[rescue] Dataram 64mb sbus ram expansion

[Ethan Hawke]

On 2/14/25 15:42, foo bar via rescue wrote:

> On Thu, Feb 13, 2025 at 10:46 PM Henry Bent via rescue
> <rescue at sunhelp.org> wrote:
>> On Thu, 13 Feb 2025 at 22:17, William Barnett-Lewis via rescue <rescue at sunhelp.org> wrote:
>>>
>>> BUT the big surprise that I had forgotten I had was a Dataram 64mb
>>> sbus memory expansion (with the all important ribbon cable) from a
>>> long gone IPX.
>>
>> I had never seen one of these before.  Apparently they're only for the SS2 and IPX, and require additional power from a special motherboard connector.
>>
>> What would happen if you put it in a different machine, and were able to externally supply the correct power?  Could this theoretically work in an SS1, or an IPC?
> This specific card won't work but the general idea will. On sun4c sbus
> is the system bus so the CPU, MMU and memory controller all sit on
> sbus. So this card is literally just the same memory controller that's
> on the motherboard plus some RAM. The SS1/1+/IPC use an early version
> of the memory controller so you'd have to use one of those to make
> this kind of card for them. Which is exactly what the sun4e memory
> expansion board does as you can see here.
>
> https://www.ebay.com/itm/305846748548
Indeed, although the special cable is needed to expose the extra 
addressing line to let the memory sit in the cache-able memory space and 
not the IO (SBus) space.

In addition the connector is on the SS1/SS1+/IPC, but it has a different 
pinout.

More details are available in the FORCE-2CE manual on bitsavers (or 
archive.org), including a schematic.

  - Ethan