A501 expansion

[craggus2000]

hi Everyone,

Whist I've been reading on the EAB forum for quite a while, I've only just registered to be a member here, so this is my first post!
First have to say excellent source of information and resources....

My question is relating to the A501 RAM expansion (or indeed any RAM expansion for the A500): Can any of these be modified to work in an A500plus? As I read they have a battery and some other stuff which the A500plus does not a require as it has these on its mainboard.

Ideas and guidance is greatly appreciated!

[AndyLandy]

I believe you can plug an A501 into an A500+, it'll appear as 0.5MB of Chip RAM and the clock will be ignored.

[craggus2000]

Are there any other RAM expansions of 1MB that will work in an A500plus?

[rkauer]

I may say there is around 20 different 1Mb RAM boards available for the A500+.

You can see those here: http://bboah.amiga-resistance.info/index_e.html

[Zetr0]

@craggus2000

The A500+ is dumb port (like the A500) - however unlike the A500 it is configured to assert upto 1MB of memory found in the port as CHIP RAM - giving you 2MB of precious CHIP ram to violate with your favourite games.

Now, any 512KB memory adapter will work in an A500+ (giving you 1.5MB of CHIP) the same cannot be said for some A500 1MB adapters; While I suspect that a 1MB A500 adapter attached to the Trapdoor Port may infact give you another 1MB of CHIP - its not a garantee -

Some A500 1MB Adapters use two banks of memory - multiplexed by re-routing some signals from GARY - so its equally likely that the 1MB Adapter may only function as a 512KB upgrade in an A500+

However all is not lost - its relatively simple to upgrade (hack) a Rev6 A501 to an A501+, now when I say simple - that also means a little labourious as you have to piggy back 4 chips - and solder some wires between them and then to a point on the card.

I promised myself to make one of these as they are quite simple to do - infact it would be cool to do the A500+ Tabajara hack eh rkauer? =D.

infact I think the A500+ is a lot easier to do - its all on one side!!!!


anyway have a lookie here at trapdoor port CHIP/RAM upgrades - remember with the exception of 512KB upgrades - if it doens't say A500+ its not likely to be compatible.

[craggus2000]

Originally Posted by Zetr0

its relatively simple to upgrade (hack) a Rev6 A501 to an A501+, now when I say simple - that also means a little labourious as you have to piggy back 4 chips - and solder some wires between them and then to a point on the card.

This sound like a bit of fun . Do you know where I can find the instructions? (been looking to no avail )

Originally Posted by Zetr0

it would be cool to do the A500+ Tabajara hack eh rkauer?

Found the Tabajara for A600, are there any plans/instructions for A500+?

Thanks

[Zetr0]

@craggus

my friend, its not been made yet - you will need the A500+ schematics of the trapdoor port - very closely resembles the A600 port in the sense that its a dumb port.

download this Amiga Schematics Archive - in this archive is an A500+.pdf (about 7MB) - you want page 8 of this.

This will detail the Expansion port - from this you should be able to reference the following

Data Lines
Address Lines
RAS (Row Address Signal)
CAS (Column Address Signal)

I believe that you will need some pull down resistors to hold some signals low so that it asserts the CHIP RAM as a full 1MB

Again this is somthing I promised my self I would do - sometime - but there always seems to be beer and curry in the way..... damn it!


modding/hacking an A501 might be easier BUT you will have to remove the logic off the card and re-route ..... yeah yeah.... sounds tricky - but not if you draw it out on paper first.

I like a Nice A3 or if I am felling VERY creative an A2 piece of paper (or half a tree in the case of A2) and gently detail all the components - failing that I find M$ paint works well.

[craggus2000]

@Zetr0

Thanks for the info, I've just bought one