On Thu, 1 Mar 2001, Manuel Bilderbeek wrote:

> Another thing: your ROM image was only 16kB, while the SFG-05 is 64kB. How 
> come? Are you sure you got the full ROM image? (That ROM of yours does work 
> from fMSX by the way, but not properly: it restarts all the time. NOt that 
> surprising: a lot of hardware is missing.)

When doing ROM rips I like to be sure that I am getting exactly the right
size ROM. This is why I'm quite prepared to desolder ROMs and read them
out in an EPROM programmer. When I desoldered the SFG-01 ROM, I noticed
the text "16K ROM" on the pcb underneath the ROM. I also used my EPROM
programmer to read the ROM as if it were a 64K and 32K ROM. Only the first
16K was unique; higher addresses were repeats or not present at all; this
depends on whether the chip ignores the extra address lines or uses them
as chip select signals.

> I checked that 64kB ROM. IT seems the first 32kB is the same as the second 
> 32kB. If I run it with fMSX, the screen color changes and it crashes. Probably 
> because of the missing hardware. When I strip the second 32kB, it doesn't work 
> in fMSX:
> Found SFG05-cut.rom:
>   Cartridge A: FAILED
> 
> Does anyone have an idea?

This depends on where the ROM maps. With the SFG-01 it is quite
simple; the ROM maps into the first 16K of slot 3. However, if the SFG-05
ROM is 32K it is possible that the second 16K does not map directly above
the first but somewhere else. Another thing to note is that the sound
hardware overlays the ROM slightly; this is why you can't read all the ROM
from a working cartridge. It doesn't really matter, of course, but for an
accurrate record of the ROM I wanted to read it all so I desoldered it.


Richard


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