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Amiga 2620/2630 Accelerator Hardware Technical Notes

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@database A26xxTechnicalNotes

@Index IndexNode
@author "Calum Tsang"
@$VER: A26xxTechnicalNotes Release 1 (10/96)
@font courier.font 13

@node Main

	Commodore Amiga 2620/2630 Accelerator Hardware Technical Notes Revision 1
	written and compiled by @{"Calum Tsang" link Calum} - October 1996

	@{"  " link Introduction} Introduction - Overview of the A26xx     

	@{"  " link Jumpers2620} Jumpers - Jumper Functions for A2620

	@{"  " link Jumpers2630} Jumpers - Jumper Functions for A2630 

	@{"  " link Memory} Memory - Memory Expansion for the A2620/2630

	@{"  " link ROM} ROM - Control ROM Revisions for the A26xx

	@{"  " link Overclocking} Overclocking - Speeding up the A26xx

	@{"  " link Problems} Problems - Common Troubles with A2620/2630

	The latest revision should be available at


@node Introduction "An overview of the Commodore Amiga 26xx accelerators..."

	This document is meant to provide information about the Commodore
Amiga 2620 and 2630 accelerator boards for the Amiga user community.  Every
week, another person on Usenet will ask, what are the jumpers on one of
these boards?  Comments and corrections are always welcome at my @{"email" link Calum}
address.  Thanks! 

	A lot of the information here is from Usenet and Internet sources:
For instance, many of the A2630 hardware fixes are from Stefan Tiemann, who
wrote a small AmigaGuide file about bugs such as reversed resistor packs,
etc.  Take a look at this on Aminet.  Also, many Usenet posters have sent
out the jumper specs, I've correlated those with Commodore's printed

System Overview
	With the advent of powerful 020/030 class workstations in the 80's
such as the Macintosh II and Sun 3/60, plus many third party expansion
options for the A2000 supplying 32 bit fast CPU extensions, Commodore
produced the first "official" accelerator board for the Amiga 2000 system,
the A2620 68020 CPU Accelerator.  Complete with 2 or 4MB of 32 bit local
RAM to the 020, plus a 68851 Memory Management Unit and a 68881 FPU Math
chip, the A2620 pushed the A2000 up to four times faster than a stock unit.
The entire board was clocked at 14 MHz, but the 68881 can be externally
clocked at any frequency, up to 100 MHz.

	A second board, the A2630, housed a 68030 chip, with integral MMU,
and a 68882 FPU at 25 MHz.  It's RAM expansion was similar to the 2630, but 
had the option of a 32 bit expansion slot on the back of the card, allowing 
for even more memory through third party products, such as the DKB2632 board.  
This board accelerates a stock machine 6-8 times faster.

	Both boards fit into the 86 pin expansion slot, and relieve the
68000 stock motherboard processor.  AutoConfiguring, these boards add in
their 32 bit RAM into 24 bit AutoConfig space as well, taking up part of
the 8MB limit.  However, this is a compatibility feature: when you disable
the 020/030, your RAM is still available to you.


@node Jumpers2620 "Jumper block settings for the A2620 board..."

Jumpers on the A2620
	ON means jumper in place, OFF means no jumper.

	J302 [OFF] - Set ON for operation on 4 layer, German A2000 4.0 

	J200 [UP]  - Set to DOWN position, to clock the 68881/68882 socket
		     through the external FPU Oscillator plug.

	J301 [OFF] - Set to ON for 4 MBytes of RAM, OFF for 2 MBytes, 
		     depending on your RAM configuration on your A2620.

	J303 [OFF] - Set to ON to disable all A2620 memory.

	J304 [OFF] - Set to ON to autoload AMIX (AmigaUNIX) off of disk
		     or tape.  Most Amiga users should set to OFF for

	J500 [ON]  - Sets RAM timing to 80 or 100 ns.


@node Jumpers2630 "Jumper block settings for the A2630 board..."

Jumpers on the A2630
	ON means jumper in place, OFF means no jumper.

	JP202[RIGHT]-Set to rightmost position to lock 030 and 882
		      together for 25 Mhz clock.  Set to left for
		      asychronous clock of the 68882.

	J301 [ON]   -Set to ON for 2MBytes of RAM, OFF for 4MBytes.

	J302 [OFF]  -Set to OFF for two layer motherboards, ON for
		     four layer, German 4.0 A2000 boards.  Basically,
		     jumper lets the system run with the 68030 when
		     the 68000 isn't socketed, which is the way it
		     should be with the old four layer A2000.

	J303 [OFF]  -Set to ON to disable all A2630 memory, to not
		     to AutoConfigure.

	J304 [OFF]  -Set to ON to autoload AMIX (AmigaUNIX) off of disk
		     or tape.  Most Amiga users should set to OFF for


@node Memory "Information about the memory on the A26xx accelerators..."

	The 020 and 030 CPUs benefit from local, high speed, 32 bit access
to a memory segment.  As a result, the A2620/2630 accelerators have either
2 or 4MBytes of RAM shipped on the right side of the board.

	On startup, the RAM is AutoConfigured into the 8MBytes of the
A2000's 24 bit AutoConfig space, so if you have 4MBytes on the A2630, you
can only have 4MBytes more on 16 bit RAM cards, an A2091, a Bridgecard,
etc.  There is a benefit of this, in that if you startup using the 68000
only, the RAM on the board is still available to you, unlike many
accelerator designs.

	There is a possibility of deAutoConfiguring the board and
reconfiguring the 32 bit RAM using AddRAM, but this really depends on each 

	To expand the board beyond 2MBytes, you'll need 16 chips of 414256
256Kx4 density, at minimum 100 ns.  If you want, you can use higher
performance 80 ns chips with these boards, with appropriate rejumpering
of the A2620.  The chips are in 20 pin, ZIP, Zigzag Inline Package, format,
in Page Mode access which are increasingly hard to find.  However, many 
A2386SX Bridgeboard users, have their first 1MByte segment to spare after 
upgrading from 5 to 8MBytes, so you may be able to coax them into getting 
their old 256K ZIPs.  They have to be soldered into the board, so you might
want to get your dealer to do the upgrade.

	As mentioned above, you can also use 16 bit AutoConfig expansion
cards to add more memory to the entire system, but many may desire to run
more 32 bit local memory to the 030.  The DKB2632 board, sold by DKB,
attachs to CN300 and CN301, and can hold up to 112MBytes of RAM for the
2630, using industry standard SIMMs.

	There was a hack to put SIMMs into the ZIP sockets, but it has been
removed from Aminet.  It included a board schematic and was share-hardware.


@node ROM "ROM Revisions of the A2620/2630..."

ROM Revisions
	The A2620/2630 boards have a set of EPROM chips, Read Only Memory,
which contain code for starting up the accelerator and integrating it into
the Amiga 2000 system.

	While there have been many ROM revisions for the A2620/2630 boards
over the past few years, the one everyone should be using is rev 7.0, the
latest and last from Commodore.  Why?  7.0 is the version that fully
supports 2.x and above of the AmigaOS.  While you can get away with 6.6,
7.0 is the official revision.  Both the A2620 and 2630 use the same ROM

	How can one go about getting these ROMs?  One way is to go to your
local dealer, and see if they have a pair.  If they don't, try a mail
order place.  If that doesn't pan out, you can copy the ROMs, anyone with a
ROM copier/burner can easily duplicate a pair of 7.0's for you.  This
assumes that you a) don't care about copyrights and b) have a nice friend
with 7.0's.  

	I don't see the copyright issue as a big deal, seeing as Commodore
is not giving proper support on these boards, AmigaTechnologies is very
much still in the air (and won't support them either) and getting these
ROMs is difficult by legal means anyways.  Of course, don't blame me for
bad advice.


@node Overclocking "Overclocking the 26xx..."

	The A2620 is NOT a board to overclock.  Why?  Because the main
timing is derived off of the A2000 motherboard, not the accelerator.  As a
result, you'd be hard pressed to reengineer the card to a new timing.
However, you can modify the FPU-replace it with a 68881, upclock with a new
4 pin TTL crystal etc.  Of course, when upclocking the FPU, remember to use
a chip rated for the speed you desire.  Anything else will burn out the
chip prematurely.

	The A2630, runs the CPU and FPU asynchronous to the main board,
meaning, it has it's own oscillator.  Now, as with any overclocking
discussion, it is well known that raising the timing of a chip over it's
rated spec, 25 MHz in this case can prematurely burn it out.  But with 
030/33's so cheap these days, you can replace the 030/25, and reclock the 
board at 33 MHz.  Dave Haynie has commented they had a 2630 working at
Commodore with a 32 Mhz oscillator, so the logic can handle it.

	It has been recommend by Stefan Tiemann that a 1K resistor from pin
10 to 14 of U300 on the A2630 when one goes above 25 Mhz.

	Overclocking a rated spec at a higher speed can result in system
instability-and crashes, even if the chip does start up properly.


@node Problems "Troubleshooting the A2620/2630 Accelerators..."

Common Problems and Troubleshooting
Many of the answers below were culled from Stefan Tiemann's A2630 Fix

Q: Why does my system not start?
A1:Your board is jumpered incorrectly.  Check out the @{"2620" link Jumpers2620}
   and @{"2630" link Jumpers2630} sections for help in 
   setting up your board.

A2:Your ROM Revision is incorrect for your OS ROM.  Read @{"the ROM Revision" link ROM} 
for more information.

A3:Your board could be dead.  Check all connections, seat chips firmly,
   and the CPU.  Faulty CPU connections may result in a yellow screen.

Q: I get sporadic crashes.
A1:Could be a bad RAM chip: use a RAM checker from Aminet.
   Or try using the memory monitor on the A2630: on reboot, hold down
   both mouse buttons, type Shift-M to get into the Monitor, then
   try i for Information on the system, then t 200000 600000 to test out
   a 4MByte board, and t 200000 400000 to test a 2MByte board.  I've
   never tried this, but it may be useful.  Thanks to Stefan Tiemann,
   [email protected] for this, it came from his A2630 Fix Guide.

A2:Could be flaky hardware. Check for cold solder joints and the like.

Q: Why is my 2091 so slow?
A1:It has no 16 bit RAM, and is in PIO mode, as a result.  Slap some
   16 bit RAM in 44256's onto it, or buy a PIO mode controller.

A2:U605 on the A2000 motherboard may be causing DMA problems: add a 1K
   resistor between pins 11 and 20 to correct this.
Q: I want to expand past 4MBytes 32 bit local FAST?
A: Buy a DKB2632.  Read the @{"Memory" link Memory} section about this

Q: Can I overclock this board <evil grin>?
A: the @{"Overclocking" link Overclocking} section first.

Other Problems
-Some A2630's have their CN300, CN301 connectors on backwards.  Desolder
 and resolder on the back side.

-Some A2630's have RP104, 105, 107 and 107 on backwards.  


@node Calum "More about Calum Tsang, that guy who's so excited, and just can't hide it..."

About the Author
	[email protected]		(Internex Online)
	[email protected]	(Kiwi Systems Toronto)

	Hi.  I'm a relatively abnormal guy living in Toronto, studying
Industrial Engineering at last check, whose owned Amigas since 1988! 
I own both A2620/2630 cards and really like the speed they afford,
especially for the low price they go for these days on the used market.

	The style of this package of Technical Notes was inspired by Warren 
Block's excellent A4000 Hardware Guide.  It's in a similar style, but also in 
the fashion of the A2090 Technical Notes package I started in 1992.  Thanks 
Warren for helping and getting me started.


@node IndexNode "Index"

  @{"Jumpers2620" link "Jumper Settings for the A2620"}
  @{"Jumpers2630" link "Jumper Settings for the A2630"}
  @{"Memory" link "Memory Expansion for the A26xx"}
  @{"Overclocking" link "Overclocking the A26xx"}
  @{"ROM" link "ROM Revisions for the A26xx"}
  @{"Troubleshooting" link "Troubleshooting the A26xx"}