do you know dhryston.com , how does your msx score ?

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Basicly atm its like removing the Z80 put in the new and solder two wires, some MSX computers need an adaptation on the mainboard. New resister array for the keyboard and some rerouting to the engine.

If you need some resistor arrays? I ordered 100 of them
There not expensive

@SMDNearDark

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With only the CF interface 8,8mhz is working.

Do you try with cartridges that use the "clock" signal?

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Basicly atm its like removing the Z80 put in the new and solder two wires, some MSX computers need an adaptation on the mainboard. New resister array for the keyboard and some rerouting to the engine.

What about rerouting to the engine? can you explain it?

thinking it twice the only way to work around the 3.5Mhz or 7-8Mhz
limitation on memory & i/o bus and have a z80 running at much higher
speed is :

execute one instruction per cycle like r800
and/or
having cache : so loop speed would be increased.
only read cache would be good enough.

but all this is only possible on fpga...

@SMDNearDark
which msx model do you use?
have you got schematics about your upgrade?

Just one idea:

Use a counter to divide VDP base speed by 2 or 4 and obtain a CPU speed of 10,738635 Mhz or 5,3693175 Mhz.

MSX1 VDP speed is 10,738635 and MSX2 is 21,47727 so, if a switch is added to adjust speed divisor, any of the above speeds can be reached.

Mainboard clock should remain unmodified to avoid I/O and PSG malfunction.

Will it work?

I never understood what was the need to overclock the MSX
Every software ever written for it was for the 3.5MHz Z80 ...
What's the use ?

Almost every software is based on that 3.5MHz speed.
Going faster is just to make a mess on the screen ...

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@SMDNearDark which msx model do you use? have you got schematics about your upgrade?

SMD uses a Philips NMS8220... it's quiet around the project atm, but I'm sure he/we will pick it up soon.

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I never understood what was the need to overclock the MSX Every software ever written for it was for the 3.5MHz Z80 ... What's the use ? Almost every software is based on that 3.5MHz speed. Going faster is just to make a mess on the screen ...

The point of speeding up the MSX has imho the most effect with mass storage devices... load and read times are much shorter at 7/8Mhz than with 3,5Mhz.

In general an overclocked MSX produces no mess on the screen, because the speed switches back to normal on vdp access. The sound is in most cases too fast and horrible to listen to.

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I never understood what was the need to overclock the MSX Every software ever written for it was for the 3.5MHz Z80 ... What's the use ?

That's not entirely true. Many games seems to be designed to run at 5.37MHz. It's pure speculation, but it indeed does look like the developers used turbo boards to speed up the development and did end up testing the game @ 5.37MHz too.

Almost all Konami SCC games drop frames constantly when run @3.57MHz. Unfortunately many of those also do have a bug in the timing routine that allows the game to run at twice the speed if the Z80 clock is higher than 5.37MHz too.

That's why I'm slowly fixing them. On my website you can get the patches and the games that are already turbofixed. It's a lot better to play them with the turbo enabled:
- No more slowdowns
- Less sprite flickering

I personally recommend you to try the MG2, Gradius-2 and Salamander fixes to see the benefits I'm talking about.

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Almost every software is based on that 3.5MHz speed. Going faster is just to make a mess on the screen ...

Not true also. Many of the MSX games have timing routines synced with the VDP interrupt. When properly coded like this, the games do accept any CPU speed and will work much better with the turbo enabled, like:

- Guardic
- F1 Spirit
- Penguin Adventure
- etc (for a more complete list, have a look at my website)

Unfortunately some games do have trouble with the turbo, but this is easily fixable:
- Games that use the MSX-Music (aka FM-PAC). The game itself may run properly, but the YM2413 music gets all messed up (I.e.: Aleste, MonMon Monster)
- Game badly ported from the ZX-Spectrum: Those will have no timing mechanism at all. But the bad ports also cause a lot of trouble with other aspects of the MSX architecture, like expanded slots or the MSX-DOS2. (for properly ported ZX-Spectrum games, have a look at Amusement Factory's website. A proper port of any spectrum game shoud REQUIRE the turbo, since given the architecture differences between the two, the MSX version will require at least a 5.37MHz CPU to run at the same speed the ZX-Spectrum did.
- Games with bugged timing routines: This is the most common case you'll find. It's easily fixable. Sometimes the timing bug only do affect the intro (I.e.: Space Manbow, Quarth)
- Games with timing on some parts and lack on others. Mostly, the only affected part is the intro (I.e.: Valis 2, Daiva-5)
- Games without timing routines. (I.e.: Warroid, Theseus, Redzone). Those will really run wildly fast and make a mess on the screen. Fortunately those are also easily fixable.

Can we haz pic and price plz?

There are no prices available yet... it still has to be tested thouroughly.

Having more speed is always a goog think, unfortunately the msx lacks a good engine for syncing access to others devices, so VDP accesses are messed up with a faster clock. Only TR has a timing engine.

I make my own 7mhz kit to my vg8235 msx mod and works fine.
"fast dir" with lots of files (fat16)
sound is not correct (as expected)

z0858110psc IC is hard to find.

http://www.flickr.com/photos/44218601@N06/sets/72157623366903040/

usuario: can you please publish plans in English to HansO? Thanks a lot