A500 path to 2MB chipram?

[Xebec]

Hi folks!

What's the path to upgrade a NTSC Rev 5 A500 to 2MB of chipram? (My use case would be for WHDLoad + Vampire 500 V2+ .. to run all games).

I understand the 512KB --> 1MB path is:
A501 Trapdoor expansion (have this)
8372A agnus
+ some small modding of the mainboard
+ optional Denise

But to get to 2MB -- there used to be a mini/mega chip upgrade option? Is there anything else available ? Is there a 'simple' 1.5 MB path maybe?

Thanks!
John

[ajk]

For it to be simple, you do need the Mini Megi chip, or find yourself an A500+ (rev. 8) motherboard instead. It may be possible to hack a rev. 5 board with 2MB, but it's going to be fairly involved, as the older PCB designs simply aren't made for it.

[Xebec]

Originally Posted by ajk

For it to be simple, you do need the Mini Megi chip, or find yourself an A500+ (rev. 8) motherboard instead. It may be possible to hack a rev. 5 board with 2MB, but it's going to be fairly involved, as the older PCB designs simply aren't made for it.

A500+ would just need an additional 1MB via trapdoor ? (Assuming it came with 1MB on motherboard originally)

[ajk]

Yep, exactly. There are also plain A500s with rev. 8 motherboards, which can easily be upgraded to have 1MB on the board plus 1MB in the trapdoor. Of course the tricky part is you can't really tell the board revision without opening up the system

[Tyball]

I'm curious because I have a rev 8 myself, currently with 1MB chip: Are there a lot of OCS/ECS non-HD-installable games that require more than 1MB chipram for whdload?

[Jope]

I doubt there are any floppy runnable games that require more than 1MB of chip. Even 1MB chip games are quite rare.

[appiah4]

Originally Posted by Jope

I doubt there are any floppy runnable games that require more than 1MB of chip. Even 1MB chip games are quite rare.

>1MB chipram helps with WHDLoad significantly though, right? Things like SWOS don't run on 1MB Chipram IIRC. (Calling Galahad to maybe update the SWOS loaders to work on 1MB chipram )

[Jope]

WHDLoad slaves often do need more than 1MB. That's why I was careful to specify floppy runnable. :-)

[appiah4]

Originally Posted by Jope

WHDLoad slaves often do need more than 1MB. That's why I was careful to specify floppy runnable. :-)

Yeah but most are OK with Fast Mem + 1MB Chipram; WHDLoads that require >1MB Chipram are the exception IIRC?

[demolition]

In my experience, the late A500s which contains a rev. 8 MB often has the large badge (similar to A500+ badge) on the case like seen here:
http://www.nightfallcrew.com/wp-cont...d/IMG_0418.jpg

I have not seen any A500s with just the C= logo contain an A500+ MB, but of course that doesn't mean that it won't exist.

Rev. 6 can be upgraded to >1MB chip without too much effort using an A3000 Agnus but they quite hard to come by. Probably easier to find a MiniMegi chip upgrade but they are also expensive. It will be probably be cheaper to just get a real A500+ though and put a 1MB expansion in the trapdoor.

Since WHDLoad uses up a bit of chip mem by itself, the game it is running will not be able to use the entire chip mem in the system, thus it is generally nice to have >1MB.

[appiah4]

Originally Posted by demolition

In my experience, the late A500s which contains a rev. 8 MB often has the large badge (similar to A500+ badge) on the case like seen here:
http://www.nightfallcrew.com/wp-cont...d/IMG_0418.jpg

I have not seen any A500s with just the C= logo contain an A500+ MB, but of course that doesn't mean that it won't exist.

Well, my Rev 6A board with ECS Fat Angus and OCS Denise has the small C= logo, but room to solder on 512K extra chipmem. Rev 8 boards which are basically A500+ boards all have the larger badge.

Originally Posted by demolition

Rev. 6 can be upgraded to >1MB chip without too much effort using an A3000 Agnus but they quite hard to come by. Probably easier to find a MiniMegi chip upgrade but they are also expensive. It will be probably be cheaper to just get a real A500+ though and put a 1MB expansion in the trapdoor.

Since WHDLoad uses up a bit of chip mem by itself, the game it is running will not be able to use the entire chip mem in the system, thus it is generally nice to have >1MB.

I thought Fat Agnus could adress 1MB chipram without any modifications if you had a Rev 6 board?

[demolition]

Originally Posted by appiah4

I thought Fat Agnus could adress 1MB chipram without any modifications if you had a Rev 6 board?

Yes rev. 6 can be upgraded to 1MB chip by adding the missing chips and changing some jumpers, but if you want to have more than 1MB chip on a rev. 6 board, then you need to replace Agnus with the A3000 version since that is a 2MB Agnus with the same pinout. And Agnus 8375 from A500+ or A600 will not work since the pinout is different.

[appiah4]

Originally Posted by demolition

Yes rev. 6 can be upgraded to 1MB chip by adding the missing chips and changing some jumpers, but if you want to have more than 1MB chip on a rev. 6 board, then you need to replace Agnus with the A3000 version since that is a 2MB Agnus with the same pinout. And Agnus 8375 from A500+ or A600 will not work since the pinout is different.

Ok, sorry, I get it now

Maybe one day I will get around to trying this.. Out of curiosity, does the 1MB restriction on Rev 6 Agnus apply only to chipmem? Basically, if I upgrade the A500 to 1MB chipram, can the Fat Agnus still adress the 512K slow ram in the expansion port and give me 1MB Chip + 512K slow?

[demolition]

Originally Posted by appiah4

Basically, if I upgrade the A500 to 1MB chipram, can the Fat Agnus still adress the 512K slow ram in the expansion port and give me 1MB Chip + 512K slow?

I think that if you upgrade it to 1MB chip then you cannot have anything in the trapdoor, at least not without some bigger modifications. I am not 100% sure about this though.

[Zeph]

I think you would have to reroute the trapdoor mem somewhere else on the memory map?

[appiah4]

Originally Posted by demolition

I think that if you upgrade it to 1MB chip then you cannot have anything in the trapdoor, at least not without some bigger modifications. I am not 100% sure about this though.

Oh.. That kind of sucks, it would break compatibility with a lot of games I think. Sorry, I won't hijack this thread any further

[demolition]

Only some very early games require $c0 (slow) mem. Many of the affected ones were also later released in fixed versions so the problem is minor.

[E-Penguin]

The ACA500plus will put 512k in the trapdoor address range if you've remapped the real trapdoor to chip mem. I have this very set up working now (I cut the traces so the chip mem mod is somewhat permanent).

I bought a MegAChip expansion on ebay recently for about £75, they are out there if you look. I'm just waiting for a plcc extractor to arrive from China then I'll pop it in the A500.

[Xebec]

Originally Posted by Jope

I doubt there are any floppy runnable games that require more than 1MB of chip. Even 1MB chip games are quite rare.

I would assume 2MB of Chipram would allow you to use full ECS resolutions if you upgrade the chips (or use the Indivision upgrade)?

Also, I believe the run the newer AGA stuff with the Vampire accelerator you need a full 2MB of chipram installed.

Finally - out of 2,292 WHDload games, it looks like about 200 need > 1,024KB of chipram to run. with another ~ 200 needing exactly 1,024KB (which might be tough to achieve on a 1MB setup).
http://whdload.de/games.csv

[Xebec]

Originally Posted by E-Penguin

The ACA500plus will put 512k in the trapdoor address range if you've remapped the real trapdoor to chip mem. I have this very set up working now (I cut the traces so the chip mem mod is somewhat permanent).

I bought a MegAChip expansion on ebay recently for about £75, they are out there if you look. I'm just waiting for a plcc extractor to arrive from China then I'll pop it in the A500.

Just FYI on this - if you're thinking about a vampire upgrade later - it looks like the vampire won't fit with the megachip installed on an A500; but you may be able to use adapters to get around this. I was looking into megachips myself..

http://www.apollo-core.com/knowledge.php?b=5&note=2634