Memex Chameleon

[Pernod]

Anyone know anything about this?

As usual, I'm specifically looking for the ROM that came with it.

[julians]

Anyone know anything about this?

Memex Chameleon 256K Board - ROM 2_00 (2764).zip

(3.35 KiB) Downloaded 43 times

As usual, I'm specifically looking for the ROM that came with it.

Yes I do - my original Beeb had one.
Here's the ROM.

Julian.

[Pernod]

Yes I do - my original Beeb had one.
Here's the ROM.

Julian.

Very nice, thanks Do you still have the board that you can provide photos of, and any documentation for it? A quick look at the ROM suggests it contains a RAM test which should help to understand how it's implemented.

You seem to be finding rare and unusual items recently, looking forward to seeing what else you may produce

[julians]

Very nice, thanks Do you still have the board that you can provide photos of, and any documentation for it? A quick look at the ROM suggests it contains a RAM test which should help to understand how it's implemented.

You seem to be finding rare and unusual items recently, looking forward to seeing what else you may produce

I did have the manual, although it may have gone missing... Might take a while to work my way to my BBC books and stuff but I do intend to.
Finding rare and unusual items? Only ever the stuff I'm not actually looking for!

Here's some pictures - not sure if they'll be good enough to give you need, but if they're not just ask.

The connections to my very crusty looking Beeb aren't too clear tbh, but it's:
Yellow - mid position S20
Grey - south west S21
Blue - mid position S22

Julian.

[lurkio]

Here's some pictures

Nice! Does the board still work? Do you remember what you used to use it for?

[Pernod]

I should be able to work out how it works from doing a *RAMTEST:

I wonder whether the normal Beeb ROM sockets are mapped 0-3 or 12-15?

[julians]

Nice! Does the board still work? Do you remember what you used to use it for?

It did last time my old Beeb was turned on, although that was at least ten years ago and my old Beeb was temperamental to say the least - pretty much everything in a socket needs a good wiggle for it to start up.
I used it as a shadow and sideways RAM board and it worked really well for that - I vaguely remember tinkering with the multi-tasking, but IIRC (and I might not be) it technically worked, but didn't really practically work quite as well as it could although all of the finer details escape me currently. I'm guessing swapping OS, language and FS working space around wasn't really something any of them expected...
I can't remember how the RAM or ROM sockets were mapped and I've dug out a few of my old working disks and not a single one makes a reference to a sideways RAM back when loading a ROM image, so that's not much help. If I'm feeling brave tomorrow I'll see if my old Beeb will play nicely and work, rather than play dead or pop something in the PSU.
I did find a disk labelled 'ADE plus v 0.93 (pre release)' - doubt that was the exciting or rare stuff you were hoping for though!
I can't remember what I paid for it BITD but I doubt it was more than half the price of the advert you've referenced.

Julian.

[Pernod]

I did find a disk labelled 'ADE plus v 0.93 (pre release)' - doubt that was the exciting or rare stuff you were hoping for though!
I can't remember what I paid for it BITD but I doubt it was more than half the price of the advert you've referenced.

Julian.

Whilst ADE plus may not be that exciting, it's definitely rare so worth archiving.

I don't remember hearing about the Memex BITD and only stumbled upon the advert recently whilst looking for obscure things to emulate. Doubt they sold many, probably due to more popular alternatives from Aries and Watford. The multi-tasking element sounds unique though.

It's implementing additional latches at &FE31, 34, 35 which I'd hope to see documented in the manual. Emulating the sideways RAM part should be fairly obvious, the shadow and multi-tasking not sure yet.

[julians]

I wonder whether the normal Beeb ROM sockets are mapped 0-3 or 12-15?

They appear in their usual locations with the board plugged in, although are duplicated in 8 through 11 and prefixed with a $ - although my memory is failing me about the significance of that. Time to try and find the manual....

Julian.

[Pernod]

I wonder whether the normal Beeb ROM sockets are mapped 0-3 or 12-15?

They appear in their usual locations with the board plugged in, although are duplicated in 8 through 11 and prefixed with a $ - although my memory is failing me about the significance of that.

The $ probably just indicates it's mirrored, my emulation shows the same. I also have *RAMTEST working now with no errors, though it only seems to test the 128K used as sideways RAM.

The latch at &FE31 selects a bank in the same way as &FE30, but makes it writeable. So address line A0 is being used as a software write protect switch.