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Old 15 February 2009, 01:11   #1
Iznougoud
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Maximum speed of the internal serial port?

Just out of curiousity; does anyone know any figures concerning the maximum speed/transfer rate of the A2000/A500 serial port?
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Old 15 February 2009, 01:20   #2
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Depends on processor speed. My A1200 with a '030/50MHz does 115,200kpbs, you'd get quite a bit less with a standard A500 or A2000.
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Old 15 February 2009, 01:24   #3
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Quote:
Originally Posted by Iznougoud View Post
Just out of curiousity; does anyone know any figures concerning the maximum speed/transfer rate of the A2000/A500 serial port?
Hi Iznougoud,

I only managed to get my A1200 working with Amiga Explorer at 19,200 Baud rate when I first bought it. That seemed pretty good back in those days.

When I used it again recently without changing the settings it seemed dead slow. I haven't looked again at whether it's possible to increase this transfer rate, because I can't believe I would have set it to that speed if it had been possible to increase it back then (my PC would have been good for 115,200 Baud rate).

So you may find that 19,200 is the fastest possible. But I could very well be wrong.

prowler

PS. A1200 was not accelerated in either case.
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Old 15 February 2009, 08:48   #4
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Use add44k or whatever to drop your screen depth, you'll be able to get a little bit more speed that way.
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Old 15 February 2009, 09:00   #5
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115200 with my a500/060 when using RTG screens.
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Old 15 February 2009, 09:17   #6
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Well, the reason for me asking is that I recently managed to get my A2000 online, using ICS via nullmodem. Having gotten used to a 100Mbit/s connection, obviously this was painfully slow (the transfer rate is set to 57600), and remembering some ancient info on the limitations of the serial port of the Amiga, I thought I'd check to see if there would be any point in cranking it up to 115200. Although I doubt the actual transfer rate will come anywhere near that.

As for AExplorer, I really don't think that's a good reference. I've had the same experience, 19200 as maximum. And even then I would get errors when transferring large files. I really see no use for that software, unless you don't have a LAN available. But maybe I'm wrong.

My A2000, by the way, isn't the fastest one around. But I do believe it can hold it's own with the Blizzard 2040-board, Picasso II and 128Mb FastMEM (I do love lots of RAM . I fail to see, however, how screen depth would affect the transfer rate of the serial port. Would anyone care to elaborate?

(As a note; for some reason AWeb won't work. IBrowse and AmIRC works just fine, so I must have missed some setting in AWeb. Any ideas about that?)
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Old 15 February 2009, 09:50   #7
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More planes = more dma load = less time available for your beloved serial port.

RTG will help, but you must configure it to not display a custom chip screen at all when you have an RTG screen visible.
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Old 15 February 2009, 12:03   #8
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Right. Hadn't thought of that. I have, however, configured Workbench to utilize Picasso for every screen possible in order to conserve ChipMEM, so hopefully that will be enough (the amount of available ChipMEM is never below 840Kb - out of 1Mb - regardless of the number of screens).
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Old 15 February 2009, 16:06   #9
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Use just two colours with the worst possible resolution and you will achieve higher serial transfers. But it will be a PITA to use.

Better use a dedicated serial port and RTG video.
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Old 16 February 2009, 11:48   #10
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Depends on processor speed. My A1200 with a '030/50MHz does 115,200kpbs, you'd get quite a bit less with a standard A500 or A2000.
I was wrong on this one, it's actually 57.6 I get on my A1200 '030.
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Old 16 February 2009, 19:44   #11
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With baudbandit.device I could get at least 14.4k reliable connection on a 19200 baud rate on a bog standard A1000 (which I think had a max listed ability of 38400 baud rate) with a colour depth of 2 bitplanes at 640x256. Serial.device on that config may have only allowed 9.6k connection. It was a long time ago, so the speeds may have been slightly quicker. So I would think a standard A1200 with an 020 should be a decent chance of beating that by a bit.

http://www.amiga.org/modules/newbb/v...=44147&forum=9

Similar question to yours, someone said they got 38400 on a 68000 with some errors.

Not sure if baudbandit.device works with null modem. Maybe also look for other serial.device replacements.
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Old 30 July 2013, 04:39   #12
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Amiga serial speed

I did a serial transfer on a number of occasions between an Amiga 4000/030 and a stock Amiga 2000. The transfer was at 57,600 bps. That's the fastest setting in the program I was using (Jr Comm).

In regards to the original chipset, the Amiga Hardware Reference Guide states that "With a cable of a reasonable length, the maximum reliable rate is on the order of 150,000-250,000 bits per second." (p. 255, Commodore-Amiga, Inc. 1991).

It goes on to mention that at speeds like that, interrupts are not possible and "The receiving end will need to be in a tight read loop."
 
Old 30 July 2013, 05:08   #13
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It goes on to mention that at speeds like that, interrupts are not possible and "The receiving end will need to be in a tight read loop."
Yep.

And many PCs of the same time period often had to resort to the same technique!

It's too bad the Amiga was first designed to be a dedicated game console with most DMA directed towards audio/video handling. If additional DMA had been set aside for I/O it would have made for an even more amazing PC. That might have happened had the designers gone directly for the personal computer market.

One thing I envy about the Atari ST is the spare DMA channel for hard disks.
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Old 30 July 2013, 10:24   #14
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dma load is not going to affect serial port speed unless you don't have fastram (which affects cpu speed)..

the serial port itself can go plenty fast, but as mentioned above, the problem is it interrupts the cpu for each byte transferred, which takes a *lot* of processing power.. That's why pc's switched to UARTs having FIFOs in the beginning of the nineties..

Last edited by hooverphonique; 30 July 2013 at 10:47.
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Old 30 July 2013, 10:36   #15
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dma load is not going to affect serial port speed unless you don't have fastram..

the serial port itself can go plenty fast, but as mentioned above, the problem is it interrupts the cpu for each byte transferred, which takes a *lot* of processing power.. That's why pc's switched to UARTs having FIFOs in the beginning of the nineties..
I wasn't clear.

I meant additional DMA channels for IO.

Serial port send/receive buffers in chipram with their own DMA channels would have been very nice.
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Old 30 July 2013, 10:46   #16
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Serial port send/receive buffers in chipram with their own DMA channels would have been very nice.
indeed...
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Old 30 July 2013, 10:55   #17
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Polling works at least up to ~600kbits/s, VBS (Video Backup System) uses SERPER value of $8003 when reading backup tape.
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Old 30 July 2013, 11:02   #18
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Hi Iznougoud,

I only managed to get my A1200 working with Amiga Explorer at 19,200 Baud rate when I first bought it. That seemed pretty good back in those days.

When I used it again recently without changing the settings it seemed dead slow. I haven't looked again at whether it's possible to increase this transfer rate, because I can't believe I would have set it to that speed if it had been possible to increase it back then (my PC would have been good for 115,200 Baud rate).

So you may find that 19,200 is the fastest possible. But I could very well be wrong.

prowler

PS. A1200 was not accelerated in either case.
I had 4 56k modems answering my bbs in the late 80ies.. sometime all 4 with people logged in.. all of them set to 19200

so the amiga was more than capable to run it but perhaps it was not possible to set higher..
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Old 30 July 2013, 11:56   #19
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AFAIR 1.79Mbps - but MC1488/1489 will affect speed (they are quite old and slew rate is limited) - perhaps replacing them with some modern hi speed RS232 voltage translator can help.

Quote:
Originally Posted by mc6809e View Post
Serial port send/receive buffers in chipram with their own DMA channels would have been very nice.
Copper can be used as Write DMA for serial (except OCS Agnus), for reading just CPU and pooling mode.

DMA is available for reading/writing with floppy - however speed is limited (RAW 500kbps - MFM coded 250kbps).
serial port is available also on CIA, also joystick ports can be used to input/output data (4 bit I/O)

Last edited by pandy71; 30 July 2013 at 14:08.
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Old 30 July 2013, 15:06   #20
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speed of the amiga serial port depends of the cpu
my A1200 020/28mhz is capable to transfer at 115200 in amiga explorer

but if I remove the turboboard of my A1200 is only capable of 38400
so basically for the max speed 115200 you need a 020/28mhz or a 030/25
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