Date   : Sun, 21 Aug 2011 17:17:12 +0200
From   : rick@... (Rick Murray)
Subject: 29F010 was Tube ROM but diverged.

On 21/08/2011 14:42, Alan Williams wrote:

> At the moment I have a 74LS139 and a 74LS00 the former doing the
> ROM/RAM/Motherboard selection from the page latch and the 74LS00 keeping
> OE high during writes.

Mmm, I'll have to check the datasheet for the 28F020 (IIRC, this is the 
one I have). Don't recall OE issues...

<looks for datasheet>

Mmm, it doesn't seem to do must with !OE, but it does some odd things 
with !WE for accessing the control regster...


> during writes so the 74LS00 is piggy backed.

Can't be as freaky as JGH's stack-of-ROM-sockets. ;-)


> It seems that they are the base address from which the effective address
> is being calculated.

Riiiight. Exactly the worst possible place.


> at any rate) that you could say you type *word to start View and if the
> machine had a View ROM then View would start but if it didn't view would
> load from your library directory on the server, copy its self to the
> sideways ram and start its self as a language.

Now *that* I like.


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...