Re: RAM cards for IIe

["Bill Garber" <willy46pa@comcast DOT net>]

"David Wilson" <david@uow.edu.au> wrote in message
news:40fdee3a$1@news.uow.edu.au...
: "Paul R. Santa-Maria" <paulrsm@buckeye-express.com> writes:
: >Okay, Bill, now that you have the 4MB IIgs
: >RAM card done, how about a Slinky clone
: >that holds 64MB (four 16MB SIMMs)?
:
: >I think the Slinky uses three bytes for
: >addressing, so 16MB (four 4MB SIMMs or
: >one 16MB SIMM) might be the limit for
: >compatibility.
:
: >Even 4MB (four 1MB SIMMs) would
: >still be nice in an Apple IIe.
:
: There is no reason to make it strictly Slinky compatible
: as Apple always recommended that you access it through the
: Smartport firmware. That said, the card would be much more
: expensive to manufacture than the IIgs card.
:
: 1) Needs 8 bit bi-directional buffer on data bus
: to handle load of 6 other cards on the slot data
: bus. Minor cost.
: 2) Needs a 4KB EPROM and decoding logic to hold
: Smartport/ProDOS block driver code. Significant
: cost.
: 3) Needs logic to refresh all the RAM. This is
: the killer. The IIgs memory slot is designed to
: have DRAM plugged into it so arranges to refresh
: it.
: The Apple II bus does not (hence the ribbon cable
: to the motherboard on the original 16KB language
: card). Major cost.

Explain the "Pocket Rocket" which does not have a
cable to the motherboard. It also has fewer ICs
onboard. Well, that's partially self-explanatory.
The ram used holds more memory.

: The 8-bit Smartport allows 2**24 blocks of 512
: bytes using READBLOCK and WRITEBLOCK (8GB !!!)
: while the READ/WRITE commands only allow access
: to 2**24 bytes limiting it to 16MB which would
: work with a slinky compatible design.

That is very interesting.

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa @ comcast DOT net
Change DOT to a dot to contact me



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