Ultimem BLK6

Modding and Technical Issues

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polluks
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Ultimem BLK6

Postby polluks » Wed Dec 20, 2017 12:12 pm

Hi!
Does Ultimem support RAM at BLK6?

Greetings,
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tokra
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Re: Ultimem BLK6

Postby tokra » Wed Dec 20, 2017 12:40 pm

No, the VIC-20 (or more precisely the 6502 CPU) itself does not allow for RAM below ROM (like the C64 does). So you can just use the standard memory-areas that are unused in the VIC-20:

RAM1,RAM2,RAM3 ($0400-0fff)
BLK1 ($2000-$3fff)
BLK2 ($4000-$5fff)
BLK3 ($6000-$7fff)
IO2 ($9800-$9bff)
IO3 ($9c00-$9fff)
BLK5 ($a000-$bfff)

Of course the Ultimem can map it's huge memory pretty much any way you like to these areas.

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Re: Ultimem BLK6

Postby Mike » Wed Dec 20, 2017 12:51 pm

tokra wrote:or more precisely the 6502 CPU

In the C64, the PLA is responsible for the RAM/ROM mapping. That the mapping is (in part) controlled by the I/O port of the 6510 is more of an insignificant detail here.

The 'chip set' of the VIC-20 enforces a fixed mapping, how the internal ROMs (BASIC in BLK6 and KERNAL in BLK7) are set. No way to change that with an external cartridge, and - for that matter - there are no /BLK6 and /BLK7 signals present on the cartridge port, anyway.

I have a strong suspicion *why* you are asking this. ;)

If there was any easier way (i.e. without modification on the mainboard and preferably with some external cartridge) to achieve that feat, I'd have people know about this (same applies to my VFLI mod).

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Re: Ultimem BLK6

Postby groepaz » Wed Dec 20, 2017 1:54 pm

it would be so nice if you could map the e000-ffff block to ram as you can on c64.... but you cant :(

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Re: Ultimem BLK6

Postby Mike » Wed Dec 20, 2017 2:28 pm

groepaz wrote:it would be so nice if you could map the e000-ffff block to ram as you can on c64.... but you cant :(

It's not as if I hadn't entertained that idea once in a while - see the thread "WIP(?): A proposal for a VIC-20 with 60K RAM". That would also allow for RAM "under" the character ROM. With separated access paths for VIC and CPU.

Just my focus got devoted to other projects in the meantime. ;)

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Re: Ultimem BLK6

Postby groepaz » Wed Dec 20, 2017 3:51 pm

i like how that thread (once again) derailed =)

i am not really interested in solutions that involve modding the hardware though... obviously then its possible (or i could just pop a custom rom into it...) :)

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Re: Ultimem BLK6

Postby Mike » Wed Dec 20, 2017 4:13 pm

Of course it's not all that sensible to modify the mainboard if the intended result could also be achieved by an external solution.

That being said, my proposal in the other thread would have been 'nice to have', but on the other hand it had that smell of: "now that I've got the solution, I only need a problem". That's why I put that project on my low-priority list and ...

groepaz wrote:or i could just pop a custom rom into it...

... went for this route instead. :wink:

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Re: Ultimem BLK6

Postby eslapion » Wed Dec 20, 2017 5:18 pm

groepaz wrote:it would be so nice if you could map the e000-ffff block to ram as you can on c64.... but you cant :(

Well, it's possible with mods to the mainboard.
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Re: Ultimem BLK6

Postby groepaz » Thu Dec 21, 2017 8:10 am

what about "no interested in hw mods" was not clear? OBVIOUSLY you can achieve all kind of things that "do not work" by modding the hardware.

Of course it's not all that sensible to modify the mainboard if the intended result could also be achieved by an external solution.

i don't really like designing cartridges for specific things either :) i'd want to use stock setups, for vic20 probably even without using a floppy drive. the only hardware mod i find acceptable is RAM expansion (since those were incredibly common anyway).

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Re: Ultimem BLK6

Postby eslapion » Thu Dec 21, 2017 11:07 am

groepaz wrote:what about "no interested in hw mods" was not clear? OBVIOUSLY you can achieve all kind of things that "do not work" by modding the hardware.

Honestly, where ? The OP only said...
Does Ultimem support RAM at BLK6?

That would be 'no'. I don't see any post from the user asking the original question specifying he(she) is not interested in HW mods. It remains the only solution I know of. BTW, I know I wouldn't do it.

i don't really like designing cartridges for specific things either :) i'd want to use stock setups, for vic20 probably even without using a floppy drive. the only hardware mod i find acceptable is RAM expansion (since those were incredibly common anyway).

AFAIK, the vast majority of people using RAM expansion on their VIC-20 do it with a cartridge, not a hardware mod.
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Re: Ultimem BLK6

Postby groepaz » Thu Dec 21, 2017 2:17 pm

Honestly, where ? The OP only said...

you did not reply to the OP, you replied to ME.
AFAIK, the vast majority of people using RAM expansion on their VIC-20 do it with a cartridge, not a hardware mod.

thanks, captain obvious

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Re: Ultimem BLK6

Postby eslapion » Thu Dec 21, 2017 4:06 pm

groepaz wrote:you did not reply to the OP, you replied to ME.

I was replying to that specific post from you.

Overlooked this one 2 posts lower...
i am not really interested in solutions that involve modding the hardware though.

My mistake... :oops:
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polluks
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Re: Ultimem BLK6

Postby polluks » Thu Dec 28, 2017 6:41 am

Mike wrote:I have a strong suspicion *why* you are asking this. ;)

Nice try :)
I was thinking about a GEOS implementation but it would require a jump table at $C000 :(
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Re: Ultimem BLK6

Postby Mike » Thu Dec 28, 2017 8:50 am

polluks wrote:I was thinking about a GEOS implementation but it would require a jump table at $C000 :(

I'd suppose not having room for a jump table at a certain address would be the least problem in attempting a port of GEOS.

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Re: Ultimem BLK6

Postby polluks » Fri Dec 29, 2017 7:33 pm

Mike wrote:I'd suppose not having room for a jump table at a certain address would be the least problem in attempting a port of GEOS.

Not really, without this RAM area you will lose compatibility, see Apple II GEOS. Stupid design decision.
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