Re: 1541IDE and 1541IDE-S -- and 8250IDE? (and 64IDE, now)

From: Nicolas Welte (
Date: 2007-12-22 20:36:30

Hello all,

I just started browsing through this subject and all its sub threads :)

A very interesting project, I'm curious where this will lead to! wrote:
> But for programmers with two left hands regarding soldering, it is ideal
> :) And another tip: use Nicolas Welte's 6502 board to expand your 1541
> with extra ROM and RAM.

thanks :)

> Regarding the 8x50: the ROM for the FDC resides inside the 6530. I
> haven't found time yet to find out if the I/O of the 6530 is needed when
> using a harddisk. If not, the needed EPROM can be stuck on the board
> using an adaptor. If it is needed, Nicolas 6502 board can provide a
> solution.

Interfacing to the 8x50 FDC side isn't that easy with my board. I once did 
this, and had to do quite some rewiring to get extra lines on the GAL for 
decoding memory appropriately.

I don't remember exactly what I did, and I lost the source files for the 
GAL I used for this project. But I still have the finished board. It seems 
A12 and A11 are intercepted by the GAL, and decoding is extended to A10 and 
A7 and A6. I think I did this because the 6530 memory decoding is very 
weird, and I have to signal a certain memory hole to the 8x50 circuit so it 
will not activate the 6530 everywhere ... The design is based on the 6504 
after all with only 8kB memory space, so there are mirrors all over the place.

Adding IDE support to the 8x50 design might be easier than it seems. The 
DOS2.7 is very flexible with disk layout, and there is DOS3.0 for the CBM 
HD 9060 and 9090, and the hardware is quite similar to the 8x50, only there 
is a SASI Bus instead of the disk interface of the 8x50. So "only" the FDC 
code needs to be replaced, and the DOS2.7 or 3.0 can stay completely unchanged.

For who is interested I still have about 20 6502 expansion boards V1.1 here 
in stock, and I will make more when they are sold. There is a constant need 
for them it seems.


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