Date   : Mon, 05 Apr 2010 12:37:30 +0200
From   : kortink@... (John Kortink)
Subject: ReTuLa, a Tube ULA

On Mon, 05 Apr 2010 00:19:05 +0100, Phill Harvey-Smith
<afra@...> wrote:

>John Kortink wrote:
>> Okay, 'first silicon', so to speak :
>> 
>> http://web.inter.nl.net/users/J.Kortink/home/hardware/retula/retula_big.jpg
>> 
>> Outweighs the original at slightly over 10 grams,
>> yet lighter on the FIFO bytes ... More to follow.
>
>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.

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).

>Asuming you do get it going are you going to share the design ?

It's already 'going', Phil, working fine in ReCo6502, and
in both Acorn 6502 2p contraptions. And no.


John Kortink

-- 

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