Speed of BIS memory verses SD

STE699 · 05-23-05, 09:43 AM

Hello, i keep reading that BIS (internal memory) is the slowest form of memory. However on putting the high bitrate file (Betaplayer site) in the BIS and benchmarking it with Betaplayer it accually reports 183% 3.0Mbs where as SD card shows 2.9Mb/sec. What gives?

Ward · 05-23-05, 09:51 AM

High read speed - but very poor write speed is whats reported.

Also, sequential access seems fast, but direct access isn't. i.e., reading a large file in sequential chunks - a video - is fast. Reading many parts of a file in no sequential order - a dictionary or program - seems slow.

Calligraper really doesn't like being installed in the BIS - but if you move the recognition engine and the dictionaries to a high speed SD or RAM, recognition reliability increases. The culprit in this case is that Calligrapher will always give its best guess in a configurable amount of time. With the engine stored on the BIS, more of that time is spent accessing rather than processing.

For most programs, segments are loaded into RAM at first execution so speed isn't affected. For those apps which access large amounts of data regularly, the BIS is a bottleneck.

Here are some examples as far as my experience goes:

Games - Alright - most load and buffer in the RAM. Loading is sequential so fast enough to be unnoticeable.

Reference - Poor. This includes dictionaries, maps, sophisicated programs, etc. Its due to the way data is arranged - often using binary trees or similar which precludes sequential access.

Applications - Alright - most are sensibly segmented by their compilers so load a start section, middle section and end section appropriately and entirely into RAM.

Adrian Knack · 05-23-05, 09:57 AM

That is right... fast read but slow write.

Reading non-sequential files is slow because there is no FAT, hence it seaches sector by sector - read my SD Card formatting tutorial in the tutorials section, the same applies to your BIS except you can't format it with a FAT.

BIS should really only be used for files that don't change often ie. documents, videos, some programs.

Edit: BTW nice banner Ward. Guess you are a 3D graphic artist.

Cheers

STE699 · 05-23-05, 09:59 AM

ok, thanks :)

Ward · 05-23-05, 10:06 AM

Not an artist - just talented with Photoshop.

;)

K7a · 05-23-05, 11:38 AM

Do high speed SD cards such as the Ultra III from Sandisk have a increased write speed proportionate to their faster read speed?

Adrian Knack · 05-24-05, 01:13 AM

The answer is yes... but only in a card reader or a camera that will support the higher speed. The Axim (and all other PDAs at the moment) will not read/write any faster with high speed cards.

Cheers

05-24-05, 01:56 AM

Originally Posted by Adrian Knack

The answer is yes... but only in a card reader or a camera that will support the higher speed. The Axim (and all other PDAs at the moment) will not read/write any faster with high speed cards.

Cheers

would you happen to know what rate it can handle? the SD and CF slot. I only own 1 sd card and ultra ii 1gb card and am considering to purchase a 4gb ultra ii cf. was wondering if it might be a worthwhile purchase.

Adrian Knack · 05-24-05, 02:02 AM

About 8.0x read and <1.0x write is what was benchmarked for SD and the CF is about the same. There was a big tet not so long ago run by Chiorguy.

If you have a card reader you will find the high speed useful because you will be able to copy your data much faster. If not and you will just have it in your PDA a normal one is fast enough. Ultimately it depends on price (if they about the same go high speed you can't lose)and what you want.

I got my 1GB SD-card for $155 Australian which at the time was cheaper than the standard SanDisk cards and I have had no problems. It is a "Silicon Power" brand if you are interested.

Cheers

K7a · 05-24-05, 11:59 AM

Is the limitation in the software or hardware? Does WM5 make any differences in this area?

Adrian Knack · 05-25-05, 01:26 AM

I am not sure. Probably hardware or somebody would have come out with a hack to improve it.

medevo · 05-25-05, 01:34 AM

Originally Posted by K7a

Is the limitation in the software or hardware? Does WM5 make any differences in this area?

Read the Section "Why is my memory slower on the PDA then on my Camera/Computer?" on
Memory Faq.

You may be able to increase write speeds of flash by altering the current reduction circuitry, but that is complex and has a very high chance of destroying your PDA.

DMA, and the speeds attached, is not coming to this generation of PDA, and do not hold your breath on the next.

Medevo