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Re: What do I do next?
- Subject: Re: What do I do next?
- From: david@uow.edu.au (David Wilson)
- Date: 15 Feb 2002 15:14:02 +1100
- Newsgroups: comp.sys.apple2
- Organization: University of Wollongong
- References: <D0748.1874$mU4.97659@bgtnsc06-news.ops.worldnet.att.net> <zk748.144$_F4.92538@news0.telusplanet.net> <0eo48.2650$S67.154202@bgtnsc05-news.ops.worldnet.att.net> <Pvp48.3995$M3.596295@news1.telusplanet.net> <BMq48.2770$Ab1.169192@bgtnsc04-news.ops.worldnet.att.net> <Bqr48.4716$M3.671977@news1.telusplanet.net> <a453h9$6vv$1@venus.itns.co.za> <a45k9r$16ki$2@nserve1.acs.ucalgary.ca> <1f7fsrr.kmo88l1lwsr7vN%dempson@actrix.gen.nz> <a47d30$1a0k$2@nserve1.acs.ucalgary.ca> <1f7gti9.ag8ovn17avszoN%dempso
- Xref: archiver1.google.com comp.sys.apple2:17542
dempson@actrix.gen.nz (David Empson) writes:
>Yes. The "Apple II Memory Expansion Card" works on all Apple II models
>with slots. It was typically supplied with 256 KB of RAM and is
>expandable up to 1 MB, using 256Kx1 RAM chips in sets of eight.
>I'm somewhat rusty on the other user-level details. I'm slightly more
>familiar with AE's RamFactor, which works on the same principle but has
>additional functionality. In particular, I forget whether Apple's card
>supports DOS 3.3.
It does - IN#n will patch DOS to allow the card to be used as a 256KB or
400KB disk (if I recall this correctly).
>At the hardware level, the card uses four locations in the I/O space
>allocated to the slot to implement a three-byte address register and
>one-byte data register. Applications are not supposed to use this
>interface directly - the SmartPort driver on the card is the recommended
>method for doing data transfers between the card and main memory.
Yes. Looking at the source code (either disassembled or as listed in the
Technical Manual for the card) reveals that the Smartport firmware also
can read/write directly into Aux RAM.
>The Apple IIc memory expansion card (supported by the revision 3 and 4
>firmware, and the last motherboard revision of the IIc) works on the
>same principles, and is 100% compatible at the software level.
The //c card is almost the same as the ][ card apart from the connector
and the lack of onboard firmware (the //c has the firmware on the motherboard).
>The Apple IIc+ memory expansion slot also works on the same basis, but I
>gather that the IIc memory expansion card doesn't work in the IIc+,
>possibly due to timing issues or some other hardware problem.
The code is highly optimised and I suspect that the ASIC cannot handle
the data throughput of an accellerated machine (my Transwarp //e had problems
with it as well) - the cache could improve things to the point that back to
back writes to (or reads from) the card could occur without giving it time
to increment its address registers (or perhaps perform refresh).
One day I will try pessimizing the code and see if it works with my Transwarp.
--
David Wilson School of IT & CS, Uni of Wollongong, Australia