ISOCD optimisations (maximising memory for CD32 games/compilations)

[earok]

Hi all,

Boo Boo pointed out to me that you can gain a small amount of RAM when creating a CD32 ISO by tweaking the ISOCD settings. Not a great deal, but it can make all the difference between a game working and not working (eg Super Street Fighter II DX).

So I did some experiments to try and work out the optimal settings for a CD32 ISO (from a pure memory point of view - it probably adversely affects loading times but the loading times on SSF2 were just fine). These are my results.

To start with, I created a basic file structure just containing a C folder (with avail) and S (with system-startup, only containing a line to do an avail flush). Mounting it as a hard drive in WinUAE with CD32 config, it gave me the total memory of 1,916,544 bytes.

I then created an ISO of that file structure and loaded it through WinUAE. Memory was now 1,901,816 - a loss of 14,728 bytes.

Now, by fiddling with the ISOCD options I could make these gains:
Data Cache=1: 1,903,920 bytes, gain of 2,104
Dir Cache=2: 1,914,144 bytes, gain of 12,328
File Lock=1: 1,902,632 bytes, gain of 816
File Handle=1: 1,902,176 bytes, gain of 360

(These settings appeared to make no difference at all: PVDs, Retries, Direct Read, Fast Search, Speed Ind)

Combining all of these settings gave me a gain of 15,608 bytes, which is 880 bytes more than I had running from HD. So at least from this highly unscientific emulated study, it appears that running from a maximally optimised ISO is marginally more lean on memory than running from a Hard Disk!

If anyone can squeeze even more RAM out somehow, I'd love to hear from you!

[Whitesnake]

Lowering the Dir and Data cache to an absolute minimum will also give you slower loading times, The effect is not always greatly noticeable but some WHDLoad titles that require a good amount of OS Swapping can take up to 2m 30s to load e.g. 4D Sports Driving or Lotus 3.

But with enough cache enabled it will usually take less than 30s for a big game.

There is also a cumulative effect that occurs on the CD32, The more data on a CD the more memory is lost over time. I suspect this is because you can't prepare a disc image with 0 cache, So what happens is that 1k of Data Cache multiplies over time as the data in the disc image increases.

There isn't really much more you can do to increase the memory available on a CD32 unless an experienced programmer can clean out the remaining memory that is used by the extended rom and still keep the cd drive usable at the same time.

I believe that is how the RNC loader works for certain titles, I 'm not sure if WHDLoadCD32 works aggressively as that though, maybe it could be changed it if that isn't the case? You'd have to ask Wepl.

If it did clear out the memory like an RNC loader I suspect various John Twiddy games would start to work.

If you are really scratching for small amounts of memory you can try stuff like this but it is small.

Avail Flush
RemRAD Force
Assign ENVARC: Remove
Assign SYS: Remove
Assign C: Remove
Assign S: Remove
Assign LIBS: Remove
Assign DEVS: Remove
Assign FONTS: Remove
Assign L: Remove
Add36k

[earok]

Thanks whitesnake, much appreciated

[FOL]

Originally Posted by earok

Thanks whitesnake, much appreciated

Just to update this, you can also do this;

assign PRT: remove
assign CON: remove
assign RAW: remove
assign SER: remove
assign PAR: remove

assign PRT: dismount
assign CON: dismount
assign RAW: dismount
assign SER: dismount
assign PAR: dismount

This free's up more chip ram.

[gulliver]

You can also free some chipmem by running RemLib (from http://aminet.net/util/libs/IconLib_46.4.lha)

RemLib removes resident libraries from memory. Just be careful what functionality you loose when you remove a certain rom library. But for starters, icon.library should be pretty safe for removal in most cases.

[FOL]

Originally Posted by gulliver

You can also free some chipmem by running RemLib (from http://aminet.net/util/libs/IconLib_46.4.lha)

RemLib removes resident libraries from memory. Just be careful what functionality you loose when you remove a certain rom library. But for starters, icon.library should be pretty safe for removal in most cases.

I tried this, it wont remove any of the CD32 libraries / devices.