> 3. Compression
>
> TRD said storage capacity is cheap nowadays, so we don't have to use
> compression. I don't agree, for a couple of reasons. For one thing, not every
> file is a 16K ROM. MegaROMs are often 128K or 256K, some as large as 2MB. If
> we include disk games as well, games of several megabytes exist. Having a
> couple of hunderd games on your harddisk, the space does add up. And on a
> real MSX storage size matters a lot more. The second reason is that network
> capacity is not nearly as large as storage capacity, so we should also think
> about download times and bandwidth use.
>
Download times? Are the ROM / DSK etc. not already packed with zip/lha/lzh/pma when
you download from internet today?
Well if we are talking of implementing this standard for DSK images/ other file based
games too I agree that the compression would save some space.
But this will only apply to emulators.
I agree on the fact that the 128K/256K ROMs take MUCH space on msx´s floppy disks /
harddisk but decompression speed on msx is too low for such operation (unless you
don´t care about the speed). It would take ages to load anything. How do you imagine
to decompress 128K/256K ROMs on msx? It would only apply to people with harddisks.
So mainly this compression issue is merely to be used only with emulators.
> LZW is not a good choice: it is covered by a patent and the patent holder
> (Unisys) won't allow compressors without a license. This caused the problems
> with the GIF format.
>
> ZIP-inflate and GZIP (is that the algorithm's name, if not, what is?) are
> free and already implemented. Does anyone know what is the status of the LZH
> algorithms ("-lh4-"/"-lh5-") and the PMA algorithm ("-pm2-")?
>
> My concern is that some of the algorithms may be slow on real MSX, or require
> much memory while unpacking.
Well as said before it´s better to forget about implementing any decompress&run for
packed rom files on real msx.
An individual decompression routine for MSX would be enough, to manually decomress /
extract the files.
- It would be nice if for example 32K ROM files
> would run on 64K RAM machines. After the loader code and the system RAM, that
> would leave about 16K of memory for the unpacking algorithm. Can anyone tell
> us how much time and memory each compression algorithm takes?
>
There is somewhere a ROM to COM converter.
After that it could be compressed with POPCOM but if it will work or not dunno.
Just a suggestion :-).
> Although the PAC SRAM can be shared by many games, this is not a good idea.
> The user must remember which blocks are in use by which games, and many games
> don't even allow to user to choose the SRAM block but use a fixed block
> instead. It's a lot easier to use a separate PAC SRAM for every game.
Just a question:
Is there a difference between the SRAM in PAC /and FM-PAC cartridge????
Greetings from Bjørn Boye Skjoldhammer
How to contact? See: http://www.geocities.com/msxtrd/data.html
ICQ #20449307
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