Re: 800XL question


Matthias Reichl wrote:
> On 25 Aug 2005 12:08:55 -0700, stephensheppard@xxxxxxxxxxx wrote:
> > Is it possible to use EEPROMs in place of EPROMs? If so which
> > type/size? Come to think of it, what size/type EPROM is used for the
> > 800XL?
>
> I'm using an AMD 29F010 (128k) flash ROM in my main 800XL. I've built
> a small adapter socket and connected 3 pins to switches so I can
> easily switch between max. 8 OSes (actually I use 2 switches, one
> SPDT and one DPDT with a neutral position plus two pullup resistors
> so I can choose between 6 OSes - this way I "loose" 32k but it's
> easier to select and I don't need 3 switches in my Atari).
>
> Instead of the AMD 29F010 you can also use a Winbond 29EE011 or an
> SST 29EE010 (these chips were often used on PC mainboards as BIOS
> chips, so if you have a dead PC have a look if you can salvage
> the BIOS chip). I've tested all three chips and they work equally
> well.

Hias, that is so cool and so creative!

>
> But: don't use a ST 29F010, it won't work well! Using it for an XL
> OS worked fine, but using it for the "old" (Atari 800) OS failed.
> I don't know what exactly is going wrong, maybe some access patterns
> put the chip into ID mode or something like that.
>
> Programming the flash ROM from within the Atari is not so easy. You
> would need some additional hardware to select the higher address
> lines, connect the /WE line, write a flasher program and completely
> turn off all interrupts and DMA while re-programming the OS.
>
> I programmed the flash using the new upcoming Turbo Freezer, but you
> can (of course) also use an EPROM programmer (just check out if these
> chips are actually supported, my old programmer didn't handle the
> AMD flash although it should have been supported).
>
> BTW: programming these flash chips is not too complicated, the
> algorithms are documented in the datasheets and all three chips
> are quite similar. My code also supports the AMD 29F040, a 512k
> flash ROM, which will be the default flash chip on the Turbo Freezer.
> So if you'd like to have 32 OSes in your Atari that's also possible :-)
>

Have you ever tried Uniflash for the PC?

On a working PC you hot swap the BIOS ROM then you use Uniflash to
flash whatever code you want to the chip. Well, that's theory, anyway.
I once tried it to recover from a failed flash but motherboard
differences and my unfamiliarity with Uniflash and flash ROMs led to
failure.

Thanks for sharing! This is exactly the kind of stuff I want to read
about.

Stephen Sheppard

.

Relevant Pages

  • Re: 800XL question
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