On 06-24-97 ROBERT OSBORNE wrote to DAN BRIDGES... 
 
 RO> Is the Rockwell chipset that you refer to here, a ROM or EPROM 
 RO> that is used to configure the modem or contains a program that 
 RO> runs a CPU  the modem to accomplish the compression and error 
 RO> correction of the data stream? Explain a little more about 
 RO> what it is used for and can they be up graded like BIOS? 
 
The chip set referred here is similar to the chip sets that are 
commonly found on the motherboards.  They are hard soldered on VLSI 
chips that contain, among other things, a built in CPU, PROM, and a 
host of supplimental parts.  The newest chip sets has an EEPROM 
(electrically erasable programable read only memory) built into it 
so that they may indeed "download" new software into it to handle 
new protocols.  This is something new and you will find it on the 
modems that are marked "upgradable to X2" or "upgradable to 56k". 
The older ones aren't upgradable.  There are no socketed parts, like 
ROMS, so there is no way to do the upgrade. 
 
 RO> Dan the communication program you are referring to here is a 
 RO> program like "Pro Comm or Telix" right?  I was not aware that 
 RO> you could do that. What are you doing here?  Does the setting 
 RO> that you make in the setup of the com program then control the 
 RO> speed of the I/O data stream being sent or received from the 
 RO> CPU/memory to the input/output register of the modem for 
 RO> internal or parallel port I/O for an External? 
 
I can't speak for Dan, however, I am using Telemate v4.21.  It has 
all the features that he mentioned.  He was referring to "port 
locking" and what that does is to prevent the software from setting 
the UART (on the motherboard if external, or on the FAX/Modem card 
if internal) to the same speed as the transmit/receive data speed of 
the modem.  It is usually set from 2 to 4 times faster.  Here is the 
why.  The faster modems, lets take a 28.8K modem for our example can 
compress the data being sent.  So lets take a chunk of data - oh -
lets make it 1K worth.  The modem, under ideal conditions, can and 
will compress it up to four times.  So our now 1K worth is now to 
256 bytes which is sent down the "tube".  Our receiving end will 
expand that back to the 1K, but if our port is set to the same speed 
as the transmit/receive speed, we can only receive the 256 and we 
wind up with a data overrun and lost data.  By locking at the top 
speed, we now get our 1K and no data loss.  We also get the 
equivalent transmit/receive speeds of 115,200 bps because of the 
data compression. 
 
Now I gave you an extreme example, but it is not uncommon to connect 
at 24,000 bps (not even the full 28,800 bps allowed) and get better 
than 4000 cps transmit rates with straight text files.  That is the 
equivalent of 32,000 bps. 
 
I forgot to mention with the port locking feature, that is one of 
the things that Terminate, Telemate, RIPTerm v1.58, Telix, Pro Com, 
and a host of other modem or FAX/Modem software will allow the user 
to set. 
 
 RO> Is it true that all machines 286AT, 386, 486 and Pentiums all 
 RO> have I/Os operating at 8 to 10 MHZ even thought the processors 
 RO> can operate at 100mherz or above internal and with memory? 
 RO> This is to keep a common exchange rate for all the external 
 RO> hardware on the market right? Since I am currently operating a 
 RO> 286AT @ 8 MHZ and a 386DX @ 33 MHZ I should be able to operate 
 RO> any of the new or old modems with both machines right?  I ask 
 RO> this because I often see ads for something like a Internal 
 RO> 28.8 KPS Data/Fax Modem that has V.34 including fax/data 
 RO> software and requiring a minimum system of : 486dx/33 
 RO> processor, open 8-hint ISA slot, Windows 3.1 (MS DOS 6.2) and 
 RO> 4 MB of ram, 5 MB H Dsk space. Am I correct in saying that the 
 RO> reason they specify the 486/33 and 4MB of ram plus 33 MHZ 
 RO> speed is to be able to run the software that they provide?  In 
 RO> other words they need these requirements to run under Windows 
 RO> with out slowing the system down so much that it can't handle 
 RO> the modem traffic and the program overhead?  If I were to just 
 RO> run the modem with dos 6.2 and the com program Telix on the 
 RO> 286 it would still work fine right? 
 
Ok, lets see now...  The I/O speeds are indeed at the 8 MHz level. 
That is primarily because that is about all that the traces on the 
mother board can handle without going to some very expensive and 
exotic methods of getting data from point a to point b on the 
physical mother board. 
 
The processor can handle a lot more.  The way that they typically 
handle that is through the cache memory.  Load the program and data 
into the cache and turn handle.  Very fast indeed. 
 
No you will not be able to use the high speed (14,400 bps or 
faster modem) with a 286.  You may be able to send at that speed, 
but you won't be able to receive.  The CPU will simply be 
overwhelmed by the data being thrown at it.  In fact, it becomes 
real iffy at 9,600 bps.  Experience has shown that a 286 will handle 
4,800 bps without trouble, but 9,600 bps and it is not all that 
stable. 
 
Actually, it has to do with the amount of data and the program 
overhead (not Windows).  With Windows software installed, the 
performance goes down even more.  All my examples given above were 
with DOS software and a system with minimum TSRs running. 
 
Remember what I said a couple of paragraphs above about a 286 
machine.  It simply doesn't have the ability to handle the through 
put that is required by a 28,800 bps modem.  You may connect at 
those respectable speeds, but then consistently get garbage.  It 
isn't the modem's fault, it is the processor simply can't keep up. 
And remember that I am talking DOS with a minimum number of TSRs 
(like no TSRs at all). 
 
I hope that this helps. 
 
Ed 
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