUS P/I-P55TVP4, ASUS P/I-P55T2P4, Epox P55-VA, FIC VA-503+
  • New graphics cards added - Image Manager 1024, Sigma Designs Color 400, Trigem Korean VGA
  • Added emulation of AMD K6 family and IDT Winchip 2
  • New CPU recompiler. This provides several optimisations, and the new design allows for greater portability and more scope for optimisation in the future
  • Experimental ARM and ARM64 host support
  • Read-only cassette emulation for IBM PC and PCjr
  • Numerous bug fixes
As ever it's at http://pcem-emulator.co.uk
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Re: PCEm. Another PC emulator.

Postby realnc » 2019-5-23 @ 07:47

The best retro PC emulator just got even better. Been using this for a while now. I'm using it on Linux, and it seems there's a lot of performance to be gained by building with Clang and using PGO, run a few games in it, then rebuild with the gathered PGO data. This allowed my i5 to go from a Pentium 100Mhz to a Pentium 133MHz at full speed.

I tried the same with GCC + PGO, but the perf gains were rather minimal.
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