Date   : Sun, 21 Aug 2011 11:51:01 +0200
From   : rick@... (Rick Murray)
Subject: Tube ROM

On 19/08/2011 00:20, Alan Williams wrote:

> is almost certain to have done.  Filestores copy their entire ROM to RAM
> at boot before staring the OS and FS code up, so it clearly did by then.

I thought that was mainly because code and data were intermingled in all 
sorts of odd ways that would rather horrendously complicate the memory 
decoding?


> the fact that its too big for the socket it needs you to keep OE high
> during writes.

Indeed, it will be slightly more 'interesting' than bunging in a RAM chip.


> that the 6502 tends to do extra reads during instruction decoding

Ah... <expletive> Yes, I had forgotten that.

Question is, do the extra reads take place from near/at PC, or from the 
address pointed to?


> 29F010 should give 8 banks of sideways ROM each individually erasable.

Hmmm, I think the chip I have is a single 128K area.


> Presently I can read the device id.

'tis a start. ;-)


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...