A600 8Mb fast expansion

[lordv]

Just curious... Do you know if adding a 020 would add too much complexity to your design? Anyway great job!

I'm afraid it would be totally new design...

[lordv]

skurk wrote:
Awesome!  I want one (provided that it doesn't disable my PCMCIA port)

Please say me somebody what address space is for PCMCIA on A600, then I'll give you clear answer.

[tokyoracer]

This is excellent, A great way to boost the cute little machine. I couldn't ever build such a thing though... :-(

[Matt_H]

@ lordv

From NDK3.1:Examples1/PCMCIA/PCMCIA.General

Because the A600/A1200 PCMCIA implementation is entirely memory mapped, the
maximum common memory address space is limited to four (4) megabytes.  The
upper half of our eight ( megabytes of 24-bit expansion space ($600000
through $9FFFFF) has been used for this purpose.  Another 128K of address
space ($A00000 through $A1FFFF) is used for attribute memory, and the next
128K bytes ($A20000 through $A3FFFF) is used for I/O address space.

This means that our 24-bit CPU systems can use common memory for Execute-In-
Place purposes (SYSTEM RAM expansion, and Execute-In-Place code).  The down
side is that our current implementation does not yet provide a paging register
so that addresses greater than 4MB cannot be generated.  While our system
software cannot currently support XIP and bank switching well, the extended
address space will be useful if we want to support large FLASH-ROM cards.  A
paging register is being considered for this purpose in the future.

The PCMCIA slot does have some limitations.  It is a 16 bit interface, and
most SRAM/PSRAM cards are 200-250ns requiring GAYLE provide wait-state
generation.  A specification for PCMCIA DMA was not finalized for the Release
2.0 specification.  We realize that some of you will prefer to use the common
memory space for 32 bit RAM expansion in the A1200, so a credit-card disable
register is provided in GAYLE.  Software modifications have been added to the
latest V39 release which automatically disables the PCMCIA interface when RAM
is present in card memory space (this does however mean that you lose use of
your PCMCIA slot).

[alexh]

lordv wrote:
Please say me somebody what address space is for PCMCIA on A600, then I'll give you clear answer.

0x600000 to 0x9FFFFF

[rkauer]

 Without another processor (<>68000) you cannot use more than 8Mb inside an A600 (68000 use a 24bit address space = 8Mb).

[alexh]

rkauer wrote:
68000 use a 24bit address space = 8Mb

24-bit = 16Mb ;-)

[da9000]

@lordv:

AWESOME!

Maybe you should talk to Individual Computers and join'em on their A600 accelerator project...

[yssing]

If you sell them I would buy one

[lordv]

0x600000 to 0x9FFFFF

So, there should be 2 versions - one autoconfiguring as 8mb with no pcmcia, other with only 4mb onboard =)

[countzero]

isn't it possible to put a jumper or something to altera chip so that it uses only $200000-$5FFFFF when jumpered ?

[lordv]

Currently no, because all pins of altera used up

But you can have two of them, replacing when needed =)

[alexh]

Could you add a config register?

[lordv]

alexh wrote:
Could you add a config register?

What do you mean? Currently autoconfig only used in a tricky way only telling system we are, but ignoring high byte address system assigns to us. I can latch address given by system, but correct decoding of it will cause extra arithmetics/whatsoever so that design won't fit into epm7032. 7064 would probably help, but what for? It is expected we are the only autoconfiguring device in A600 =)

[alexh]

I was wondering if you could add a register that when you write a particular value to it, it stops decoding addresses in the upper 4 Mbyte range.

You could then switch on/off the upper 4Mbytes in software.

[TjLaZer]

I have been looking for such a product!  You should make it so  it accepts a single 72pin SIMM!  That way the end user can install a 4MB or 8MB SIMM!  I would like to have a 4MB version, that way I can use my PCMCIA port!  If you consider selling a 4MB version let me know, I would buy atleast two!