Re: Unaligned memory access and bus width

Posted on 2018-01-21, 20:30

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by Scali

in PC Emulation

in PC Emulation

I think the VGA latches simply respond to what address is on the bus. So unless you actually fetch a word or dword starting at A0000h or higher, VGA won't 'see' it. Having said that, there are indeed 'wraparound' issues when doing unaligned word/dword reads or writes at the end of a segment. I ran …

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Re: Unaligned memory access and bus width

Posted on 2018-01-21, 10:43

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by Scali

in PC Emulation

in PC Emulation

So for a 32bit load from offset 3 or 6 I see this: Offset 386SX(16bit bus) 386DX(32bit bus) ================================================= 3 4x16bit transactions 2x32bit transactions 6 2x16bit transactions 2x32bit transactions That's interesting though... apparently it can eliminate 2 redundant …

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Re: Unaligned memory access and bus width

Posted on 2018-01-20, 23:58

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by Scali

in PC Emulation

in PC Emulation

We have to treat ISA BUS differently. There is 8bit ISA and 16bit ISA. So by the time the request reaches the VGA card it is not in the form the CPU sent it. Those should be ok to be separated in byte accesses. I believe the a 16bit ISA VGA card can understand 8bit access vs 16bit access, but I am …

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Re: IBM Music Feature Card/Yamaha FB-01

Posted on 2018-01-20, 12:31

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by Scali

in DOSBox Development

in DOSBox Development

Hum, this may be more difficult than I initially thought... apparently Windows specifically splits MIDI input and MIDI output drivers. So I can't just easily add MIDI input to my existing FB-01Emu driver. No, it needs to become a 'dual-standard' driver, somewhat of a two-headed monster, so that it …

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Re: Unaligned memory access and bus width

Posted on 2018-01-20, 00:42

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by Scali

in PC Emulation

in PC Emulation

My understanding is that it is the other way around. That is, a 386SX still 'thinks' like a 386DX in terms of memory access. So it initially generates 32-bit accesses, which are then broken up into 16-bit accesses. Other than that, you can only have accesses of the size of your bus. So 8-bit …

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Re: IBM Music Feature Card/Yamaha FB-01

Posted on 2018-01-19, 16:25

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by Scali

in DOSBox Development

in DOSBox Development

I've reached the point where PlayRec sends the following SysEx command: F0 43 75 0D 20 00 00 F7 Then it waits for an answer (which never comes, since I have no actual MIDI device connected to answer this). The SysEx message appears to be an instrument dump message. I'm not entirely sure why PlayRec …

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Re: DreamBlaster S2P : Small form factor General MIDI on parallel port

Posted on 2018-01-19, 13:21

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by Scali

in Marvin \ Sound

in Marvin \ Sound

Unfortunately, many/most GM-supporting games run in protected mode via DOS4GW or similar, and the port-trapping technique used by SoftMPU won't work with those. SoftMPU was originally aimed at intelligent-mode MT-32 games which are all real mode. Virtualising ports transparently in PM is possible, …

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Re: IBM Music Feature Card/Yamaha FB-01

Posted on 2018-01-18, 23:18

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by Scali

in DOSBox Development

in DOSBox Development

I think I have the 8253 on the IMFC implemented. Apparently the IMFC uses a feature of the 8253 that I never noticed: each of the 3 counters can run on its own clock. Counter 0 runs on a 500 kHz clock. Counter 2 runs on a 2 MHz clock. Counter 2 runs in square wave mode, and its out is connected to …

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Re: MELTDOWN and SPECTRE vulnerabilities and older hardware?

Posted on 2018-01-18, 22:47

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes. I shouldn't use word branch. It is reserved for Spectre flaw... But it really is irrelevant because those flaws are very similar. Manufacturers assume that nobody check that in fact modern cpu do not check memory operation BEFORE doing speculative execution. The whole point of speculative …

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Re: MELTDOWN and SPECTRE vulnerabilities and older hardware?

Posted on 2018-01-18, 21:26

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

First Meltdown is really Intel hardware flaw. In essence, to allow speculative execution to take that branch of the code which step up on kernel memory when processor is into user mode and running unprivileged process is unacceptable error of implementation of their own architecture. Simply that …

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Re: 8086 clones with more than 1MiB of addressable RAM ?

Posted on 2018-01-18, 10:27

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by Scali

in Milliways

in Milliways

There is at least one NEC V-series chip that can address 16MB. One of them is the V33A. It has 24-address lines, and it's an extended 8086. Ah yes, here is its datasheet: http://datasheet.datasheetarchive.com/originals/scans/Scans-107/DSASCANS15-59629.pdf Apparently they've created a new mode where …

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Re: MELTDOWN and SPECTRE vulnerabilities and older hardware?

Posted on 2018-01-18, 00:34

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

bjwil1991 wrote: Checked my Pentium 4 IBM ThinkPad R40 and it's vulnerable 🙁 The OS may be, CPU is inconclusive, see above.

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Re: What retro activity did you get up to today?

Posted on 2018-01-17, 22:48

by

by Scali

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've been refactoring the DOSBox code so that the PIT code now has a reusable base class for generic 8253/8254 emulation, at any given base clock. Why? Because the IBM Music Feature Card also uses an 8253 PIT, but running at 1 MHz instead of 1.19 MHz. So far I've made DOSBox work with Timer, which …

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Re: DreamBlaster S2P : Small form factor General MIDI on parallel port

Posted on 2018-01-17, 12:15

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Also, the serial port competes with many other peripherals that could be useful for gaming whereas the LPT is basically redundant and always available. Also, I previously described a way to connect up to 256 ports to a single LPT. If you put two 8-bit latches on there, you can use one for address …

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Re: DreamBlaster S2P : Small form factor General MIDI on parallel port

Posted on 2018-01-17, 10:28

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

can't you already have that with softMPU's serial function and a module that has serial port like the SC55-mk2 or MU-80 for example? Yes, but the 'serial port' bit is rather limiting. A standard MIDI output and/or wavetable header would allow you to use any MIDI device. Even a Yamaha FB-01, for IBM …

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Re: DreamBlaster S2P : Small form factor General MIDI on parallel port

Posted on 2018-01-16, 21:02

by

by Scali

in Marvin \ Sound

in Marvin \ Sound

Yeah that could be done, but does it make sense ? I guess you'd basically end up with MPU401-over-LPT. Which is more or less what the DreamBlaster S2P does, except in this case you would need to add the synth yourself. Not sure what the target would be exactly. Systems that have parallel ports, but …

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Re: DreamBlaster S2P : Small form factor General MIDI on parallel port

Posted on 2018-01-16, 19:36

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by Scali

in Marvin \ Sound

in Marvin \ Sound

Wouldn't it in theory be possible to use wavetable daughterboards and/or MPU-401 devices in a similar fashion? Not as-is. The Dream chip used on this device has a parallel MIDI interface. Wavetable is serial (basically standard MIDI, with a different connector). So you'd need to add a UART between …

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Re: TNDLPT : Tandy Sound on parallel port

Posted on 2018-01-16, 17:51

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by Scali

in Marvin \ Sound

in Marvin \ Sound

matze79 wrote: Some Idea raises into my Mind... theTandlib .. Combines Adlib and Tandy 😁 on one ISA Card. The ultimate ISA sound card... OPL3, CMS, SN76489, MPU-401, wavetable header and joystick...? 😀

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Re: IBM Music Feature Card/Yamaha FB-01

Posted on 2018-01-16, 16:45

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by Scali

in DOSBox Development

in DOSBox Development

That first build of SoftIMFC was massively bugged. I now have a proper way to test it, via the DreamBlaster S2P. I got it working on that, tested with Laura Bow, Larry 2 and Larry 3. It should also work fine with an MPU-401, but I don't have a machine to test it on. Here it is: https://www.dropbox. …

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Re: 8086 clones with more than 1MiB of addressable RAM ?

Posted on 2018-01-16, 14:15

by

by Scali

in Milliways

in Milliways

Yes, the segment + offset addressing scheme of the 8086 is physically limited to 1 MB. The only backward compatible way around it is via virtualization, which requires a 386+ with v86 mode. You can then create separate 1 MB address ranges for each process on the machine. The same trick is still …

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