Date   : Mon, 05 Apr 2010 12:08:37 +0100
From   : afra@... (Phill Harvey-Smith)
Subject: ReTuLa, a Tube ULA

John Kortink wrote:
> On Mon, 05 Apr 2010 00:19:05 +0100, Phill Harvey-Smith
> <afra@...> wrote:
> 
>> Humm, unless I'm not really understanding things isn't a 64 macrocell 
>> CPLD a little small to implement the tube ULA ?
> 
> Only to implement all 20 'VDU FIFO' bytes.

Ok perhaps I should have said full tube ULA.

> But even with just one byte, pumping VDU data through at
> full speed is, in practice (e.g. back-to-back character
> printing, Tube Elite), only a 3 to 4% performance hit.
> 
> The design takes a 128 macrocell CPLD as well, so there's
> still room for a handful of VDU FIFO bytes, if necessary
> (although not all 20).

Ahh ok then. My own experements had come to this conclusion, actually 
with some re-jigging of the code either end you could probably get away 
with one byte in each direction.

>> Asuming you do get it going are you going to share the design ?
> 
> It's already 'going', Phil, working fine in ReCo6502, and

Phill << Please note correct spelling.

> in both Acorn 6502 2p contraptions. And no.

Ahh so another closed design, with a single point of supply so the 
community is no better off in the end.....

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.