[BBC-Micro] Reversing the Tube ULA (destructively)

Ed Spittles percy.p.person at gmail.com
Tue Oct 26 23:28:00 BST 2010

Hi Everyone,
  replying mostly to the earlier messages...

On 26 October 2010 00:14, Theo Markettos <
list-a_cloud9.bbc-micro at chiark.greenend.org.uk> wrote:

> We have suitable microscopes, though fuming nitric acid is Frowned Upon
> by the university health and safety people and I'm not trained with it.
>  But
> if anyone can do the depackaging (and I can tell you what to do) then I can
> image it.

That's great!  I see that acetone for the plastic and violinist's rosin for
epoxy is supposed to work
(http://s3cu14r.wordpress.com/2010/07/15/boiling-chips-in-tree-sap/)  - has
anyone tried it?

On 26 October 2010 01:46, Philip Pemberton <philpem at philpem.me.uk> wrote:

> It might be worth sending a chip to one of the professional decapping
> services, like MEFAS:

Good idea - if it's cheaper than posting to California.

On 26 October 2010 02:34, Jules Richardson <jules.richardson99 at gmail.com>

> Ed Spittles wrote:
> > Even more ideally, someone already has some high-resolution photos of
> > the chip, or the original artwork...
> Hmm, anyone know who had a hand in the design

I think Sophie Wilson did some or all of it: I'll ping her

On 26 October 2010 02:34, Jules Richardson <jules.richardson99 at gmail.com>

> Also, is it *that* hard to reverse-engineer and produce a pin-compatible
> equivalent? (maybe a smaller IC of some form on a carrier board?) Why the
> need
> to try and clone the actual chip from visual inspection - simply for
> curiosity? (A noble enough reason ;)

Curiosity is part of it, but also accuracy.  Several people have built a
design from observations and documents: Sprow, John Kortink, beeb816
team(*), and at least one other. But are they completely bug-compatible in
all coprocessors on all tubes in all hosts?  And how much effort to find
out?  I think neither John nor Sprow have released their sources, although
John has shared some tips.

(*)http://sites.google.com/site/beeb816/hardware/tube-on-fpga - is open
source, still a work in progress. Mark and Richard are collaborating right


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