It seems that these files will work if programmed into a
27C512, or if they are programmed into the *TOP* half of a 
1 Meg EPROM.

I haven't confirmed that a 27C512 will work, but since pin
30 of the 32 pin socket, which is pin 28 for the 27C512, is
tied to VCC, then it should be fine.

So why did Akai use 1 Meg EPROMs?

- - -  

Below is what I wrote in March 2000.

These files:

  4_30_LSB.EPR
  4_30_MSB.EPR

are raw binary files read from 27C1001 EPROMs.  

They are the 4.3 operating system for the S1100.
This is the final release from Akai.

I don't have an S1100 schematic, only an S1000 schematic,
so I haven't investigated the exact select line situation
with these EPROMs.  

There seem to be two flavours of 1 meg EPROMs:

   27C1001  (the same as a 271010?)

   27C1024

There may be programming differences between all these types.
The datasheets I have to hand indicate that the 27C1001 has
the following characteristics:

Pin  1  VPP  (High or low during read.)  High in the S1100.
Pin  2  A16                              

Pin 30  NC                               High in the S1100.
Pin 31  /P   (High or low during read.)  High in the S1100.
Pin 32  VCC

Apart from that, it is much like a 27512:

Pin 22  Output Enable active low.
Pin 24  Chip Enable, active low.

Robin Whittle   http://www.firstpr.com.au   15 March 2000


