Re: LZ: I think I have a definite plan for memory... I think...
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Re: LZ: I think I have a definite plan for memory... I think...
On Sat, 21 Sep 1996 16:43:52 -0700 (PDT), you wrote:
>Steve Wrobleski wrote:
>
>Microwire will only work with Mel Tsai's expander, which looks =
promising,
>but is a large amount of trouble to go to. There is also the matter of
>addressing; you can only transfer so fast with only 2 wires, especially
>considering that the processor is only 6Mhz, 13 if turboed. You can =
only
>transfer as fast as the processor can translate and recieve from the =
port;
>Let us remember that the original 8088 ( 4.77 Mhz, not too much slower =
than
>the TI ) couldn't do much more than 2400 on a modem, 4800 or 9600 if you
>were lucky; and it had the luxury of a 28-pin parallel / 9-pin serial =
cable
>to send data through. With only two wires, it will still be rather =
slow.
A 4.77 Mhz 8088 is actually more powerful than a 6 Mhz Z80, but that
doesn't matter. Remember, the original IBM's had a lot of overhead to
deal with. They had to coordinate interrupts, DMA, video, DRAM
refresh, disk access, error correction and a host of other things.
Those original modems didn't have very good error correction, and they
had no compression. They were pretty much "dumb", and it took some
work to interface a "fast" modem such as a 2400 baud to interface to
it. The TI-85 has *no* overhead (accept for screen refresh), and
therefore the transferr rate will be greatly increased.
>Combined with the time it will take to pick one page out of 500KB / 1MB =
and
>that the size of pages will most likely require writing entire blocks of
>memory that might not be used at one time, unless Mel's software for his
>expander supports fragmentation and has one hell of an interface I doubt=
too
>many casual users will do it.=20
>
The file fragmentation won't be as complicated as you think... It
will be pretty fast, probably much faster than regular calculator to
calculator linking. I'm estimating anywhere from 1 to 5 kilobytes per
second. Searching through the entire 512k or 1024k won't take more
than two or three seconds!! Of course, you can't read every byte in
that time span, but you can get all the file header information. You
can read or write bytes to the expander pretty much randomly, but the
problem arises when you want to erase something. This really won't
mattter, however, as it will all be handled in the background.
The software interface won't be more than 2 to 3 k in size, and for
now it will be used just as a file storage/retrieval system. I'm
thinking of making two versions, one with a whole bunch of "bells and
whistles" and another "lite" version with functionality but 50 - 75%
smaller. It will be a while before any other program physically
accesses the expander, although I'll release all the vital
send/receive routines soon.
-Mel
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