A3640 cap replacement and overclocking

MagerValp · 05 September 2009, 23:20

I bought an A3640 prepared for overclocking from Zetr0 on AmiBay a few weeks ago. He hadn't actually tested it at anything other than 25 MHz, so first up was buying a 66 MHz oscillator. The card booted alright, but froze after a short while due to heat, so next up was adding a fan connector to the A4000. The card also has three 22 µF caps mounted backwards, and as you can see in the pics they were leaking electrolyte. Fortunately there wasn't any damage done to the board. With fresh caps and the fan connected, the machine has been running nicely for several hours now. SysInfo and AIBB shows a significant speed boost, even though SysInfo somehow gets the clock speed totally wrong.

If you have an A3640 in your A4000, replacing the caps and doing the delay line mod is a few minutes of work, and costs less than €10 - go for it!

alexh · 05 September 2009, 23:36

Nice, I have a few v3.0's in a box I've been meaning to cut-n-jumper & update the PLD's to make them v3.2. Might as well do this while I am at it.

Just a shame the A3640 sucks as an accelerator. No fast RAM and no burst mode

Very cheap though.

MagerValp · 06 September 2009, 09:09

While the memory interface on the A3640 undoubtedly sucks, I think people are overestimating the impact it has. Take a peek at the AIBB results here:

http://amiga.resource.cx/perf/aibbde.html

The X-Calibur quadruples the memory bandwidth, yet the speedup on the other integer tests only increases by an average of 33%. Likewise the 28 MHz WarpEngine only gets a 47% speedup. Compare this to overclocking the A3640, which gets a 33% speedup across the board.

Naturally some applications are more sensitive to memory bandwidth than others, but for most apps an overclocked A3640 is excellent bang per buck.

Zetr0 · 06 September 2009, 12:45

Some nice work MagerValp =)

technically speaking though, that 040 is *underclocked* its a 40mhz component

+)

MagerValp · 06 September 2009, 15:57

True, the CPU is, but the board itself is quite clearly designed for 25 MHz, and nothing else. Since it appears to scale up memory access speed together with the CPU, that's probably where the limit is. I wish I had some 50 ns SIMMs to test with...

alexh · 06 September 2009, 16:20

Quote:

Originally Posted by MagerValp

I wish I had some 50 ns SIMMs to test with...

http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=160127919628

rkauer · 06 September 2009, 17:34

The A3640 can be "overclocked" further than just 33MHz (not much more).

Psst!

NOTE: using this hack you will able to use even 80MHz crystal (40MHz on the 040!), but this depends on experimentation.

alexh · 06 September 2009, 17:42

Erm, what do you think Zetro did to it when he made it "prepared for overclocking"?

He followed that guide!

MagerValp · 06 September 2009, 18:28

Quote:

Originally Posted by rkauer

The A3640 can be "overclocked" further than just 33MHz (not much more).

Psst!

NOTE: using this hack you will able to use even 80MHz crystal (40MHz on the 040!), but this depends on experimentation.

My Amiga doesn't even boot with an 80 MHz crystal, with or without the delay line hack.

rkauer · 06 September 2009, 21:16

Quote:

Originally Posted by alexh

Erm, what do you think Zetro did to it when he made it "prepared for overclocking"?

He followed that guide!

I know that, Alexh.

I pointed the page to show the possibilities of the card.

If it refuses to work @40MHz, them try a 74MHz crystal (37MHz on the 040). No damage will be made to the Amiga or the accelerator.

source · 06 September 2009, 22:10

I have very little electronic knowledge, so this may be a basic question, but if these capacitors have a tendency to leak and cause significant damage to the motherboard, can an other style of capacitors be used that don't leak. (Or do all capacitors contain the compounds that destroy the traces). The other quesiton I have is can you remove the capacitors that normally degrade and have them relocated onto a breadboard with ribbon cable running to the breadboard, so that if the capacetors leak again, the damage would be isolated to a very cheap component that can be replaced quite easily.

rkauer · 07 September 2009, 02:47

The capacitor fluid is slightly acid. The most common damage it causes is on the glue who holds the copper traces to the board.

There is one type of electrolytic capacitor that don't leak: tantalum units. They are more expensive (not the quantity used have a huge impact on final price). They don't leak, but can explode if abused (high temperature, wrong insertion polarity or too high frequency).

Regular capacitors are not prone to leak, just those made on the Amiga era are. Replace them with high quality units and don't worry.

A good advice is washing the entire affected boards with pure water on a dishwasher set to ecological cycle and let the board dry in a ventilated area for at least 2 entire days.

source · 07 September 2009, 04:25

Capacitors that are beginning to fail (bulging). Do they bulge only at the top of the capacitor or do they bulge from the sides. The reason why I ask is that I am currently attempting to refresh all my amigas I have just taken my A2000 apart and cleaned the board from dust. Before I put it back together, I would like to make sure that the capacitors are good. Once the 2000 is back up and running, then I will work on my amiga 3x4000.

MagerValp · 07 September 2009, 08:13

Quote:

Originally Posted by rkauer

I If it refuses to work @40MHz, them try a 74MHz crystal (37MHz on the 040).

I would if I could find one. No luck at Mouser, ELFA, or Conrad, and Farnell doesn't sell to hobbyists...

I'd ideally like to get 70, 72, and 75 MHz crystals, but they seem to be rare.

rkauer · 08 September 2009, 02:06

Did you try Futurlec in UK? They sell those babies.

[EDIT] No, they not sell those any more...

rkauer · 08 September 2009, 02:51

After some searching, I found a producer of the units ( http://www.oakind.com/products/xo/vpa1.htm ), but not a vendor...

papa_november · 08 September 2009, 02:58

Quote:

Originally Posted by source

Capacitors that are beginning to fail (bulging). Do they bulge only at the top of the capacitor or do they bulge from the sides. The reason why I ask is that I am currently attempting to refresh all my amigas I have just taken my A2000 apart and cleaned the board from dust. Before I put it back together, I would like to make sure that the capacitors are good. Once the 2000 is back up and running, then I will work on my amiga 3x4000.

In my experience, SMT capacitors give almost no indication that they're about to fail. They look just fine until they gradually start leaking.

05 September 2009, 23:20	#1
MagerValp Registered User Join Date: Aug 2008 Location: Göteborg / Sweden Posts: 237	A3640 cap replacement and overclocking I bought an A3640 prepared for overclocking from Zetr0 on AmiBay a few weeks ago. He hadn't actually tested it at anything other than 25 MHz, so first up was buying a 66 MHz oscillator. The card booted alright, but froze after a short while due to heat, so next up was adding a fan connector to the A4000. The card also has three 22 µF caps mounted backwards, and as you can see in the pics they were leaking electrolyte. Fortunately there wasn't any damage done to the board. With fresh caps and the fan connected, the machine has been running nicely for several hours now. SysInfo and AIBB shows a significant speed boost, even though SysInfo somehow gets the clock speed totally wrong. If you have an A3640 in your A4000, replacing the caps and doing the delay line mod is a few minutes of work, and costs less than €10 - go for it! Attached Thumbnails Last edited by MagerValp; 06 September 2009 at 16:16. Reason: spelling & grammar

08 September 2009, 02:06	#15
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	Did you try Futurlec in UK? They sell those babies. [EDIT] No, they not sell those any more... Last edited by rkauer; 08 September 2009 at 02:21.

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05 September 2009, 23:36	#2
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,331	Nice, I have a few v3.0's in a box I've been meaning to cut-n-jumper & update the PLD's to make them v3.2. Might as well do this while I am at it. Just a shame the A3640 sucks as an accelerator. No fast RAM and no burst mode Very cheap though.

06 September 2009, 09:09	#3
MagerValp Registered User Join Date: Aug 2008 Location: Göteborg / Sweden Posts: 237	While the memory interface on the A3640 undoubtedly sucks, I think people are overestimating the impact it has. Take a peek at the AIBB results here: http://amiga.resource.cx/perf/aibbde.html The X-Calibur quadruples the memory bandwidth, yet the speedup on the other integer tests only increases by an average of 33%. Likewise the 28 MHz WarpEngine only gets a 47% speedup. Compare this to overclocking the A3640, which gets a 33% speedup across the board. Naturally some applications are more sensitive to memory bandwidth than others, but for most apps an overclocked A3640 is excellent bang per buck.

06 September 2009, 12:45	#4
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	Some nice work MagerValp =) technically speaking though, that 040 is underclocked its a 40mhz component +)

06 September 2009, 15:57	#5
MagerValp Registered User Join Date: Aug 2008 Location: Göteborg / Sweden Posts: 237	True, the CPU is, but the board itself is quite clearly designed for 25 MHz, and nothing else. Since it appears to scale up memory access speed together with the CPU, that's probably where the limit is. I wish I had some 50 ns SIMMs to test with...

06 September 2009, 17:34	#7
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	The A3640 can be "overclocked" further than just 33MHz (not much more). Psst! NOTE: using this hack you will able to use even 80MHz crystal (40MHz on the 040!), but this depends on experimentation.

06 September 2009, 17:42	#8
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,331	Erm, what do you think Zetro did to it when he made it "prepared for overclocking"? He followed that guide!

06 September 2009, 22:10	#11
source Zone Friend Join Date: Jul 2005 Location: Toronto, Canada Posts: 734	I have very little electronic knowledge, so this may be a basic question, but if these capacitors have a tendency to leak and cause significant damage to the motherboard, can an other style of capacitors be used that don't leak. (Or do all capacitors contain the compounds that destroy the traces). The other quesiton I have is can you remove the capacitors that normally degrade and have them relocated onto a breadboard with ribbon cable running to the breadboard, so that if the capacetors leak again, the damage would be isolated to a very cheap component that can be replaced quite easily.

07 September 2009, 02:47	#12
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	The capacitor fluid is slightly acid. The most common damage it causes is on the glue who holds the copper traces to the board. There is one type of electrolytic capacitor that don't leak: tantalum units. They are more expensive (not the quantity used have a huge impact on final price). They don't leak, but can explode if abused (high temperature, wrong insertion polarity or too high frequency). Regular capacitors are not prone to leak, just those made on the Amiga era are. Replace them with high quality units and don't worry. A good advice is washing the entire affected boards with pure water on a dishwasher set to ecological cycle and let the board dry in a ventilated area for at least 2 entire days.

07 September 2009, 04:25	#13
source Zone Friend Join Date: Jul 2005 Location: Toronto, Canada Posts: 734	Capacitors that are beginning to fail (bulging). Do they bulge only at the top of the capacitor or do they bulge from the sides. The reason why I ask is that I am currently attempting to refresh all my amigas I have just taken my A2000 apart and cleaned the board from dust. Before I put it back together, I would like to make sure that the capacitors are good. Once the 2000 is back up and running, then I will work on my amiga 3x4000.

08 September 2009, 02:51	#16
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	After some searching, I found a producer of the units ( http://www.oakind.com/products/xo/vpa1.htm ), but not a vendor...

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