RAM Disk and Memory Extension for Macs with 8 or More Megabytes of RAM
Maxima 2.0 is the unique RAM enhancement utility which creates a protected, non-volatile RAM Disk and extends 24 bit addressing capacity. It is intended for use on Macintosh systems with 8 or more megabytes of physical RAM and is fully compatible with System 6 and System 7.
The RAM Disk converts SIMM or NuBus RAM into an ultra-fast storage device which appears on the Desktop and can be used like an ordinary hard drive. The addressing enhancement allows up to 14 megabytes of physical RAM to be accessed for application memory in System 6 or System 7 using 24 bit addressing.
System 6
One of the main limitations of System 6 is that it can only recognise eight megabytes of application memory. Under System 6, when more than 8 megabytes of RAM is installed, it is ignored by the system. Using Maxima, up to 14 megabytes of RAM can be recognised, and any additional RAM can be utilised as a protected, nonvolatile RAM Disk. Maxima offers System 6 users with 4 megabyte SIMMs, large composite SIMMs or NuBus RAM cards the ability to use this memory to maximum advantage.
System 7
Under System 7, large amounts of memory can be addressed using the 32 bit addressing capability on most Macintosh systems. However, many applications and Startup documents (INITs) are incompatible with 32 bit addressing. When 32 bit addressing is turned off (or is not available) 24 bit addressing must be used. These applications can still be assigned large amounts of RAM by using Maxima. In System 7, Maxima provides the same 14 megabyte memory extension and RAM Disk as in System 6. Since Maxima extends memory addressing without resorting to 32 bit mode it is compatible with essentially all applications.
Maxima 2.0 offers additional capabilities whenever 32 bit addressing can be used. In this mode Maxima creates a RAM Disk which is configured independently from the 24 bit RAM Disk.
RAM Disk
In both System 6 and System 7, Maxima creates RAM Disk with the amount of RAM specified by the user. The RAM Disk can be used under both 24 and 32 bit addressing modes.
The RAM Disk appears on the Desktop like a hard drive, and documents can be added, accessed, modified or removed in the same manner as on a hard drive. When the RAM Disk contains a System and a Finder, it is automatically used as the Startup Volume. This significantly reduces boot time and speeds up many routine operations. The RAM Disk can also be used to store large documents (like databases or graphic images) which can accelerate the running of memory-intensive applications.
The Maxima RAM Disk includes an innovative non-volatility feature that substantially enhances its usefulness. Historically, RAM Disks have been volatile - a system crash, power down, or Restart would erase them. Because of this, RAM Disks have traditionally been used as ultrafast scratchpads. In contrast, the Maxima RAM Disk survives restarts, shutdowns and system crashes and can therefore be used more like an ultrafast hard drive.
The non-volatility is created by maintaining an updated copy of the RAM Disk on a hard drive. If the Save Files at shutdown option is selected, any information which has changed on the RAM Disk since the last Shutdown is automatically preserved on the hard disk. The Copy Files at startup option then takes this saved RAM Disk image from the hard drive and loads it back into the RAM Disk at boot time. In addition, unless the power is interrupted, the RAM Disk contents are preserved through Restarts and system crashes. In fact, Maxima's RAM Disk works just like any other hard drive, except hundreds of times faster.
You can also choose to protect the RAM Disk so that errant applications are prevented from altering its contents. With Protect RAM Disk turned on, only the Maxima RAM Disk drivers can change the RAM Disk contents.
Memory Extension
Maxima extends 24 bit mode addressing from the usual limit of 8 megabytes to as much as 14 megabytes. Since it does this without resorting to 32 bit addressing it is compatible with essentially all applications, even those which are not 32 bit clean.
Maxima enables Macintosh systems to go beyond the 8 megabyte barrier using actual RAM. With Maxima, the upper limit is 14 megabytes unless multiple NuBus or display cards are installed, which reduces this maximum. Macintosh systems with more than one NuBus car installed can access 1 megabyte less for each additional card. The amount of extended memory is easily adjustable using Maxima's cdev.
Users of both System 6 and 7 can take advantage of the enhanced 24 bit addressing mode offered by Maxima. System 6 always operates in 24 bit mode (unless the Connectix product, Optima, has been installed). System 7 users who have systems that support 32 bit mode will elect 24 bit addressing to run applications and Extensions which are incompatible with the new 32 bit mode.
System Requirements
Maxima will work on any Macintosh which has a Memory Management Unit. This is standard on every 68030 based Macintosh (IIfx, IIsi, IIci, IIx, IIcx, and SE/30). It can be retrofitted to any original Macintosh II by installing a memory co-processor, the MC73 PMMU Paged Memory Management Unit.
