Re: 64-bit dynamic_x86 (patch)

Posted on 2019-12-03, 03:38

by

by jmarsh

in DOSBox Development

in DOSBox Development

Thanks. It seems the newer a CPU is, the worse performance it has for the POPF instruction (thanks a lot, speculative execution bug mitigations) so avoiding it as much as possible is a good idea.

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Re: DOSBox Feature Request Thread

Posted on 2019-12-03, 01:20

by

by jmarsh

in DOSBox General

in DOSBox General

You couldn't just shove frames down a pipe, you'd need some way to communicate the frame rate/sampling rate, resolution, frame delimiters... once you've done all that you've basically recreated AVI. DOSBox only records audio that goes through its mixer, if you're using an external midi device the …

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Re: 64-bit dynamic_x86 (patch)

Posted on 2019-12-02, 01:49

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by jmarsh

in DOSBox Development

in DOSBox Development

Would be interested to see some before/after benchmarks for this patch: --- a/src/cpu/core_dyn_x86/risc_x64.h +++ b/src/cpu/core_dyn_x86/risc_x64.h @@ -468,7 +468,11 @@ static void gen_discardflags(void) { } static void gen_needcarry(void) { - gen_needflags(); + if (!x64gen.flagsactive) { + x64gen. …

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Re: imgmount

Posted on 2019-11-30, 23:17

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by jmarsh

in DOSBox General

in DOSBox General

Yes, the same filename shown when you use the DIR command inside DOSBox. (Or just type the first few letters of the filename and press tab to autocomplete it.)

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Re: imgmount

Posted on 2019-11-30, 22:36

by

by jmarsh

in DOSBox General

in DOSBox General

It works with either.

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Re: imgmount

Posted on 2019-11-30, 21:46

by

by jmarsh

in DOSBox General

in DOSBox General

A mounted drive only has short filenames.

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Re: I remember this as a kid "Cant delete files in dos - no room"

Posted on 2019-11-23, 01:35

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by jmarsh

in Milliways

in Milliways

The only way I could think of this happening is if you were using a strange version of DOS that always wrote directory changes to new clusters and then freed the old ones, instead of just overwriting them.

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Re: Darkspyre not loading

Posted on 2019-11-18, 03:03

by

by jmarsh

in DOSBox Games/Apps

in DOSBox Games/Apps

Those pictures refer to different files, C:\games\darkspyre\HORIZON vs. C:\games\darkspyr\disk1\HORIZON

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Re: How to enable Gravis Ultrasound on Doom

Posted on 2019-11-14, 01:03

by

by jmarsh

in DOSBox Games/Apps

in DOSBox Games/Apps

At some stage the article has been messed up and something has removed most of the backslashes from the text.

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Re: What to do when Windows 7 support ends in a few weeks time?

Posted on 2019-11-13, 06:32

by

by jmarsh

in Milliways

in Milliways

gdjacobs wrote: Pretty sure chains of trust don't need a network connection to validate as long as the chain is intact and present. They do if certificates can be revoked, which is the case for SSL.

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Re: x86 registers for emulating in a cross-platform way?

Posted on 2019-11-11, 01:07

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by jmarsh

in PC Emulation

in PC Emulation

I consider that confusing and obsfucated. Just use and and stick to uint16_t / int16_t etc. Completely agree, they are the "standard" types for a reason. when you talk about a byte or (double)word value, everyone that knows software knows what you're talking about, don't they? No. Is a "byte" …

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Re: x86 registers for emulating in a cross-platform way?

Posted on 2019-11-10, 22:43

by

by jmarsh

in PC Emulation

in PC Emulation

C guarantees the alignment of a type matches its size (at least for sizes up to the platform's natural word size). If you have a struct that has a uint16_t member followed by a uint32_t, padding is required to align the latter. The alignment of the struct overall will also be equal to the alignment …

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Re: Benchmarking DOSBox on latest machines

Posted on 2019-11-10, 22:31

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by jmarsh

in PC Emulation

in PC Emulation

Kerr Avon wrote: Have we reached the point yet where DOSBox, running on the most powerful PCs available to the public, can emulate games faster than they can run in real DOS on any machines? Not even close. Real DOS on a real P3 (maybe even P2) will outperform any machine running DOSBox.

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Re: x86 registers for emulating in a cross-platform way?

Posted on 2019-11-10, 15:04

by

by jmarsh

in PC Emulation

in PC Emulation

Not as long as the types are properly defined to the correct widths... It does seem a bit strange to have one type with the size in the name (uint_32), a very vaguely named "word" type and byte which is always 8-bits but isn't called uint_8. What is wrong with just using the stdint.h types?

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Re: x86 registers for emulating in a cross-platform way?

Posted on 2019-11-10, 02:45

by

by jmarsh

in PC Emulation

in PC Emulation

superfury wrote: Also, the packed part is to make it not add padding to each of the byte/word registers. That would cause trouble when using it? Padding is only added when a member doesn't fall on a boundary that is a multiple of its size. Where do you see that happening?

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Re: x86 registers for emulating in a cross-platform way?

Posted on 2019-11-09, 21:55

by

by jmarsh

in PC Emulation

in PC Emulation

Get rid of the packed specification. There's no need for it if the layout is correctly ordered.

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Re: Why does PhilsComputerLab disables all but 1 core on his XP gaming builds?

Posted on 2019-11-07, 22:35

by

by jmarsh

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some old games use multiple threads but since they were written before multi-core CPUs were around, they can behave not-as-designed when those threads run at the same time.

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Re: Null pointer dereferences

Posted on 2019-11-06, 20:43

by

by jmarsh

in DOSBox Development

in DOSBox Development

It's only undefined behaviour if the pointer is dereferenced. That's not happening here. Look up the definition of offsetof and see what it does.

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Re: Null pointer dereferences

Posted on 2019-11-06, 20:20

by

by jmarsh

in DOSBox Development

in DOSBox Development

No it's not. Members are always at a fixed location within classes. Under what situation do you imagine it returning random garbage?

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Re: Null pointer dereferences

Posted on 2019-11-06, 19:38

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by jmarsh

in DOSBox Development

in DOSBox Development

It looks like old code written to be portable before "offsetof" was widely available. It's not dereferencing a NULL pointer, it's getting the address of a member variable when the "this" pointer is NULL which is equivalent to finding the offset of that member (in bytes) from "this".

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