1Mb CHIP RAM hack and extra memory

orange · 28 June 2010, 19:49

What happens when you put 1,5Mb slowfast trapdoor RAM into A500 that has been 'hacked' to see 512k slowfast as CHIP?
(I am talking about the expansion that uses Gary chip)

Can you add a590 and have 1Mb Chip, 1Mb slowfast and 2Mb fast?

Zetr0 · 28 June 2010, 20:02

@Orange

Basically nothing sir,

basically after JP7A has been cut (EXRAM) there is nothing more to see on the expansion port, and the only access is done by the MUX'ing of the Agnus (JP2)

Any Ram placed into the expansion port will read as 512KB CHIP, even if you have 1MB populated on the board you wont see any more - this area *512KB is duplicated in both ram cells (the 512KB on the mobo and the 512KB on the expansion).

To get more FAST (SLOW) ram you will need trick GARY and re-assert the EXRAM (JP7A) on the motherboard - you will then need to create a small multiplexing circuit that MUX's addresses between 512kB extra Chip and the remaining RAM on the expansion -

- by far the better method would be to plumb for CPU Fast Ram, and use the modified board as simply as 1MB CHIP - and or, build a small MUXing circuit - Combined with an 8372B or 8375 (318069-xx) Agnus and using a piggyback chips on an A501 (for extra 1MB chip..

there are some plans for this on Aminet.

hope that lot helps.

orange · 29 June 2010, 09:31

ah, bummer.
what if i put the 1,5Mb expansion in A500+ ?

meega · 29 June 2010, 13:18

It ought to show as 2MB total chip, if you're lucky.

Ed: but might not work at all. The only things that should go in an A500Plus trapdoor is 512KB or 1MB chip ram expansion.

28 June 2010, 19:49	#1
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	1Mb CHIP RAM hack and extra memory What happens when you put 1,5Mb slowfast trapdoor RAM into A500 that has been 'hacked' to see 512k slowfast as CHIP? (I am talking about the expansion that uses Gary chip) Can you add a590 and have 1Mb Chip, 1Mb slowfast and 2Mb fast?

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28 June 2010, 20:02	#2
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	@Orange Basically nothing sir, basically after JP7A has been cut (EXRAM) there is nothing more to see on the expansion port, and the only access is done by the MUX'ing of the Agnus (JP2) Any Ram placed into the expansion port will read as 512KB CHIP, even if you have 1MB populated on the board you wont see any more - this area *512KB is duplicated in both ram cells (the 512KB on the mobo and the 512KB on the expansion). To get more FAST (SLOW) ram you will need trick GARY and re-assert the EXRAM (JP7A) on the motherboard - you will then need to create a small multiplexing circuit that MUX's addresses between 512kB extra Chip and the remaining RAM on the expansion - - by far the better method would be to plumb for CPU Fast Ram, and use the modified board as simply as 1MB CHIP - and or, build a small MUXing circuit - Combined with an 8372B or 8375 (318069-xx) Agnus and using a piggyback chips on an A501 (for extra 1MB chip.. there are some plans for this on Aminet. hope that lot helps.

29 June 2010, 09:31	#3
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	ah, bummer. what if i put the 1,5Mb expansion in A500+ ?

29 June 2010, 13:18	#4
meega Registered User Join Date: Dec 2007 Location: Oooh what a feeling yeaaah dancing on the ceiling Posts: 314	It ought to show as 2MB total chip, if you're lucky. Ed: but might not work at all. The only things that should go in an A500Plus trapdoor is 512KB or 1MB chip ram expansion.

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