Summary of required mods for audio to work in 7Mhz?

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Par Meits

Scribe (5532)

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05-10-2017, 11:55

Unfortunately the pitch is not an octave higher, but almost. This results in a very bad mix with (ie) Microcabin games. But as it is a constant, developers can circumvent the effect indeed Smile

I think I wouldn't want to have 4MB in my MSX as that gives some weird glitches once in a while.

Par msd

Paragon (1372)

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05-10-2017, 12:50

With turbo kits 7.16Mhz the z80 atleast has to be switched back to 3.58Mhz when accessing the VDP and diskrive. With most models other I/O works fine on 7.16Mhz. IIRC the msx-engine for example can run at 10Mhz.

The PSG should be fed with 3.58Mhz, I', not sure this is possible with the msx-engine without slowing it completely down.

Par Grauw

Ascended (8442)

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05-10-2017, 13:06

On the Panasonic turbo mode pitch is a perfect fifth higher. Pitch is directly related to the frequency relation; each doubling of the frequency gives a pitch exactly one octave higher. An increase of frequency by half, adds a perfect fifth.

7.16 MHz is double of 3.58 MHz, so exactly one octave higher. Similarly the Panasonic’s 5.37 MHz is exactly 1.5 times 3.58 MHz, due to the logarithmic scale you get a pitch offset of a perfect fifth (seven semitones). Note that a fifth on equal tempered scale is slightly off (by 1.955 cents), but for a replayer it’s a simple shift and add operation to correct for it pitch-perfect.

It is very rare to see frequencies on 8 bit computer hardware which do not have a simple multiplicative relation to 3.58 MHz...

I think the 4 MB issues are for the most part an urban legend.

Par msd

Paragon (1372)

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05-10-2017, 13:08

Quote:

I think I wouldn't want to have 4MB in my MSX as that gives some weird glitches once in a while.

big urban legend... Always had 4MB in my msx. Only the memory check of UR gave problems. But this due to bad software and not because of the 4MB.. Totally of topic Tongue

Par Grauw

Ascended (8442)

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05-10-2017, 13:15

For me too Unknown Reality is the only software I’ve ever heard of that has a problem with 4 MB.

And if you have less than that, you’ll miss out on a couple of nice VGMs that are larger than 2 MB Big smile. What would you rather have, patch UR to fix its specific problem, or get that stupid "out of memory" error and not being able to listen to music that you want to listen to Smile.

Par Meits

Scribe (5532)

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05-10-2017, 14:39

I've tested loads of software the last couple of months, just because I had too many doubles (doubles is an understatement). There were occasions where I needed much ram, so in went the 4MB mapper where later it had to be removed again. This was not UR. The software just didn't start. Don't ask me what program(s) it was as I don't remember. It's just that making it work after removing the large amount of ram did the trick.
Perhaps an urban legend, but there's practical proof of it Wink

An other (perhaps) urban legend is 192kB vram. I had this in the 90s, but had it made switchable back to 128kB as there was (at least) one piece of software that hated this. Too long ago to remember what it was, but not too long ago to remember that I did it and that there was a reason.

Maybe it'd be a good idea to write it down somewhere next time I (or someone else) runs into these issues Smile

Par Grauw

Ascended (8442)

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05-10-2017, 15:09

For sure Smile. Wiki seems a good place.

Par msd

Paragon (1372)

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05-10-2017, 15:49

@meits: There can be other reasons it didn't work which are not related to the fact that it is 4MB.
- Hardware corrupt
- Hardware interface not compatible with the msx you are using
- Power consumption

Par tvalenca

Paladin (728)

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05-10-2017, 16:59

Meits wrote:

I've tested loads of software the last couple of months, just because I had too many doubles (doubles is an understatement). There were occasions where I needed much ram, so in went the 4MB mapper where later it had to be removed again. This was not UR. The software just didn't start. Don't ask me what program(s) it was as I don't remember. It's just that making it work after removing the large amount of ram did the trick.
Perhaps an urban legend, but there's practical proof of it Wink

Could it be related to Moonblaster 1.4? (and not exactly to UR)

Par Meits

Scribe (5532)

Portrait de Meits

05-10-2017, 17:26

msd wrote:

@meits: There can be other reasons it didn't work which are not related to the fact that it is 4MB.
- Hardware corrupt
- Hardware interface not compatible with the msx you are using
- Power consumption

The 4MB issue software was tested in openMSX.
The 192kB vram issue was in a Jeroen Haisma (you know him) modded computer. He put the same switch in some other computers in my area as well... If only it wasn't 22 years ago I might've remembered that particular piece of software Wink

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