Trying to get an A2620 to work, looking for experience/ideas/documentation/schematics

07 May 2010, 01:45

Hello all.

I'm new to Amiga, and new on this board and found several hints here already - thank you.

Now, I've got a possibly defective A2620 marked 7-14-88 A/W 312831 REV 3 which I want to use in an Amiga 2000, board B2000 rev 4.1, kickstart 1.2 (but apparently with a MOS 8373 or so Gary? IC).

The A2620 has 0 RAM installed, and the seller on ebay advertised it as producing a "green screen" on his A2000.

In my system however, the card doesn't get that far. When it is plugged in, the monitor stays black on power up (with one slighly brighter line at the top of the screen).

--

I don't have a keyboard yet, but a mouse - and pressing any combination of mouse buttons during/after bootup doesn't change a thing.

The A2620 came wrapped in kind of thin plastic film that you'd use in the kitchen instead of usual electrostatic-protective-plastic-bags, so maybe it has been damaged on the way. I did some basic hardware testing:

Apparently, the 68020 CPU never gets it's (locally on A2620 generated) -RESET pin changed to high logic level, so I think that CPU doesn't start running, but the 68000 in the motherboard keeps wating for it to go on.

The 68881, however, has a reset signal that goes up shortly after powerup, just like the 68000 on the motherboard; both probably use the same signal.

So I think the problem might most probaly lie in the PALs (maybe in handling bus arbitration between CPUs or A2620-local reset generation for 68020) (or in the ability of this card to run at all with my A2000).

If I remove the MC68020, 68881, 68851, the ROMs, and all the PALs from the card - nevertheless, when it is plugged into the Amiga 2000, that one only shows a black screen upon power up.

I tried many (maybe all) possible jumper configurations on the A2620.

I've also confirmed that my motherboard bus slot has some rather plausible signals on all pins. The A2000 RTC battery was recently removed, with slightly discoloured areas on board seen, one pin of CPU slot showed blue stuff - that was cleaned, pin and neighbouring pins measured, should all still work.

I've also confirmed that all ICs on the A2620 have correct power (both Vcc and GND), including the MC68xxx ICs. I can't see obviously defective leads on that board and I've successfully tested some doubtful lines to be ok.
I've re-fixed a resistor on the back of the board that had been removed using photos in the WWW as a guide.

All 74xx ICs on the A2620 seem to work (as far as I can check without removing/without using a logic analyzer). I also checked (only) the simple functions of (only) a few PALs coarsely: I found that some xxxxxx.OE signals *may* not work as I would expect from the .PLD files from Haynes. Specifically, the output of these lines is never *disabled*: U306 ABG.OE and U305 MEMSEL.OE. And *maybe* one or two input signals may work in the opposite polarity from what I expect: U305 !BOSS->TRISTATE, and !BEER/!BERR. But - that might all be unexpected function of the PALs, or my wrong interpretation of the .PLD files or of my findings :-), or the files at Haynes would describe other versions of the PALs though they match the numbers on the ICs). And I don't know by now whether a PAL can just lose its capability to disable its output and perform all other functionality quite as expected?

Well - now I'm severely over my intended time budget, and a bit out of ideas (apart from firing up a logic analyzer which I will probably NOT do anytime soon for this board).

However - before I put the card aside for a long time: Might anybody on this forum...

...have run the A2620 without 32-Bit-RAM installed (I set the appropriate Jumper to indicate zero RAM to be used on the board)? Is that possible at all?

...have run the A2620 in the B2000 rev 4.1 board?
...with that MOS Gary instead of the ...older...Toshiba?...

...have run the A2620 without a keyboard on the A2000? Might that stop it from booting?!

...possibly know where to get the A2620 manual properly describing the function of jumpers 202, 201 (or *all* jumpers)? [It has more, and differently named jumpers than the A2630, and I haven't found docs though I've searched extensively.]

...possibly know where to get a A2620 schematic?

...possibly know where to find updated ROM images for the card (I think that is the least important - only if my ROMs should be defective; there are 390283-02 ROMs on it, but as I've kickstart 1.2 they should work and I don't plan to upgrade the motherboard beyond 1.3 for now).

...possibly know whether an upgrade of the motherboard ROMs to 1.3 might help? [I expect them to arrive from ebay].

Sorry for the long post, and I hope all things I write are correct. - Thank you for your reading time, and thank you for any of your kind feedback and any help in advance.

Kind regards, bubbleduck

Loedown · 07 May 2010, 03:59

Quote:

Originally Posted by blubbiduck

Apparently, the 68020 CPU never gets it's (locally on A2620 generated) -RESET pin changed to high logic level, so I think that CPU doesn't start running, but the 68000 in the motherboard keeps wating for it to go on.

A stuck reset pin is never going to allow the CPU to start, so you have a loop here, the B2000 is waiting and the card CPU is stuck. I looked through my schematics, I don't have the 2620.

It sounds like a logic state fault, similar to a bad gate, is it possible to send the card back for a refund, or if you let us know where you are in the world, we could recommend quite a few Amiga repair techs.

Philophus · 07 May 2010, 11:49

Dave Haynies site seems to be offline at the momentn there's usealy the specs you need on there.

http://www.thule.no/haynie/cpumods/a2620/docs/

zipper · 07 May 2010, 15:02

Use Wayback:
http://web.archive.org/web/*/http://...ds/a2620/docs/

Zetr0 · 07 May 2010, 15:25

@blubbiduck

hello there, welcome to EAB =)

it would seem you are fighting a bit of a battle with this legendary A2620 beast.

As you know there are some A2000 motherboards that need work arounds some of this is documented alas some is quite sketchy

I would like to point out its highly possible the A2620 Boot ROMS may be incompatible, there are some fixes around I shall have a lookie for some links.

Finally, pending on where you live, I have a Rev 4.5 A2000 motherboard that should be compatible with the A2620, its spare, so if you pay postage its yours (hit me up on PM).

I have just gone thorugh my schematics - alas I have the schema for A3630 but not A3620

I shall have a look around, good luck on your quest =)

rkauer · 09 May 2010, 23:54

IIRC, the 4.3 A2000 needs the on-board CPU removed when an accelerator is slotted in.

Don't know if this trick works in the ancient 1.2 ROM.

Jope · 10 May 2010, 08:47

This is only for the "short video slot" 4.x boards.

Hewitson · 10 May 2010, 10:15

Hmm why does it need to be removed? Design error, or something more?

alexh · 10 May 2010, 11:22

Pretty sure needing to remove the CPU was an A2000 thing. I don't remember having to remove the CPU on my B2000 with A2620 accelerator. The A2620 addendum manual describes a mechanism to fall back to 68000 mode and I dunno how that would be possible without the CPU fitted to the motherboard. Cannot hurt to try though.

Only issues I had were that I needed to update the A2620 ROM to use KS2.04 and above. Without the new ROM I got a green screen.

Recommend you try to update the ROM on your A2000 motherboard to KS1.3

[Update]It appears that A2620 works well with KS1.2

http://www.amiga.org/forums/showthread.php?t=48887

Sounds more and more like a dead board.

zipper · 10 May 2010, 15:50

Quote:

Originally Posted by alexh

Pretty sure needing to remove the CPU was an A2000 thing. I don't remember having to remove the CPU on my B2000 with A2620 accelerator. The A2620 addendum manual describes a mechanism to fall back to 68000 mode and I dunno how that would be possible without the CPU fitted to the motherboard. Cannot hurt to try though.

Naturally it doesn't work - the same situation is described in my Blizzard2060 manual - it can only be used in an early (German) A2000 when 68000 is pried out.

14 May 2010, 01:53

Hi all!

Thanks a lot for your replies! Here's a preliminary summary:

Short version:

Suspicion of defective PAL on my accelerator card further supported, A2620 schematics unavailable, all other recommended docs including PAL definition files previously reviewed. - I'll get additional hardware for testing but that will take a couple of weeks. Please don't hold your breath!

Detailed version:

I had reviewed a lot of information before my original post. The suggested former content from Dave Haynies site is now available at www.a68k.de/techwbhaupt.htm in a file a2620.zip; I had also looked up the disappeard www.thule... in archive.org and found both sources to have the same (helpful but too limited) content: These are PAL definition listings and some information on startup etc., but no complete schematic.

- Some means to read these PAL definitions is a software named WinCUPL and WinSIM available from a part supplier (sadly, only with exactly their parts in the library, but close enough). If you ever want to try that: It needs to be installed and run as admin (properly logged in, "run as" will not suffice) on modern systems. An installation attempt as normal user would fail when it should make registry entries and render the installed software (partially) and the installer (completely!!) unusable until extensive manual registry cleanup (on my XP). Running WinCUPL may need admin rights to access its device library. It also needs minimal adoptions in the PAL definition files: add a suitable device id in the header from the available device library, then it will roughly work. [...]

- The A2620 with v2 ROMs should work with A2000/B2000 kickstart 1.2 and 1.3, but v7 ROMs will be needed for kickstart 2.x and 3.x - most probably, because of the larger size of the newer ROMs that would otherwise overlap the old A2620 ROM, but possibly due to conflicting mouse button for startup menu usage.

- CPU removal should not be necessary on newer motherboards. It should be necessary only for the "old" "German" A2000 revision (before 4.x or so), because of some limitation in the bus arbitration (or DMA, I forgot) logic in the old board design. I found some detailed cpu extension slot pinout where slightly different pin assignments for A2000/B2000 were pointed out, and more detailed comments (though I don't now remember where). I had already tested my A2620 without the CPU installed, and with the respective jumper on the A2620 set ("use with old German 4-layer board"), but that had brought no improvement (as expected).

- Almost all mainboard A2000 (i.e. B2000) improvements from rev 4.1 to 6.x probably concerned issues unrelated with the A2620. Only one suggestion deals with cpu accelerators, and should improve stability when another card was installed in another extension slot (a [pullup- or so] resistor of 3.3 k pins 11..20 of IC U605 74LS245 or so). I tested with and without another card, and I also tested to temporarily put the resistor in - no change, so most probably not the cause of my problem. And after all, "improving stability" is slightly less than what I am currently looking for :-) :-) :-)

- No experience of yours has been reported on using the A2620 with 0 RAM installed so far. As far as I've found out, setting a jumper should prevent onboard memory from being configured at all, and the auto-configuration registers for the onboard memory should be independent from those of the remaining board, and become invisible to the system by setting that jumper. If I understand that correctly, this should make the idea of memory on the A2620 card completely disappear from the motherboard's mind, so it would surprise me if having no RAM chips installed would continue to trouble the system with that jumper installed. But still I don't know for sure (The PALs *might* specifically expect some memory IC output signal - but I can hardly imagine the rationale for such a design if not the 68020 CPU should rely on local memory for startup. But that would thoroughly reduce the flexibility of the design and would also have hindered the original development of the accelerator portion lest the memory portion were complete. A politician might do such a thing every day, but an engineer... probably not.)

- No feedback has been given on the additional / differently named jumpers on the A2620 vs. A2630 (for the A2630, docs & schematics would be available - but it is obviously different in some parts).

- An A2620 schematic is not readily available yet (I *might* try to trace back a manual for this card of which I've heard though.)

- PAL documentation is available (see above). I have tested some very basic functions of some of my PAL chips which are involved with -RESET and -BGACK etc., and found two outputs that would not be disabled (i.e. not put into tristate / high impedance / z state) as expected from the definition file. According to some of your feedback, "soft logic failure" was common in these boards, and according to some posting found elsewhere, "other components" would fail more often than the main processors on the board. All this supports my initial assessment that...:

-> No external condition (ROM version, motherboard revision, old CPU in socket, Jumpers etc.) does explain the bad behaviour of this board. Instead, it may have some logic failure, so that it doesn't remove the -RESET signal from its 68020 CPU though it should. The problem might be in its PALs, but details are as of yet unsure.

In the meantime, I got another A2000 on ebay; zetr0 has kindly offered me a rev 4.5 board (thanks!), and I may get another (defective) A2620. So I can try swapping parts to narrow down the problem.

But it will take several weeks before I can carry on the testing. If part swapping doesn't solve the puzzle, I might do a more detailed analysis (but that might take more time to happen). I'll report my findings...

In the meantime thank you again for your participation. It adds to my motivation to follow this up :-)

Greetings, blubbiduck.

PeterK · 14 May 2010, 06:12

I've just scanned my A2620 manual with the included schematics. It's about 65 MB in size and you can download it here:
http://www.alice-dsl.net/pkeunecke/A2620.rar
My good old A2000 is already dead for more than a year now since something has exploded inside (maybe a leaked battery or a bad capacitor ?). So, I cannot help you with any hardware details because I've no intentions to repair it or just to open the Amiga. It should rest in peace.

07 May 2010, 01:45	#1
blubbiduck Posts: n/a	Trying to get an A2620 to work, looking for experience/ideas/documentation/schematics Hello all. I'm new to Amiga, and new on this board and found several hints here already - thank you. Now, I've got a possibly defective A2620 marked 7-14-88 A/W 312831 REV 3 which I want to use in an Amiga 2000, board B2000 rev 4.1, kickstart 1.2 (but apparently with a MOS 8373 or so Gary? IC). The A2620 has 0 RAM installed, and the seller on ebay advertised it as producing a "green screen" on his A2000. In my system however, the card doesn't get that far. When it is plugged in, the monitor stays black on power up (with one slighly brighter line at the top of the screen). -- I don't have a keyboard yet, but a mouse - and pressing any combination of mouse buttons during/after bootup doesn't change a thing. The A2620 came wrapped in kind of thin plastic film that you'd use in the kitchen instead of usual electrostatic-protective-plastic-bags, so maybe it has been damaged on the way. I did some basic hardware testing: Apparently, the 68020 CPU never gets it's (locally on A2620 generated) -RESET pin changed to high logic level, so I think that CPU doesn't start running, but the 68000 in the motherboard keeps wating for it to go on. The 68881, however, has a reset signal that goes up shortly after powerup, just like the 68000 on the motherboard; both probably use the same signal. So I think the problem might most probaly lie in the PALs (maybe in handling bus arbitration between CPUs or A2620-local reset generation for 68020) (or in the ability of this card to run at all with my A2000). If I remove the MC68020, 68881, 68851, the ROMs, and all the PALs from the card - nevertheless, when it is plugged into the Amiga 2000, that one only shows a black screen upon power up. I tried many (maybe all) possible jumper configurations on the A2620. I've also confirmed that my motherboard bus slot has some rather plausible signals on all pins. The A2000 RTC battery was recently removed, with slightly discoloured areas on board seen, one pin of CPU slot showed blue stuff - that was cleaned, pin and neighbouring pins measured, should all still work. I've also confirmed that all ICs on the A2620 have correct power (both Vcc and GND), including the MC68xxx ICs. I can't see obviously defective leads on that board and I've successfully tested some doubtful lines to be ok. I've re-fixed a resistor on the back of the board that had been removed using photos in the WWW as a guide. All 74xx ICs on the A2620 seem to work (as far as I can check without removing/without using a logic analyzer). I also checked (only) the simple functions of (only) a few PALs coarsely: I found that some xxxxxx.OE signals may not work as I would expect from the .PLD files from Haynes. Specifically, the output of these lines is never disabled: U306 ABG.OE and U305 MEMSEL.OE. And maybe one or two input signals may work in the opposite polarity from what I expect: U305 !BOSS->TRISTATE, and !BEER/!BERR. But - that might all be unexpected function of the PALs, or my wrong interpretation of the .PLD files or of my findings :-), or the files at Haynes would describe other versions of the PALs though they match the numbers on the ICs). And I don't know by now whether a PAL can just lose its capability to disable its output and perform all other functionality quite as expected? Well - now I'm severely over my intended time budget, and a bit out of ideas (apart from firing up a logic analyzer which I will probably NOT do anytime soon for this board). However - before I put the card aside for a long time: Might anybody on this forum... ...have run the A2620 without 32-Bit-RAM installed (I set the appropriate Jumper to indicate zero RAM to be used on the board)? Is that possible at all? ...have run the A2620 in the B2000 rev 4.1 board? ...with that MOS Gary instead of the ...older...Toshiba?... ...have run the A2620 without a keyboard on the A2000? Might that stop it from booting?! ...possibly know where to get the A2620 manual properly describing the function of jumpers 202, 201 (or all jumpers)? [It has more, and differently named jumpers than the A2630, and I haven't found docs though I've searched extensively.] ...possibly know where to get a A2620 schematic? ...possibly know where to find updated ROM images for the card (I think that is the least important - only if my ROMs should be defective; there are 390283-02 ROMs on it, but as I've kickstart 1.2 they should work and I don't plan to upgrade the motherboard beyond 1.3 for now). ...possibly know whether an upgrade of the motherboard ROMs to 1.3 might help? [I expect them to arrive from ebay]. Sorry for the long post, and I hope all things I write are correct. - Thank you for your reading time, and thank you for any of your kind feedback and any help in advance. Kind regards, bubbleduck

10 May 2010, 11:22	#9
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,331	Pretty sure needing to remove the CPU was an A2000 thing. I don't remember having to remove the CPU on my B2000 with A2620 accelerator. The A2620 addendum manual describes a mechanism to fall back to 68000 mode and I dunno how that would be possible without the CPU fitted to the motherboard. Cannot hurt to try though. Only issues I had were that I needed to update the A2620 ROM to use KS2.04 and above. Without the new ROM I got a green screen. Recommend you try to update the ROM on your A2000 motherboard to KS1.3 [Update]It appears that A2620 works well with KS1.2 http://www.amiga.org/forums/showthread.php?t=48887 Sounds more and more like a dead board. Last edited by alexh; 10 May 2010 at 11:32.

14 May 2010, 01:53	#11
blubbiduck Posts: n/a	Trying to get an A2620 to work - preliminary summary of others' experience and docs Hi all! Thanks a lot for your replies! Here's a preliminary summary: Short version: Suspicion of defective PAL on my accelerator card further supported, A2620 schematics unavailable, all other recommended docs including PAL definition files previously reviewed. - I'll get additional hardware for testing but that will take a couple of weeks. Please don't hold your breath! Detailed version: I had reviewed a lot of information before my original post. The suggested former content from Dave Haynies site is now available at www.a68k.de/techwbhaupt.htm in a file a2620.zip; I had also looked up the disappeard www.thule... in archive.org and found both sources to have the same (helpful but too limited) content: These are PAL definition listings and some information on startup etc., but no complete schematic. - Some means to read these PAL definitions is a software named WinCUPL and WinSIM available from a part supplier (sadly, only with exactly their parts in the library, but close enough). If you ever want to try that: It needs to be installed and run as admin (properly logged in, "run as" will not suffice) on modern systems. An installation attempt as normal user would fail when it should make registry entries and render the installed software (partially) and the installer (completely!!) unusable until extensive manual registry cleanup (on my XP). Running WinCUPL may need admin rights to access its device library. It also needs minimal adoptions in the PAL definition files: add a suitable device id in the header from the available device library, then it will roughly work. [...] - The A2620 with v2 ROMs should work with A2000/B2000 kickstart 1.2 and 1.3, but v7 ROMs will be needed for kickstart 2.x and 3.x - most probably, because of the larger size of the newer ROMs that would otherwise overlap the old A2620 ROM, but possibly due to conflicting mouse button for startup menu usage. - CPU removal should not be necessary on newer motherboards. It should be necessary only for the "old" "German" A2000 revision (before 4.x or so), because of some limitation in the bus arbitration (or DMA, I forgot) logic in the old board design. I found some detailed cpu extension slot pinout where slightly different pin assignments for A2000/B2000 were pointed out, and more detailed comments (though I don't now remember where). I had already tested my A2620 without the CPU installed, and with the respective jumper on the A2620 set ("use with old German 4-layer board"), but that had brought no improvement (as expected). - Almost all mainboard A2000 (i.e. B2000) improvements from rev 4.1 to 6.x probably concerned issues unrelated with the A2620. Only one suggestion deals with cpu accelerators, and should improve stability when another card was installed in another extension slot (a [pullup- or so] resistor of 3.3 k pins 11..20 of IC U605 74LS245 or so). I tested with and without another card, and I also tested to temporarily put the resistor in - no change, so most probably not the cause of my problem. And after all, "improving stability" is slightly less than what I am currently looking for :-) :-) :-) - No experience of yours has been reported on using the A2620 with 0 RAM installed so far. As far as I've found out, setting a jumper should prevent onboard memory from being configured at all, and the auto-configuration registers for the onboard memory should be independent from those of the remaining board, and become invisible to the system by setting that jumper. If I understand that correctly, this should make the idea of memory on the A2620 card completely disappear from the motherboard's mind, so it would surprise me if having no RAM chips installed would continue to trouble the system with that jumper installed. But still I don't know for sure (The PALs might specifically expect some memory IC output signal - but I can hardly imagine the rationale for such a design if not the 68020 CPU should rely on local memory for startup. But that would thoroughly reduce the flexibility of the design and would also have hindered the original development of the accelerator portion lest the memory portion were complete. A politician might do such a thing every day, but an engineer... probably not.) - No feedback has been given on the additional / differently named jumpers on the A2620 vs. A2630 (for the A2630, docs & schematics would be available - but it is obviously different in some parts). - An A2620 schematic is not readily available yet (I might try to trace back a manual for this card of which I've heard though.) - PAL documentation is available (see above). I have tested some very basic functions of some of my PAL chips which are involved with -RESET and -BGACK etc., and found two outputs that would not be disabled (i.e. not put into tristate / high impedance / z state) as expected from the definition file. According to some of your feedback, "soft logic failure" was common in these boards, and according to some posting found elsewhere, "other components" would fail more often than the main processors on the board. All this supports my initial assessment that...: -> No external condition (ROM version, motherboard revision, old CPU in socket, Jumpers etc.) does explain the bad behaviour of this board. Instead, it may have some logic failure, so that it doesn't remove the -RESET signal from its 68020 CPU though it should. The problem might be in its PALs, but details are as of yet unsure. In the meantime, I got another A2000 on ebay; zetr0 has kindly offered me a rev 4.5 board (thanks!), and I may get another (defective) A2620. So I can try swapping parts to narrow down the problem. But it will take several weeks before I can carry on the testing. If part swapping doesn't solve the puzzle, I might do a more detailed analysis (but that might take more time to happen). I'll report my findings... In the meantime thank you again for your participation. It adds to my motivation to follow this up :-) Greetings, blubbiduck.

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07 May 2010, 11:49	#3
Philophus Registered User Join Date: Mar 2010 Location: Hampshire Posts: 151	Dave Haynies site seems to be offline at the momentn there's usealy the specs you need on there. http://www.thule.no/haynie/cpumods/a2620/docs/

07 May 2010, 15:02	#4
zipper Registered User Join Date: Mar 2004 Location: finland Posts: 1,837	Use Wayback: http://web.archive.org/web/*/http://...ds/a2620/docs/

07 May 2010, 15:25	#5
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	@blubbiduck hello there, welcome to EAB =) it would seem you are fighting a bit of a battle with this legendary A2620 beast. As you know there are some A2000 motherboards that need work arounds some of this is documented alas some is quite sketchy I would like to point out its highly possible the A2620 Boot ROMS may be incompatible, there are some fixes around I shall have a lookie for some links. Finally, pending on where you live, I have a Rev 4.5 A2000 motherboard that should be compatible with the A2620, its spare, so if you pay postage its yours (hit me up on PM). I have just gone thorugh my schematics - alas I have the schema for A3630 but not A3620 I shall have a look around, good luck on your quest =)

09 May 2010, 23:54	#6
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	IIRC, the 4.3 A2000 needs the on-board CPU removed when an accelerator is slotted in. Don't know if this trick works in the ancient 1.2 ROM.

10 May 2010, 08:47	#7
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	This is only for the "short video slot" 4.x boards.

10 May 2010, 10:15	#8
Hewitson Registered User Join Date: Feb 2007 Location: Melbourne, Australia Age: 41 Posts: 3,771	Hmm why does it need to be removed? Design error, or something more?

14 May 2010, 06:12	#12
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	I've just scanned my A2620 manual with the included schematics. It's about 65 MB in size and you can download it here: http://www.alice-dsl.net/pkeunecke/A2620.rar My good old A2000 is already dead for more than a year now since something has exploded inside (maybe a leaked battery or a bad capacitor ?). So, I cannot help you with any hardware details because I've no intentions to repair it or just to open the Amiga. It should rest in peace.

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