ST vs Amiga : advantages/disadvantages

Troubles with your machine? Just want to speak about the latest improvements? This is the place!

Moderators: Mug UK, Zorro 2, spiny, Greenious, Moderator Team

Post Reply
User avatar
galvatron1983
Atari freak
Atari freak
Posts: 71
Joined: Sun Apr 08, 2012 12:30 pm
Location: East London, UK
Contact:

ST vs Amiga : advantages/disadvantages

Post by galvatron1983 »

This has been done to death Im sure, but I would like to see every-bodies thoughts on where the ST was superior to the Amiga and where it wasn't so hot...

These are my thoughts as a newcomer to the ST scene:

Advantages:

Better display resolution support, especially in monochrome
Slightly better frame-rates, and rendering on 3D polygon games
Much better MIDI/music production support
Easier to upgrade RAM (on certain models)
Faster clocked 68000



Disadvantages:

Lower quality (almost 8Bit like!) BGM in games
Only 16 colours onscreen at once compared to 32
Lack of blitter support initially
Lack of STE enhanced titles
Inferior video editing tools
Jerkier scrolling on certain games vs Amiga versions


As a big ST gamer, a lot of these are game related, and some of them are possibly down to the game makers themselves and shoddy coding as opposed any inherent problem with ST hardware itself.
Image
User avatar
dma
Atari God
Atari God
Posts: 1160
Joined: Wed Nov 20, 2002 11:22 pm
Location: France
Contact:

Re: ST vs Amiga : advantages/disadvantages

Post by dma »

A major advantage of ST over Amiga, is the standard disk structure it can use when formating.
I remember having to transfer files (downloaded from the web on PC) with "DOS2DOS" software on Amiga (which allow reading standard PC formatted disk on the Amiga drive, very slowly...), such a pain.
User avatar
nativ
Fuji Shaped Bastard
Fuji Shaped Bastard
Posts: 4106
Joined: Mon Jul 30, 2007 10:26 am
Location: South West, UK

Re: ST vs Amiga : advantages/disadvantages

Post by nativ »

galvatron1983 wrote:This has been done to death Im sure, YEP!!

Disadvantages:

Lower quality (almost 8Bit like!) BGM in games

Real chip YM over samples or on the STe Paula emulation ( and better 25/50hz)

Only 16 colours onscreen at once compared to 32

Standard interface colours? then there is Spectrum 512 / Quantum Paint / PhotoChrome 4096/19200

Lack of blitter support initially
When was the Blitter introduced? 1988?? The Amiga was a desktop PC initially in a different price bracket?

Lack of STE enhanced titles
Depends what you want, gaming had moved over to consoles in the main at the time of the STe

Inferior video editing tools, Well yep, the St can do Video titling it has Videomaster Vidi ST same as amiga, and the STe has a Genlock but it was never?? used!

Jerkier scrolling on certain games vs Amiga versions

Well on the Amiga the coders could be lazy, and they would have to work for decent scrolling on the st, so only good coders got this right, STe no argument.

As a big ST gamer, a lot of these are game related, and some of them are possibly down to the game makers themselves and shoddy coding as opposed any inherent problem with ST hardware itself.
Atari STFM 512 / STe 4MB / Mega ST+DSP / Falcon 4MB 16Mhz 68882 - DVD/CDRW/ZIP/DAT - FDI / Jaguar / Lynx 1&2 / 7800 / 2600 / XE 130+SD Card // Sega Dreamcast / Mega2+CD2 // Apple G4

http://soundcloud.com/nativ ~ http://soundcloud.com/nativ-1 ~ http://soundcloud.com/knot_music
http://soundcloud.com/push-sounds ~ http://soundcloud.com/push-records
User avatar
1st1
Atari Super Hero
Atari Super Hero
Posts: 885
Joined: Mon May 07, 2012 11:48 am

Re: ST vs Amiga : advantages/disadvantages

Post by 1st1 »

:megaphone: 20 years back this was topic on flame wars ... :cheers:

Let me add my comments... :contract:
galvatron1983 wrote:This has been done to death Im sure, but I would like to see every-bodies thoughts on where the ST was superior to the Amiga and where it wasn't so hot...

These are my thoughts as a newcomer to the ST scene:

Advantages:

Better display resolution support, especially in monochrome

The monochrome mode was really attracting a lot of peoples, specially for serious working with a computer cheaper than a PC or Mac, and even on any expensive PC there was nothing compareable.
The color modes of original ST / Mega ST were far behind the Amiga 500/1000, the ECS Amigas were again a far step away. Even the STE / Mega STE could not compete. One thing missing was hardware overscan support - no Idea why Atari did not, the AutoSwitch-Overscan patch was so simple... Hardware scrolling was also much easier on Amiga, ST did not have Sprite support, etc.
Slightly better frame-rates, and rendering on 3D polygon games

This is only for CPU rendered graphics, because the 68000 in Amiga runs only at 7,14 MHz, and in ST/STE in 8 MHz. This is the reason also if you link an Amiga 500 to an Atari ST/STE and you load Popoulos game on both, playing together, that the person on the ST alwas wins, as he can do a few more actions in the same time... The Amiga Blitter was more powerfull than the one in the ST/STE.
Much better MIDI/music production support

It was also possible to add a Midi-Interface to the Amiga, but it was not factory built in, that was a real advantage for the ST and successors as this started the availability of a quite cheap hardware for midi sequencers and so. Without Atari, companies like Steinberg would maybe not exist today. On the other hand, the digisound of the Paula soundchip of the Amiga was many steps ahead of the YM chip in the ST. Also the STE-DMA-Sound could not support four voices in stereo without software tricks.
Easier to upgrade RAM (on certain models)

Upgrading a 260/520/1040 ST's memory is not that easy... In A500 you just could plugin a 512 MB card in the bottom side memory slot and it was done. ICD offered an addon card for A500/500+ with up to 4.5 MB.
Faster clocked 68000


Disadvantages:

Lower quality (almost 8Bit like!) BGM in games

That's what I wrote above, even C-64's 6581 soundchip was better than the YM.
Only 16 colours onscreen at once compared to 32

Don't forget Amiga's HAM mode with 4096 colors. (But there were a few programs supporting 512 colors on ST, Spectrum512 and some demos for example.)
Lack of blitter support initially

Some early 1040 were even hard to update with the blitter, the socket was there, but some modifications to the PCB had to be done... I did that for my 1040, but when I added the Pak68/2 I found out that the CPU is faster than the blitter...
Lack of STE enhanced titles

STE came too late, it was already in Atari's drawer for a while when it was released to the public... The normal ST still sold well enough in Tramil's opinion to release the STE earlyer...
Inferior video editing tools

... because of no Genlock support of the first STs. Only STE/Mega STE supported this, but still no hardware overscan, who wants to edit videos with borders...???
Jerkier scrolling on certain games vs Amiga versions
That's because of the Amiga Blitter and better (horicontal!) hardware scrolling.
As a big ST gamer, a lot of these are game related, and some of them are possibly down to the game makers themselves and shoddy coding as opposed any inherent problem with ST hardware itself.
As a conclusion I wonder how we decided for ST instead of Amiga at that time... but there are many more points which are interesting for the decision which computer was the better one... Let me add some points of views:

1. Atari:

- The monochrome mode and it's 70 Hz SM124 was legendary, a lot of interesting applications were based on this, like Calamus, Signum, Adimens, Midi-Software. On Amiga there was nothing similar.
- The operating system (TOS/GEM) was interesting by itself as it was very close to PC, same file system, (almost) same graphical user interface (PC-GEM by DRI), similar programming (compare GEMDOS()-functions with INT13h on MS-DOS - they are the same except of little/big endian data format! (Microsoft talked to Atari to implement Windows on ST instead of GEM, but it would have taken too long, so the decision went on GEM)
- ACSI interface to add easily an harddrive. As ACSI was a simplified SCSI interface and ATARI themselves showed the world how to make a full SCSI interface of that (see SH204 internals) a lot of 3rd partiy SCSI adapters and drive appeared. Adding a harddisk to an Amiga 1000/500 was much more difficult.

2. Amiga
- The operating system was very interesting, because of Multitasking and object orientation ("cd disk0:" could also be a harddisk folder assigned to disk0:)
- The Amiga-OS 2.0 and later was looking much nicer than even TOS 4.0 of the Falcon. I mean uncustomized desktops!)
- With the A2000, and later A3000, A4000 Commodore offered much more flexible systems as Atari with the Mega-ST/STE, TT and falcon. Commodore defined it's on add on card design with Zorro-Slots for add on cards, following the idea of PC's ISA-Slots. Add-on hardware on an ST, Mega-ST, Mega-STE, TT or Falcon is not that comfortable.

Looking back from 20 years ahead we can say, that both systems were loosers against the PC, the PC took all the advantages of ST and Amiga hardware and software (without beeing compatible to them), but both, Atari and Amiga, instead of the PC, they still have style, flair and charm. 20 years in the future nobody will cry for a PC from today.
Power without the Price. It's not a bug. It's a feature. _/|\_ATARI

1040STFM in PC-Tower (PAK68/2, OvrScn, 4 MB, 1GB SCSI, CD-ROM...) * 3x Falcon 030 * 3x TT030 * many 260 /520/1040ST(F)(M)(+) * 520/1040STE * many Mega ST * 2x Mega STE * Stacy * STBook * 2x SLM605 * 3x SLM804 * SMM804 * SH 204/205 * Megafile 30/44/60 * SF314 * SF354 * 5x Pofo * PC3 * ...
User avatar
1st1
Atari Super Hero
Atari Super Hero
Posts: 885
Joined: Mon May 07, 2012 11:48 am

Re: ST vs Amiga : advantages/disadvantages

Post by 1st1 »

I forgot one very important point for Atari, maybe the most important one:

The guys (and a few girls) in the Atari Demo scene were much cooler and smarter as the Amiga community. Amiga community guys were all fat and lazy, pale skin, arrogant and they just programmed what the hardware could do by itself, just Lamers! The Atari guys coded real cool things what the hardware was not designed to do, like horicontal scrolling, 512 colors, overscan, digital sound, etc, and always ready for some good jokes. Really smart guys, just remembering some dutch, swedish, french and german guys at the Atari fair in Düsseldorf, oh that was fun! :cheers:

I still remember Sam Tramil on CeBit (I think it was in 1990), standing in front of an STE on the Atari booth and watching the SoWatt-demo main menu, and telling "that's impossible...".... Oh that was so cool!
Power without the Price. It's not a bug. It's a feature. _/|\_ATARI

1040STFM in PC-Tower (PAK68/2, OvrScn, 4 MB, 1GB SCSI, CD-ROM...) * 3x Falcon 030 * 3x TT030 * many 260 /520/1040ST(F)(M)(+) * 520/1040STE * many Mega ST * 2x Mega STE * Stacy * STBook * 2x SLM605 * 3x SLM804 * SMM804 * SH 204/205 * Megafile 30/44/60 * SF314 * SF354 * 5x Pofo * PC3 * ...
User avatar
DarkLord
Fuji Shaped Bastard
Fuji Shaped Bastard
Posts: 4495
Joined: Mon Aug 16, 2004 12:06 pm
Location: Prestonsburg, KY - USA
Contact:

Re: ST vs Amiga : advantages/disadvantages

Post by DarkLord »

1st1 wrote: :megaphone: 20 years back this was topic on flame wars ... :cheers:
As a conclusion I wonder how we decided for ST instead of Amiga at that time...
Let's not forget another very powerful argument - price, at least initially.

I was using an 800XL when the ST was released, with the Amiga following not
long after.

Here, I purchased an Atari 520ST, 720k floppy drive, and monitor from CDW for
$999.00, with some software they threw in.

The Amiga 1000 base unit here at that time was over $1500.00, with no monitor.

Easy choice for me. :)
Welcome To DarkForce! http://www.darkforce.org "The Fuji Lives.!"
Atari SW/HW based BBS - Telnet:darkforce-bbs.dyndns.org 520
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

galvatron1983 wrote:This has been done to death Im sure, but I would like to see every-bodies thoughts on where the ST was superior to the Amiga and where it wasn't so hot...

As a big ST gamer, a lot of these are game related, and some of them are possibly down to the game makers themselves and shoddy coding as opposed any inherent problem with ST hardware itself.
WHAT?! "Shoddy coding"?

Atari ST programmers worked very hard to do a lot with very little. The ST wasn't built to be a games machine and it isn't much more than a CPU attached to a simple frame buffer. It took an absolutely heroic programming effort to get decent frame rates for games. Don't blame hard-working programmers for low frame rates.

The Amiga had 128 pixels worth of hardware sprite data per scanline, hardware scrolling of two independent playfields including overlay with transparency, a blitter with line draw and area fill, and a separate coprocessor synced to the video beam location with its own instruction set that could drive it all (including the blitter) without CPU intervention.

How the hell is a programmer supposed to emulate all that in software using an 8MHz 68000? ST programmers were not lazy! They had a very tough job.

You know who were lazy? Amiga programmers doing conversions from ST games. Amiga owners cried constantly about programmers ignoring the Amiga's graphics hardware when converting games.

The biggest advantage the ST had over the Amiga was simply that it was more affordable and accessible to the average person.

The Amiga had the advantage in nearly everything else, but you had to paid much more money for that.
User avatar
1st1
Atari Super Hero
Atari Super Hero
Posts: 885
Joined: Mon May 07, 2012 11:48 am

Re: ST vs Amiga : advantages/disadvantages

Post by 1st1 »

Yes, Amiga 1000 was quite expensive, but the correct Answer was the A500 and that was competitive to a 1040ST, even with the 512MB add on card.

And I forgot to mention another advantage of the Amiga over ST: To be able to attach up to four floppy drives ... and XCOPY ... what was able to use all four floppys, what was very usefull to share latest games with three friends at the same time it even was able to copy every copy protection for the ST... This was the reason for me to get one...
Power without the Price. It's not a bug. It's a feature. _/|\_ATARI

1040STFM in PC-Tower (PAK68/2, OvrScn, 4 MB, 1GB SCSI, CD-ROM...) * 3x Falcon 030 * 3x TT030 * many 260 /520/1040ST(F)(M)(+) * 520/1040STE * many Mega ST * 2x Mega STE * Stacy * STBook * 2x SLM605 * 3x SLM804 * SMM804 * SH 204/205 * Megafile 30/44/60 * SF314 * SF354 * 5x Pofo * PC3 * ...
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

1st1 wrote:Yes, Amiga 1000 was quite expensive, but the correct Answer was the A500 and that was competitive to a 1040ST, even with the 512MB add on card.

And I forgot to mention another advantage of the Amiga over ST: To be able to attach up to four floppy drives ... and XCOPY ... what was able to use all four floppys, what was very usefull to share latest games with three friends at the same time it even was able to copy every copy protection for the ST... This was the reason for me to get one...
The Amiga did have the ability to DMA raw bit patterns from disk to memory and back, making it capable of reading and writing just about any format.

It made piracy much easier with the Amiga -- and probably helped kill the platform in the process.
User avatar
1st1
Atari Super Hero
Atari Super Hero
Posts: 885
Joined: Mon May 07, 2012 11:48 am

Re: ST vs Amiga : advantages/disadvantages

Post by 1st1 »

Yes, this was possible because the Amiga did not have a floppy controller like the WD1772 in the ST (or any PC). The shugart bus data signals just went into the IO chip of the Amiga (8520? It was a 6526 for 8 Mhz), the io chip just got the raw bits from the floppy head. No chipset accelerated MFM encoding like in ST, but software GCR encoding like the 1541 floppy of the C-64. But that brings me to another little advantage of the ST over Amiga: DMA on floppy drive, Amiga used "PIO" instead, more processor intensive.
Power without the Price. It's not a bug. It's a feature. _/|\_ATARI

1040STFM in PC-Tower (PAK68/2, OvrScn, 4 MB, 1GB SCSI, CD-ROM...) * 3x Falcon 030 * 3x TT030 * many 260 /520/1040ST(F)(M)(+) * 520/1040STE * many Mega ST * 2x Mega STE * Stacy * STBook * 2x SLM605 * 3x SLM804 * SMM804 * SH 204/205 * Megafile 30/44/60 * SF314 * SF354 * 5x Pofo * PC3 * ...
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

1st1 wrote::megaphone: 20 years back this was topic on flame wars ... :cheers:

Let me add my comments... :contract:
galvatron1983 wrote: Slightly better frame-rates, and rendering on 3D polygon games
This is only for CPU rendered graphics, because the 68000 in Amiga runs only at 7,14 MHz, and in ST/STE in 8 MHz. This is the reason also if you link an Amiga 500 to an Atari ST/STE and you load Popoulos game on both, playing together, that the person on the ST alwas wins, as he can do a few more actions in the same time... The Amiga Blitter was more powerfull than the one in the ST/STE.
Not just more powerful, but faster it turns out, even though the ST has a shorter memory cycle time. The Amiga blitter (and CPU for that matter) could use any available memory cycle. Atari made a huge mistake, IMO, in forcing their blitter to talk to memory as if it were the 68000. I understand their reluctance to redesign the MMU, but allowing the blitter to use any available memory cycle would have made it more competitive with the Amiga's blitter.

Comparing NTSC systems:

Atari cpu cycles/frame = 508*263 = 133,604 cycles. There are 133,604/2= 66802 memory accesses/frame. CPU/blitter gets half of those so 66802/2

= 33,401 CPU or blitter memory accesses per frame. Shifter/memory refresh gets the other 33,401 available.

Amiga has 226*263 = 59,438 memory accesses/frame if no DMA or memory refresh. Subtracting memory refresh cycles and 16 color 320x200 screen DMA leaves 59,438 - (263*4+200*20*4)

= 42,386 accesses per frame. Audio can take up to (4*263)=1052/frame. Using the copper to set display hardware display registers might take 20/frame. Subtracting all that and you still have 42386-1052-20

= 41,314 accesses per frame for CPU/blitter.

A simple blitter copy is going to be 23% faster on the Amiga.
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

1st1 wrote:Yes, this was possible because the Amiga did not have a floppy controller like the WD1772 in the ST (or any PC). The shugart bus data signals just went into the IO chip of the Amiga (8520? It was a 6526 for 8 Mhz), the io chip just got the raw bits from the floppy head. No chipset accelerated MFM encoding like in ST, but software GCR encoding like the 1541 floppy of the C-64. But that brings me to another little advantage of the ST over Amiga: DMA on floppy drive, Amiga used "PIO" instead, more processor intensive.
On the Amiga, an entire track was read or written using DMA, and MFM encoding/decoding WAS accelerated -- by using the blitter.

There were plenty of spare odd memory cycles available for the blitter to make this mostly free.
User avatar
DarkLord
Fuji Shaped Bastard
Fuji Shaped Bastard
Posts: 4495
Joined: Mon Aug 16, 2004 12:06 pm
Location: Prestonsburg, KY - USA
Contact:

Re: ST vs Amiga : advantages/disadvantages

Post by DarkLord »

IF you wanted to pirate/copy stuff on the ST, it was entirely possible though. A cheap
hardware and software mod, the Blitz cable, which bypassed and fooled the WD1772
chip, made it drop dead easy....
Welcome To DarkForce! http://www.darkforce.org "The Fuji Lives.!"
Atari SW/HW based BBS - Telnet:darkforce-bbs.dyndns.org 520
User avatar
Cyprian
10 GOTO 10
10 GOTO 10
Posts: 2000
Joined: Fri Oct 04, 2002 11:23 am
Location: Warsaw, Poland

Re: ST vs Amiga : advantages/disadvantages

Post by Cyprian »

mc6809e wrote:Atari cpu cycles/frame = 508*263 = 133,604 cycles. There are 133,604/2= 66802 memory accesses/frame. CPU/blitter gets half of those so 66802/2

= 33,401 CPU or blitter memory accesses per frame. Shifter/memory refresh gets the other 33,401 available.

Amiga has 226*263 = 59,438 memory accesses/frame if no DMA or memory refresh. Subtracting memory refresh cycles and 16 color 320x200 screen DMA leaves 59,438 - (263*4+200*20*4)

= 42,386 accesses per frame. Audio can take up to (4*263)=1052/frame. Using the copper to set display hardware display registers might take 20/frame. Subtracting all that and you still have 42386-1052-20

= 41,314 accesses per frame for CPU/blitter.

A simple blitter copy is going to be 23% faster on the Amiga.

yes, Amiga's blitter can some really nice features, but in case of filling memory (e.g. from halftone registers) Atari's blitter is 11% faster :P
Both blitters can write data to destination address every 4th CPU cycle. In case of ST - 8Mhz / 4 = 2MB/s; A500 - 7.1 / 4 = 1.78MB/s
mc6809e wrote:On the Amiga, an entire track was read or written using DMA, and MFM encoding/decoding WAS accelerated -- by using the blitter.

There were plenty of spare odd memory cycles available for the blitter to make this mostly free.
yes, but finally during reading/writting to disk, Amiga's blitter is locked, and Atari's blitter still can fill/copy with almost full speed.
Mega ST 1 / 7800 / Portfolio / Lynx II / Jaguar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / Lynx Multi Card / LDW Super 2000 / XCA12 / SkunkBoard / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net / AT Speed C16
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

Cyprian wrote: yes, Amiga's blitter can some really nice features, but in case of filling memory (e.g. from halftone registers) Atari's blitter is 11% faster :P
Both blitters can write data to destination address every 4th CPU cycle. In case of ST - 8Mhz / 4 = 2MB/s; A500 - 7.1 / 4 = 1.78MB/s
Admittedly when the Amiga's blitter is using just the D channel, it skips every other available memory cycle -- leaving every other cycle available to the CPU to help fill memory. Using both the blitter and CPU to fill memory at the same time makes the Amiga 20% faster. This isn't possible with the ST blitter since it competes for even cycles with the CPU and blocks it.

Cyprian wrote: yes, but finally during reading/writting to disk, Amiga's blitter is locked, and Atari's blitter still can fill/copy with almost full speed.
No. The blitter isn't locked. The blitter can run at the same time raw bits are DMA'd into and out of memory.

On the st, DMA from/to the FDC will steal even memory cycles from the CPU/blitter, however. (It's not much at all though).
mdivancic
Captain Atari
Captain Atari
Posts: 286
Joined: Fri Jan 15, 2010 11:59 pm
Location: Lyman, Maine USA

Re: ST vs Amiga : advantages/disadvantages

Post by mdivancic »

I use both, and like them both. They sit side by side in my computer room. To me the thing that amazes me the most is that people are still making new hardware for all retro computers! I've got a SuperVidel on order for my Falcon and will soon have a Indivision AGA MK2 ordered for my Amiga. Two cool new hardware upgrades for 14+ year old computers, how cool is that?

My A4000T was made in 1998 (though designed much earlier) and my Falcon would have been made between 1992-93.
Mikey
Atari STacy 1
Atari TT030, CaTTamaran, 4 MB ST-Ram, 16 MB TT-RAM, ECL2VGA
Atari 800XL
Amiga 2000HD
Commodore 128D, 1084S monitor, RAMLink, CMD 4.1GB Hardrive
Commodore C64 Reloaded Mk2
Commodore SX-64
User avatar
bullis1
Fuji Shaped Bastard
Fuji Shaped Bastard
Posts: 2301
Joined: Tue Dec 12, 2006 2:32 pm
Location: Canada
Contact:

Re: ST vs Amiga : advantages/disadvantages

Post by bullis1 »

On ST you never get any RAM fragmentation warnings, which drove me up the wall in Workbench (along with the constant floppy access [and the horribly incompatible disk format]).

Amiga had great support from software houses though (game-wise).
Member of the Atari Legend team
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

bullis1 wrote:On ST you never get any RAM fragmentation warnings, which drove me up the wall in Workbench (along with the constant floppy access [and the horribly incompatible disk format]).
From what I've heard, the DOS of the Amiga was a quick 6 week hack written in BCPL and this was behind 90% of the problems.
User avatar
Frank B
Atari God
Atari God
Posts: 1029
Joined: Wed Jan 04, 2006 1:28 am
Location: Boston

Re: ST vs Amiga : advantages/disadvantages

Post by Frank B »

Cyprian wrote:
mc6809e wrote:Atari cpu cycles/frame = 508*263 = 133,604 cycles. There are 133,604/2= 66802 memory accesses/frame. CPU/blitter gets half of those so 66802/2

= 33,401 CPU or blitter memory accesses per frame. Shifter/memory refresh gets the other 33,401 available.

Amiga has 226*263 = 59,438 memory accesses/frame if no DMA or memory refresh. Subtracting memory refresh cycles and 16 color 320x200 screen DMA leaves 59,438 - (263*4+200*20*4)

= 42,386 accesses per frame. Audio can take up to (4*263)=1052/frame. Using the copper to set display hardware display registers might take 20/frame. Subtracting all that and you still have 42386-1052-20

= 41,314 accesses per frame for CPU/blitter.

A simple blitter copy is going to be 23% faster on the Amiga.

yes, Amiga's blitter can some really nice features, but in case of filling memory (e.g. from halftone registers) Atari's blitter is 11% faster :P
Both blitters can write data to destination address every 4th CPU cycle. In case of ST - 8Mhz / 4 = 2MB/s; A500 - 7.1 / 4 = 1.78MB/s
mc6809e wrote:On the Amiga, an entire track was read or written using DMA, and MFM encoding/decoding WAS accelerated -- by using the blitter.

There were plenty of spare odd memory cycles available for the blitter to make this mostly free.
yes, but finally during reading/writting to disk, Amiga's blitter is locked, and Atari's blitter still can fill/copy with almost full speed.

The ST one even has some features the Amiga one lacks. Smudge mode for hflipping a bitmap or magnification it by 2x 4x 8x 16x.
It also has a much wider address range than the Amigas. The entire 24 bit range in the case of the Falcon. Filling memory is faster than the Amiga, filling with halftone is more elegant than the Amiga. Larger blits are possible too. Much larger than OCS. The ST can even bang hardware registers with it for effects like blitter plasma. There's no slow down from bitplane DMA.
The ST has a nice blitter for sure. I seriously hope nobody is going to repeat the false statement that the ST blitter has no barrel shifter! In any case the jaguar blitter is the best :)
User avatar
FedePede04
Atari God
Atari God
Posts: 1215
Joined: Fri Feb 04, 2011 12:14 am
Location: Denmark
Contact:

Re: ST vs Amiga : advantages/disadvantages

Post by FedePede04 »

Atari ST the mfp 68901.
Atari will rule the world, long after man has disappeared

sometime my English is a little weird, Google translate is my best friend :)
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

Frank B wrote: There's no slow down from bitplane DMA.
It would be more accurate to say that the ST's blitter can't speed up when there' no bitplane DMA. On the Amiga, the blitter can run at double speed by using both odd and even memory cycles, if they're available -- while the background color is displayed in the overscan areas, for example. On the ST, the MMU prevents the CPU/blitter from any memory access during odd cycles even if there is nothing to display.
User avatar
Frank B
Atari God
Atari God
Posts: 1029
Joined: Wed Jan 04, 2006 1:28 am
Location: Boston

Re: ST vs Amiga : advantages/disadvantages

Post by Frank B »

It all depends on what else the chip set is doing on the amiga. The St blitter isn't slow. It will clear at 80 000 bytes a pal frame and copy at half that. A generalised bit copy on the Amiga takes 8 clocks per word if bits in the destination need protected before you take into account dma contention. On the St that's eight with no contention for the body and 12 for any fringe. At eight MHz not seven.
Sent from my Galaxy Nexus using Tapatalk 2
User avatar
Frank B
Atari God
Atari God
Posts: 1029
Joined: Wed Jan 04, 2006 1:28 am
Location: Boston

Re: ST vs Amiga : advantages/disadvantages

Post by Frank B »

Pity the end masks on the Amiga affect the a channel and not the b or the generalised blit would be faster. I like the Amiga a lot. I think it's a work of art. I like the St too. The St blitter is nice IMHO

Sent from my Galaxy Nexus using Tapatalk 2
User avatar
1st1
Atari Super Hero
Atari Super Hero
Posts: 885
Joined: Mon May 07, 2012 11:48 am

Re: ST vs Amiga : advantages/disadvantages

Post by 1st1 »

mc6809e wrote:
bullis1 wrote:On ST you never get any RAM fragmentation warnings, which drove me up the wall in Workbench (along with the constant floppy access [and the horribly incompatible disk format]).
From what I've heard, the DOS of the Amiga was a quick 6 week hack written in BCPL and this was behind 90% of the problems.
Atari TOS also was developed under high pressure in short time - most of the time without (reliable) working hardware, very buggy until 1.04.

Read yourself "The Atari ST, Part 1+2"
http://www.dadhacker.com/blog/?p=995
http://www.dadhacker.com/blog/?p=1000
Power without the Price. It's not a bug. It's a feature. _/|\_ATARI

1040STFM in PC-Tower (PAK68/2, OvrScn, 4 MB, 1GB SCSI, CD-ROM...) * 3x Falcon 030 * 3x TT030 * many 260 /520/1040ST(F)(M)(+) * 520/1040STE * many Mega ST * 2x Mega STE * Stacy * STBook * 2x SLM605 * 3x SLM804 * SMM804 * SH 204/205 * Megafile 30/44/60 * SF314 * SF354 * 5x Pofo * PC3 * ...
mc6809e
Captain Atari
Captain Atari
Posts: 159
Joined: Sun Jan 29, 2012 10:22 pm

Re: ST vs Amiga : advantages/disadvantages

Post by mc6809e »

Frank B wrote:It all depends on what else the chip set is doing on the amiga. The St blitter isn't slow. It will clear at 80 000 bytes a pal frame and copy at half that. A generalised bit copy on the Amiga takes 8 clocks per word if bits in the destination need protected before you take into account dma contention. On the St that's eight with no contention for the body and 12 for any fringe. At eight MHz not seven.
Clearing memory on the Amiga is actually faster than 80,000 bytes/pal frame if the CPU is used to clear about 1/3rd of memory while the blitter clears the other 2/3rds. Using just the blitter, the clear rate is 70,738 bytes per pal frame (as expected given the clock rate). But that leaves 16,865 memory accesses available after subtracting bitplane DMA since a D channel clear uses only every other memory access. Using the CPU's MOVEM instruction in parallel with the blitter allows us to clear another 30,000+ bytes giving a clear rate of over 100,000 bytes per pal frame.

And for the rectangular copy I think you're overestimating the effect of contention on the Amiga and ignoring the problems of running the ST's blitter in HOG mode.

For a generalized rectangular bit copy of the sort you're talking about (no transparency or holes in the middle of the bitmap), 2 of the 8 cycles per copy are left open and are free from contention. The other 6 cycles can contend, but this happens half of the time during bitplane fetches. This means a maximum of 12 cycles are required per copy while 4 bitplanes are fetched during the display of a 16 color playfield. If hardware sprites are turned off and there's no disk DMA, though, 13 copies of 8 cycles per copy can occur during hblank and overscan. A total of 42 copys per active scanline can happen over 452 cycles. That's an average of 10.72 cycles per copy.

But that's during active scanlines. For an NTSC system, there are another 62 blank lines where the blitter can run nearly contention-free. Each of these lines permit 54.5 copies at just a fraction over 8 cycles per copy. This gives an average of 10.05 cycles/copy/frame on the Amiga. The number is even lower on a PAL system.

Factoring in clockrate, the ST's blitter is faster for copying rectangular bitmaps >16 pixels wide, but only by completely blocking the CPU's access to memory. The Amiga has an Advantage in that for 2 of the 8 cycles the blitter is performing the copy, the CPU can perform a memory access. There are 12 cpu accesses available during an active scanline, and 56 such cpu accesses during each vertical overscan scanline. This allows the CPU to process interrupts and perform other operations while the blitter is running.

Now consider the ST's blitter. A large copy is going to block interrupts and halt the CPU if HOG is enabled. If HOG is disabled, the blitter is forced to run at half-speed.

And all this assumes that the Amiga programmer can't be bothered to do 3 separate blits for the copy. If we allow the Amiga programmer to blit the center and the two fringes separately, we can take advantage of the Amiga's 4 cycles per copy speed for the center section. It's true that contention will happen much more often during such a copy, but even with contention, 69 copies can occur during 452 cycles of an active scanline. This gives an average of 6.6 cycles/copied word. For the vertical overscan areas the speed is nearly 4 cycles per copied word.

Even the copy speed of the fringes can be sped up if we simply allow 3 blits. We can set the mask for A as usual, but load B's data register with the mask for C. We use the logic function D=BC+A. Since B's DMA channel is turned off, copying the fringe occurs at 6 cycles per copy. Again, contention is an issue, but it's never worse than 12 cycles per fringe area copy and it is often better.
Post Reply

Return to “Hardware”