Re: //e DMA & //c question

[dempson@swell.actrix.gen.nz (David Empson)]

In article <1994Jan8.130327.12683@roxi.rz.fht-mannheim.de> chk@aix01.rz.fht-mannheim.de (Karpp Christian) writes:
> hi,
> does anybody know, if there are dma-capable accelerators for the //e
> available?  maybe in combination with dma-capable ram-cards?

No to both.  The ZIP and Rocket Chips are certainly not DMA
compatible.  The TransWarp has the potential (since it is connected to
the slots) but is not DMA compatible either.

It makes no difference whether the RAM cards are DMA compatible or
not.  The problem is that the accelerators do not recognise a DMA
access.  For the ZIP, this means that a DMA access to a location which
has already been cached will not update the cache.  The TransWarp
replaces the memory of the IIe with fast on-card RAM, and the DMA
access will not affect the contents of the fast RAM.

> and does anybody remember the difference between the "old" //c and
> the "new" ones?

Not counting the IIc+, there have been four versions of the IIc.  You
can identify which version of the IIc you have by getting into BASIC
and typing PRINT PEEK(64447).

The number reported will be one of:

255  Original IIc
0    "UniDisk" IIc
3    "Memory Expansion" IIc
4    "Revised Memory Expansion" IIc
5    IIc+

An original IIc can be upgraded to a "UniDisk" IIc by replacing the
ROM and making a couple of minor modifications to the motherboard.

There is another potential problem with the original IIc: it uses the
wrong clock speed for its serial ports, and the communication speed is
slightly out.  Whether this is a problem depends on the device you
have connected to the serial ports.  It is usually no problem for
printers, and for modems at 1200 bps or slower.  Some people have
encountered problems at 1200 bps or faster.

To fix this problem requires a motherboard exchange.  A newly
purchased "UniDisk" IIc already has the revised motherboard.

There are a few new features in the "UniDisk" IIc:

- Support for UniDisk 3.5 and other "SmartPort" devices (e.g. Chinook
made a IIc-compatible SmartPort hard drive).
- A mini-assembler, and step and trace commands in the monitor.
- More commands in the serial port firmware, improving compatibility
with the Super Serial Card.

One feature was removed: the ability to boot from slot 6, drive 2 by
using PR#7.

The "Memory Expansion" IIc has yet another motherboard, this time with
a memory expansion slot added.  There is additional software in the ROM
to support this.  The memory expansion slot allows you to connect an
Apple IIc Memory Expansion Card, which works like the RamFactor or
Apple II Memory Expansion Card, i.e. a standard slot memory card
("slinky") as opposed to a IIe auxiliary slot memory card ("bank
switched") like the RamWorks.

The fourth version is a ROM upgrade to fix bugs in the earlier versions.


The IIc+ is effectively a different computer.  It has a built-in 3.5"
drive instead of a 5.25" drive.  You can connect Apple 3.5, UniDisk
3.5 and 5.25" drives to the disk port.  It also has:

- An accelerated microprocessor (4 MHz; equivalent to a ZIP chip).
- Revised keyboard layout.
- Internal power supply (eliminating the "brick", but it means you
cannot run a IIc+ from a car's cigarette lighter).
- Internal modem connector (I don't think a modem was ever made to
work with this).
- Serial ports use Mini-Din-8 connectors (like the IIgs and Mac)
instead of DIN-5.
- No headphone jack.
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand