On Thu, 18 Mar 1999, Maarten ter Huurne wrote:
> Lots of people have one. I am one of them.
> Philips 8235, 8245, 8250, 8255 and 8280 were all sold with 128K mapper.
Only Philips did it? Did other manufacturers do only 256kb of Mapper
built-in?
> >Beyond Metal Gear 2, do you know other Megarom games with 512kb of more?
>
> Hydlide 3 is 512K.
> ROM version of Royal Blood is 1MB.
8-megabit Megarom??? That's impressive! Is it downloadable in any site?
> >And nobody was interested in transforming MSX1 to MSX2?
>
> I don't think any company ever offered such a conversion. Conversions from
> MSX2 to MSX2+ were offered though. Some included only V9958, others
> included new ROMs and/or internal MSX-MUSIC.
Here in Brazil the only way to get MSX2 was doing conversions! Only
actually Ademir Carchano produces boards of MSX2+, previously all MSX2 and
MSX2+ were converted from MSX1.
> >But ROM cartridges are very expensive. A memory expansion with exactly the
> >same format than Megarom games was a more intelligent solution than buying
> >several cartridges. Why didn't people from Japan create a kind of Megaram?
>
> Maybe they don't like doing illegal things?
Take it easy! I was talking about one manufacturer (for example, Konami)
sells Megaram cartridges and sell disks with the games separately. This
would be much cheaper.
> Anyway, they did finally create one: the ESE-SCC. But it's main use is as a
> RAMdisk/DOS2 cartridge.
That's a good idea, but was made very time before the Megaroms cartridges
had been manufactured.
> The reason MegaRAM type cartridge was never developed in Europe is probably
> that 128K and 256K machines (SONY700) were sold. A lot of people had their
> MSXes memory expanded to run cracked megaROM games.
Ok, that really explains everything.
> >There was another problem here in Brazil (and perhaps in Europe too):
> >there was no japanese softwarehouses representatives here! What were we
> >supposed to do?
>
> In Europe, for a long time software was available in normal stores. But
Was Japanese software available in normal stores?
> around 1990 we had to rely on imports for games like SD Snatcher and Solid
> Snake. I guess the European market was not profitable enough to make
> English versions of those games. One of the reasons was the large-scale
> copying.
Importing games? Wasn't it too slow and too expensive?
> >Do you know a FDC that supports 1.2Mb and 1.44Mb drives and is still being
> >produced, and have good documentation?
>
> Note that 3.5MHz is too slow to allow reading of 1.44MB disks. The "inner
> loop" of the sector read routine is too slow to cope with the data flow. So
> if you want to create 1.44MB drives for MSX, you either have to use 7MHz
> Z80 or use some kind of buffer for reading sectors.
Are you sure? A 720kb disk works with a FDC that handles 250kbits/s, a
1440kb disk works with a FDC that handles 500kbits/s. This means that the
main routine should be able to read 12500 bytes per turn. It means that
this routine should run 12500 times in 0.2 seconds. Then, the routine
should spend a maximum of 16 microseconds. In a 3.57561149MHz, this means
57 clockcicles.
LD HL,address
LD C,D3h
LOOP: IN A,(D0h) ; 12 clocks
RRCA ; 5 clocks
JR NC,LOOP ; 9 or 12 clocks
RRCA ; 5 clocks
RET NC ; 9 clocks
INI ; 21 clocks (I guess)
JP LOOP ; 10 clocks
Total: 71 clockcicles. Conclusion: you're right, it's not possible to use
1.2Mb or 1.44Mb disks with Z80 at 3.57MHz. It's BAD!
Then, there's still a chance only for Turbo-R.
Greetings from Brazil!
-----------------------------------------------------------------
Marco Antonio Simon Dal Poz http://www.lsi.usp.br/~mdalpoz
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