Re: ROM 1 vs. ROM 3

[Aleon@aleon.freeserve.co.uk]

In article <1dmvd6s.1mxebme1oyvgigN@dempson.actrix.gen.nz> ,
dempson@actrix.gen.nz (David Empson) wrote:

>[Please note that I've crossposted to comp.sys.apple2 and set followups
>there.  This discussion is nothing to do with Apple II user groups.]
>
>Charles J. Sarchet <csarchet@ix.netcom.com> wrote:
>
>> The best reason to upgrade to a ROM 3 is if you have an accelerator board
>> like the ZipGS or the Transwarp installed, and you are planning to
operate
>> it at faster than 8 Mhz.
>> 
>> As I remember, this is the magic number for the ROM 1.  If you accelerate
a
>> ROM 1 much above that, then you will start to experience multiple system
>> crashes.  Why?  well the story I used to get was that the ROM 1 was a
single
>> layer board and the ROM 3 was a multiple layer board and so on the ROM 3
the
>> circuitry could be spread out across multiple layers.  Another story goes
>> that the ROM 3 has fewer components on the board. Buzzzz... incorrect. 
In
>> reality, they are both single layer boards printed on both sides, and the
>> ROM 3 actually has more components (although not many more) then the ROM
1,
>> however the etching on the ROM 3 is a few microns smaller then that on
the
>> ROM 1 and the spacing between the etching is a few microns wider and
>> therefore can handle the faster clock cycles.
>
>Buzzzz.  Lots of mistakes in there.
>
>1. I'm not aware of significant problems with crashes when using
>accelerators above 8 MHz on the 256KB motherboard, though I've never
>used one faster than that.  Anyone have any practical experience in this
>area?
>
>2. Both the original and 1MB (ROM 3) IIgs motherboards use four layers.
>
>3. The number of components on the two motherboards are pretty similar.
>The 1MB motherboard has two ROM chips and eight fast RAM chips compared
>to one and four respecitively for the 256KB motherboard.  The 1MB
>motherboard is missing several connectors for IIe compatibility, but
>there aren't many components associated with them.
>
>4. The 1MB motherboard is generally designed better than the 256KB
>motherboard.  It has less induced noise (particularly in the sound
>circuitry) and consumes less power than the 256KB motherboard, so the
>machine tends to run a little cooler.  This may account for better
>accelerator operation.
>
>5. Using an accelerator does _not_ affect the speed of data transferred
>over the motherboard.  The accelerator does all high-speed operations
>internally, using caching to achieve the speedup.  Access to the
>motherboard is controlled by the clocks on the motherboard, which are
>exactly the same whether you have an accelerator or not.
>
>> Some other differences that are worth noting:
>>
>> - the battery on the ROM 1 is soldered to the motherboard, while the ROM
3
>> has a battery holder.
>> 
>> - the ROM 1 can be inserted into an Apple //e case because it has points
on
>> the board to which the appropriate connectors can be soldered, while
these
>> have been removed from the ROM 3.  The original upgrade board already had
>> the connections soldered in place.
>> 
>> - the ROM 3 has 1M of Fast Ram instead of the 256K on the ROM 1.
>
>It is also worth noting that with a standard 4 MB memory expansion card,
>you get 5 MB of DMA-compatible fast RAM in a ROM 3, compared to 4.125 MB
>for a ROM 1.  Both machines can access a maximum of 8 MB of fast RAM,
>but there may be compatibility problems.
>
>> - the ROM 3 has a newer and bigger toolbox (although I think most of this
>> became obsolete with GS/OS 6.01).
>
>Some of the ROM-based desktop toolsets in the ROM 3 are replaced in
>entirety if you run System 6.0 or 6.0.1, but there are still a fair
>number being used from ROM (with RAM-based patches for a few calls).
>
>In particular, QuickDraw II has very few changes between System 5.0 and
>6.0.1, and runs almost entirely from ROM in the ROM 3.  This produces a
>noticeable speed improvement for desktop applications, since ROM
>accesses are not slowed down by fast RAM refreshing.
>
>
>Some other differences that I can think of:
>
>- the ROM 3 has several improvements to the system monitor firmware,
>allowing operations like dumping memory over bank boundaries,
>disassembly automatically tracks register size changes, simple step and
>trace facility built in, etc.
>
>- the ROM 3 (actually the motherboard) supports hardware shadowing of
>text page 2, which means that "Alternate Display Mode" no longer causes
>a significant slowdown if enabled.
>
>- Sound circuitry has significantly less induced noise from the
>motherboard.
>
>- ADB microcontroller in the ROM 3 has built-in support for "sticky
>keys" and "keyboard mouse"; these are provided by the Easy Access INIT
>for ROM 1, but the software-based version has significant compatibility
>problems.
>
>- ADB microcontroller in the ROM 3 automatically updates the Caps Lock
>LED on an extended keyboard.  :-)
>
>- Slot 4 can be set to "Your Card" without losing access to the mouse in
>GS/OS applications (you still lose it for ProDOS-8 applications).
>
>- AppleTalk firmware improvements, particularly in how the slot mapping
>is handled.
>
>- RAM disk can be resized without turning the machine off or running a
>self-test.  The RAM disk loses the ability to set separate minimum and
>maximum sizes, since this feature causes problems.
>
>- Apple 3.5 Drive firmware is noticeably faster (affects ProDOS-8 only).
>
>- One particular signal is provided on slots 1 through 6 instead of just
>slot 3, allowing the Video Overlay Card and/or Second Sight to be used
>in any of these slots without modifying the motherboard.
>
>- A jumper provides a mechaism for locking out access to the text-based
>control panel (intended for classroom situations).
>
>> mrl wrote in message <797eko$ffb$1@remarQ.com>...
>> >Question: What is the difference between a ROM 1 Apple //gs and a ROM 3
>> >Apple //gs?  I've got a ROM 1 machine, and was wondering if there's any
way
>> >to upgrade it to a ROM 3 machine, or if such an upgrade is even
necessary
>> >or practical...
>
>The only way to "upgrade" to a ROM 3 is to replace the entire
>motherboard.
>
>Apart from the above details, there are no significant improvements,
>e.g. CPU speed.
>
>> >I'm wanting to set it up in the computer room alongside my mac and have
a
>> >machine that I can use to access the internet and pick up email and read
>> >news while my wife does amazing multimedia stuff on the mac.
>
>-- 
>David Empson
>dempson@actrix.gen.nz
>Snail mail: P.O. Box 27-103, Wellington, New Zealand


errrrr I don't think I know the answer to that