[BBC-Micro] Reversing the Tube ULA (destructively)
jumbos.bazzar at btopenworld.com
Tue Oct 26 15:52:25 BST 2010
----- Original Message -----
From: "Pete Turnbull" <pete at dunnington.plus.com>
> The original Tube ULA was made by Ferranti (part no 201,605). The
> second version is an AMD chip (2201,266) which isn't an exact
> replacement, nor is it pin-compatible. It's a CMOS device and was
> introduced when Ferranti ULAs became unavailable (to Acorn; they still
> had spares), in 1987. The third device is a daughterboard (0359,400)
> which has one of the AMD chips, three transistors, and about 10
> resistors, and is called the Bipolar Tube Emulator PCB. It was used as
> a replacement for the Tube ULA in most wedge co-pros, notably where the
> co-pro would work on a Beeb but not on a Master 128, because it's timing
> is a little different. However it wasn't recommended for use in ACWs,
> though I'm not sure why. IIRC it had problems with 32016 co-pros (eg
> Master Scientific).
> So if you're going to make a copy, I'd say copy the original ULA.
There is a third chip, made by AMS
It maybe a cousin of the AMI one, as both come from Austria it seems. I've
also not seen the one on the daughterboard, do you have a pic?
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