86Box / PCem performance differences \ VOGONS

86Box / PCem performance differences

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First post, by DeepestBlueDragon

Posted on 2026-09-30, 07:10

DeepestBlueDragon Offline

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Joined: 2026-09-30, 06:37

Hello folks,

I'm seeking some assistance with understanding differences in performance between 86Box and PCem.

Some basic information. My host PC is an i7-8086K, 64GB RAM, SSD boot and VM storage drives, 3060Ti, W10.

I have tried to set up both 86Box and PCem to emulate a PII-400, 256MB RAM, 16GB IDE HDD, S3 Virge DX 4MB, SB or compatible, no parallel/serial, Realtek NIC, running Windows 98 SE. OS installed the same way using the same media. No updates, just the base OS with built in drivers.

I've noticed that despite setting the two emulators to be as similar as possible, they are performing very differently. 86Box takes a LONG time to get into Windows (several minutes), whereas PCem boots in within a minute or two. However disc access in 86Box is significantly faster. I downloaded the DOSBENCH suite and ran it on both emulators. The results are attached in the screenshot and are also below.

It would seem that the way the emulators work seem to mean certain tests perform better on one than the other.

86Box performs faster in these tests:
- Landmark's CPU test (33% faster)
- Speedsys (15% faster)

PCem performs faster in these tests:
- Topbench (217% faster)
- Landmark Video test (231% faster)
- PC Player (26%)
- Chris's 3D Bench (24%)
- 3D Bench Superscape (23%)

On top of these, I booted up MHDD and did a read test. 86Box reported 914.8Mb/s, vs 62.2Mb/s in PCem. I suspect the difference here is because 86Box has an option for "Generic RAM Disk (Max Speed)" option in its HDD settings, whereas PCem doesn't.

So my questions here are:

1. Am I right in thinking the differences in performance are just down to how the two emulators work?
I love the customisations in 86Box, but PCem seems to perform better overall. Is there any way to
2. ...boost PCem's HDD speed?
3. ... increase 86Box's overall performance?

Thanks for the questions, and apologies if they're rather n00b-like; this kind of emulation is new to me. I'm more used to Proxmox and VirtualBox!

Reply 1 of 3, by DeepestBlueDragon

Posted on 2026-09-30, 07:13

DeepestBlueDragon Offline

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(Just noticed the MHDD line shows KB/S, should be Mb/s)

Reply 2 of 3, by jh80

Posted on 2026-09-30, 10:52

jh80 Offline

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Joined: 2025-06-16, 00:16

What versions of 86Box and PCem? And more importantly, which dynamic recompiler (or interpreter?) in 86Box? I think the new dynarec is similar to (or same as) PCem's, while the old dynarec is retained from before PCem updated.

Because (by default) both emulators have the dynamic recompiler enabled, what those CPU benchmarks are measuring is more about how efficient the dynarecs are in processing certain code. One emulator might be better in one context but worse in another depending on the code that is being processed by the dynarec. That's also why those CPU benchmarks also don't reflect necessarily how each emulator will handle a specific game. Essentially, each and every game will likely have slightly different performance.

Reply 3 of 3, by Battler

Posted on 2026-09-30, 12:25

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Joined: 2014-03-22, 21:27

Also, 86Box and PCem have entirely different Pentium II timings - 86Box's were written by Plant based on the K6 timings and tweaks using real Pentium II benchmarks as a reference.

PCem also defaults its video timings to 8-bit ISA, which may yield increased % at the expense of much slower video memory affected - setting them to the option named Default (yes, it's confusing!) should bring them on par.

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