Fargo Heap Resizer
(C) 2005 Frantisek Dufka
HISTORY
version 0.14, 2005-10-9
- initial release, works for T and T2
version 0.15, 2005-10-28
- suport for Zire71 (1MB original, 1.96MB extended)
- can be enabled automatically on soft reset
- size on start/end labels is computed from real values
- scrollbar addded
- text field is now editable to allow clipboard operations on OS >5.4 devices.
DOWNLOAD
http://fanoush.webpark.cz/palm/fhr.zip
FEATURES
This program enlarges dynamic heap on Tungsten T and T2 devices from 800KB up to 1.8 MB and since 0.15 also on Zire71 from 1MB to 1.96MB. Memory for new heap is taken from storage memory. Unlike with other heap extending solutions this should be safe and transparent for all applications. Original storage memory protection is untouched and only memory used for new heap is made writable. Also no OS function is patched. In theory this is bullet-proof.
LIMITS
- So far works only on T|T, T2 and Zire71
- Not unlimited at all, 1.8MB is maximum for T and T2, 1.96MB for Zire71. This is of course not enough for running Doom but enough to play music on background while doing something useful or for playing some game that need a bit more heap memory than available (Legacy) or to see bigger pages in your web browser.
- As the heap is resized on the fly and already allocated and locked memory cannot be moved, new space is added in one or two separate memory chunks. This means that the free space is not continuous. Typically after program is run on T or T2 you end with 3 free blocks - 800kb,600kb and 200kb. This may cause some programs that need big chunks of continuous memory (e.g. one 1MB block) to fail even if there is enough free memory. You can use included ShowMemDA to see free space and largest continuous block.
USAGE
Execute the program as soon as possible after soft reset. Check at least one checkbox and press 'Resize heap now' button. You can use 'System info' for more details before or after resizing operation. Change is permanent until next soft reset. After performing soft reset original memory layout is automatically restored and allocated storage memory is freed by operating system (unless it is enabled automatically on each reset).
If it works fine, you can set it to extend heap automatically on each reset. If you have problems later, use no-notify reset (hold page up and reset your device) to prevent it from starting.
Included ShowMemDA is my Desk Accessory to show free memory and largest free block. Use DA launcher and choose Memory Info to get current memory information.
PRICE
This program is free for personal use. I wrote it to solve my problem with Legacy game by Redshift and just shared it for other users. However, it took me some time and required pretty advanced skills. If it works for you and brings new life to your device, you can send me a donation. $5 is a good choice like anything below or above this :) I will use it to buy shareware programs for my Palm . You can use https://www.moneybookers.com to send money to my mail. Unfortunately PayPal treat some countries differently so I cannot accept money via PayPal. If you really want to use PayPal, let me know.
DETAILS
Program works by mapping allocated block of storage memory above and below original dynamic heap space via MMU unit of the CPU and then tries to resize heap memory structures to accomodate new memory space. To describe it in simple words - the memory is cut from storage area and pasted around original dynamic heap.
There is only 800KB of unused address space below original heap beginning and 200KB after heap end on T and T2 so unless storage ram space is moved (which probably needs nontrivial ROM modification) 1.8MB is the maximum. Maybe I can get additional 200kb by moving the LCD framebuffer. On Zire71 there is space only below orginal heap.
Program is device specific but can be modified for other OS5 devices with low dynamic memory. Maximum size depends on memory layout of specific device.
No OS system function is patched and only specific allocated block of storage space is made writable in new memory mapping. In theory this means no data corruption is possible. New heap should be as safe as original unextended heap [*]. If device does not hang or reset itself on heap extension operation all the magic is done and it should just work. New memory is automatically available to all programs and operating system.
[*] On T2 this is not entirely true if heap is resized on heap end. There is SD/MMC buffer for reading from card directly after heap end. This buffer needs to be skipped and prevented from being used as free memory. Two solutions are used for this:
1. shortening last allocated block on heap end by 4 bytes to have space for chunk header that marks SD buffer as nonmovable allocated memory.
2. Last allocated block is extended to include SD buffer.
Both solutions are a bit dangerous. First can cause heap corruption and soft reset if those 4 bytes are really used and overwritten but advantage is that the SD buffer is never freed. Second solution can make the buffer free if last block is ever freed but leaves the last block data alone. In fact both solution seem to work fine as those 4 bytes seem to be not used and last block is never freed too. Currently method 1 is hardcoded as it causes immediate soft reset in case of problems which is better than corrupting data on your SD card silently by overwriting the SD buffer. If you care about extra safety you can uncheck heap end extension on T2. I have it enabled for months on my T2 without any ill effects but of course YMMV. On T|T there is no such buffer so it is safe and T|T owners get additional 4KB of space on heap end.
THANKS
Igor Nesterov for YAHM dev kit and tip about HALMemoryRegions
Greg Parker for Peal
mobile-stream.com for their unofficial SDK, I found most things before it was released but the SDK was still big help.
Michal Hrusecky for countless tests and resets on his T|T
TODO
- fix linked master pointer tables in original dynamic heap (trivial, not needed if FHR is executed relatively soon after soft reset)
CONTACT
See About dialog in menu.
Q&A
Q: Why Fargo?
A: Fargo 1 and 2 are internal codenames for T and T2, see http://homepage.mac.com/alvinmok/palm/codenames.html. As I added support for Zire71 in 0.15 the name is a bit misleading now. I should probably stop adding new devices or think about better name.
Q: Will you add support for my device?
A: Maybe, if it is easy. Do as it says, press 'system info' and send me output. Use stylus to select text and copy it to clipboard via command bar. If it crashes completely then it may be hard to add support for you device.
Q: What is the limit for my device?
A: Depends on memory layout. There needs to be unused virtual address space around original heap so there is space to grow the heap. If palm engineers wisely decided to put heap and other memory regions next to each other, nothing can be done.
Q: What is the difference between UDMH and FHR?
A: They are designed differently and they work differently. UDMH patches Memory Manager system calls to simulate dynamic heap in storage memory. Every allocation request for dynamic heap is rerouted to storage heap and a lot of magic is done to keep it working. Storage and dynamic heap data are mixed together which means that your storage data are not safe because they can be overwritten by bad software (This is just an educated guess, I haven't seen UDMH sources as it is paid). FHR really resizes original dynamic heap and leaves the rest to PalmOS, no system call is patched and in theory no additional data can be overwritten. The price for safety and stability is that FHR is limited by memory layout of the device and it is static - i.e dynamic heap cannot grow and shrink on demand like with UDMH. The only way to release memory taken by FHR is soft reset.
DISCLAIMER
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.