Cache Control is shareware! If you like it and use it, please send $10.00 to:
Jim Hamilton
2914 Aftonshire Way, #13102
Austin, TX 78748
For a copy of the latest version, guaranteed free of any illness, send either $12.50, or $10.00 plus a disk plus a stamped, self-addressed envelope. (it costs me about $2.50 to send a disk of my own--no profit here.)
Cache Control will allow you to set up the Instruction Cache on the MC68020, and both the Instruction and Data Caches on the MC68030. In particular, it allows you to turn the cache OFF, should you encounter a program which does not like having the cache on. Your selections remain valid until you change them (which could be over several startup/shutdown cycles).
To install Cache Control, simply drag it to your System Folder, and open the Control Panel desk accessory. Click on the check boxes for the caches, and you've done it!
In addition, Cache Control makes some patches to the system to do two things: First, it finds out what processor is running the Mac, instead of taking the system's word for it; this is useful if you have an accelerator card with a different processor from the one your Mac comes with. For instance, my Macintosh SE has a 68030 (and a 68000, but that mostly sleeps). CacheControl lets the system and applications know that it's there.
The second patch fixes a small but annoying bug in Microsoft Excel 1.5 (Bill Gates strikes again!). Excel was one of the first programs to send instructions directly to the 68881 floating-point coprocessor in the Mac II. To see if it can do this on a particular machine, it asks the system if an FPCP is installed, but ONLY IF THE MAIN PROCESSOR IS A 68020 (it should really ask if the processor is a 68020 or later). With the “Patch Excel” option checked, the SysEnvirons trap (which applications call to determine the features of the machine) will check to see if the application’s “signature” is ‘XCEL’ (for MS Excel). If so, and if the processor is a 68030 or later, it tells the program that it’s a 68020. This may seem like a non-kosher thing to do, but it works, and it doesn’t seem to affect any other programs.
Version 1.2 adds an option to check processor performance empirically. This is done by testing how many times a loop can be executed in a given amount of real time. The Macintosh operating system keeps a variable called “TimeDBRA” which describes how many times the 68000 family’s DBcc instruction can execute in one millisecond. This value is then used to calculate timing loops for a number of applications, such as network access and sound generation. For technical minded people, this is done by executing the following code:
MOVE.W #4,CCR
LOOP: DBNE D1,LOOP
Moving 4 into the condition code register sets the Z flag, so that the DBNE instruction will loop. A Time Manager task clears this flag after 16 milliseconds, and the loop is exited. The loop counter is checked to see how many times the loop executed, and this value is divided by 16 to obtain the calculated TimeDBRA.
Cache Control will work on any Macintosh computer with an MC68020 or MC68030 processor. To date, these include the Macintosh II, Macintosh IIx, Macintosh IIcx, Macintosh SE/30, and Macs with most accelerator cards. On other machines, it will simply refuse to run; i.e. it will not show up in the Control Panel.
LEGAL STUFF:
No warranty, expressed or implied, is granted for the use of this software. Any liability arising out of its use will be limited to shareware fees paid by the user.
Cache Control may be freely distributed, as long as no charge is made for the distribution. This means that it may be placed on bulletin boards which do not charge for specific downloads (a membership fee for the entire bulletin board is OK), on national services such as CompuServe, GEnie, Delphi, etc. Cache Control may NOT be sold or included for sale on the so-called “public domain” disks sold by EduComp, BudgetBytes, and others without the author’s express written permission. I am not unreasonable; if you want to include Cache Control on such a disk, let me know and we’ll try to work something out.
REVISION HISTORY
Version 1.0
Initial release.
Version 1.1
Add extra check for processor type and Microsoft Excel patch.
Version 1.1.1
Fixes a bug which showed only on 68000 or 68010 systems.
Version 1.2
Added option to check processor performance empirically, and modify TimeDBRA.
Seemingly, But Not Really, Off The Subject Dept.:
I would like to publicly thank the hundred or so people who have paid shareware fees for some of my other products, especially the Control Panel document ApFont. Your support has made this product possible.
