A3640 overclocking/upgrading

[protek]

You who have overclocked your A3640, have you just changed the crystal and made modifications to the timing lines, if necessary or have you also changed the actual CPU? Do you still need to apply the timing fixes even if you change the CPU with the crystal?

[Zetr0]

@Protek

the A3640 is a fickle beast and depending on the pcb revision, components onboard, age and cpu your milage will vary... but lets say the following.

1. you have a Rev 3.1 (quite common) A3640 Masked Board

2. Its advised that you replace the capcitors as they have been soldered the wrong way round, the PCB silk is actually printed incorrectly

3. You use a 33mhz capable 040 or faster.

4. you provide active cooling (that heatsink AND fan)

5. desolder the exsiting crystal and install a 14 pin dill socket.

--

recently I modified an A3640 with the timing fix, that allows for a faster crystal, also I installed a 40mhz CPU on the card. alas although it worked at 25 mhz, I never got to test it further than that as I had no crystals.

I then sold this to my friend MagerValp on AmiBay, he then took it up a bit more with a switch for the delay line, also change the capacitors too.

In the end he managed 33mhz stable from the card, wich is 7mhz Overclock... in perspective terms thats just under 33% frequency overclock and about a 30% performance increase.

Without trying to sound condescending, I was both please and proud of MagerValp's efforts on the A3640 =D

Now the thing is, this its not a garantee, some may overclock to 40mhz, (thats an 80mhz crystal) however some few dont even break 29mhz ( 58mhz) so if you do this, please be aware that it MAY NOT provide much of an increase.

Its all about how quick the "glue" & CPLD logic is at sampling (latching) the signals from the motherboard.

Now bare with me, I will get you pics and diagrams for your use =D

[Zetr0]

Modifed A3640@25 MHz (Click for larger images)



In this pic you see the upgraded heatsink and Fan combination, under this is a FULL CORE (MMU & FPU) 040 rated for 40mhz



The unit has had the Timing Line modification (in Commodore Blue 30 Awg)



Also soldered Turned (gold plated) socket pins for changing of the Oscilator (crystal)





In great working condition



now getting the Cap replacement list and Delay Line mod instructions

[protek]

@ Zetr0:
Thanks for the insight to the anatomy of the 3640. Mine's a rev 3.0 with cap change done.

[alexh]

You really need to find a MC68040RCxx which has the L88M or K63H mask sets as they run almost cold at 40MHz even without a heatsink & fan.

[Zetr0]

heres the Delay Line Fix

[Anemos]

Zetr0 guru hardware

[protek]

Originally Posted by Anemos

Zetr0 guru hardware

I concur.

[alexh]

Nice clarification, with much clearer pictures of a pre-existing mod

http://members.iinet.net.au/~davem2/...ock/a3640.html

[Zetr0]

Originally Posted by Anemos

Zetr0 guru hardware

Originally Posted by protek

I concur.

truely... I am humbled.... its a good thing the wifes not here or she would see me blushing like a girl....

to be fair there are many way better than I, I just bring good looks to the party

Originally Posted by alexh

Nice clarification, with much clearer pictures of a pre-existing mod

http://members.iinet.net.au/~davem2/overclock/a3640.html

LOL., i was frantically searching for this in my links... I couldn't find it, hence I posted up the AmiBay Pics!!!

thanks for the Link Alexh the thread is all nice and round now =)

[MagerValp]

It should be noted that overclocking the A3640 also means overclocking the motherboard SIMMs. It's likely that the SIMMs will become unstable before the 040 does. The upshot is that you get a sorely needed boost in RAM performance.

[Zetr0]

@MagerVap

Its doesn't *overclock* perse' it just hammers the rams a bit harder (30% in the case of a 66mhz Osc on the A3640), the frequency is still the same as this is governed by the motherboard clock.

I will have to check but I do beleive its 28mhz.

However you are most correct in saying my friend that the memory is likely to give out (in the sense of keeping up and not in the sense of blowing up or damaging) before the A3640 lol!

@thread

A thought would be that you could change the RAM to 60 or 50ns, this might give you a little extra milage, although I do believe the real culprit of limit will be the latching logic that decodes / address the rams themselfs.

still worth it though =D

[MagerValp]

Originally Posted by Zetr0

Its doesn't *overclock* perse' it just hammers the rams a bit harder (30% in the case of a 66mhz Osc on the A3640), the frequency is still the same as this is governed by the motherboard clock.

Sure, since regular DRAM isn't clocked, it simply has a certain access latency, but the effect is the same.

A thought would be that you could change the RAM to 60 or 50ns, this might give you a little extra milage, although I do believe the real culprit of limit will be the latching logic that decodes / address the rams themselfs.

I tried unplugging everything but the chip ram SIMM, but still couldn't get it to boot at 40 MHz. Unfortunately I don't have any fast SIMMs lying around, and no oscillators for testing 35 and 37.5 MHz, but 33 MHz is likely not the limit.

[cosmicfrog]

thread necromancy

I now own the A3640 from Post 3 my question is How is the heat sink held on ?? is it gum, glue or wishful thinking hehehehehe

I want to replace the fan/heatsink as the one in the picture did`t last long, bloody thin wires and no surround for the fan..

[rkauer]

You can glue the heatsink using a thermal pad, or even better: some artic silver paste in the middle of the CPU and then two little drops of superglue on two non-adjacent corners.

[Zetr0]

@cosmi

my friend the heat-sink is infact 4 smaller sinks with thermal glue based grip-pads - thanks to our friends at 3M =)

Basically the hotter the CPU gets the more the glue-pads bond and the better the heat effciency. You should be able to pry them off the CPU it might be a little difficult though.

The Fan that is on there sucks down so there is no need for a shroud, infact the shoud will probably buffet air and have a mild loss in performance - at the moment it creates a wide vortex - you could make your own with some small pastic strips or even plasticard =)

[joeksterz]

I have had fairly good luck with my a3640 overclocking attempts. My rev 3.0 runs stable at 36mhz, but will not even post at 40mhz. I am using a 40mhz 040 and 60ns ram that can run in "Ramsey skip mode" at 25mhz - 36mhz requires normal memory timings. The delay line made all the difference since without it, I was not so stable at 30mhz.

[Zetr0]

the biggest limmitation on the A3640 is the speed of the GAL's CPLD's on the board

Its bascially their latching and propagation time that goverens the end result - if one could find faster GAL's there exists the possibility of a safe 40mhz

I will say that its not just a case of finding a faster (in propagation and latching) 5v pin compatible CPLD - you will need to do some math in timings to make sure you dont out-latch the CPU or the Bus.

[cosmicfrog]

great I`ll attempt to pry away the heatsinks

the fan has long gone it had an argument with the ide lead and lost hehehhehe

[Cosmos]

>the biggest limmitation on the A3640 is the speed of the GAL's CPLD's on the board

All GAL22V10 are 5ns on my A3640 now
All GAL16V8 are 7ns now

But still 30.5 Mhz... No boot at 32 Mhz...


Some 74 need to be updated by faster ones ?

[stachu100]

Despite technical challenge: Is your efforts all worth to have 10MHz more from this card?

I agree that it's a good lesson, but from practical point of view there is no big difference. Also all this overclocking doesn't look well from financial point of view.
It's better to spent 10-20EUR more and buy 40MHz version in my opinion.

[Cosmos]

>from practical point of view there is no big difference

lol !

Big diff from 25 to 33 with a 040... And from 25 to 40, it's !

[Don_Adan]

Originally Posted by Cosmos

>from practical point of view there is no big difference

lol !

Big diff from 25 to 33 with a 040... And from 25 to 40, it's !

If you are good enough, better make Quaddoubler for your A3640 board and perhaps you can reach 50 MHz speed for MC68040 CPU. Here is the link to homemade Quaddoubler:
http://www.nextcomputers.org/forums/viewtopic.php?t=56

[SpeedGeek]

Been There Done That! You don't need faster PAL's or GAL's. Everyone has overlooked the clock speed limitations of your A3000 or A4000 motherboard. The solution is to run your motherboard with a synchronized 20 Mhz clock but you will need a few cut an jumper modifications. The following results are from my A3640 @40Mhz + 68030 state machine modifications + ramsey 4 clock cycle @20Mhz. AIBBLogFile*********************************************************************************** System Static Data ----------------------------------------------------------------------------- System CPU: 68040 System FPU: 68040 System MMU: 68040 CPU Clock Rate: 40.0 MHz FPU Clock Rate: 40.0 MHz Operating System Version: 40.68 ( 3.x ) ======================= System Memory Information ============================ NODE #1 Node Name: expansion memory Node Size: 16.00 MBytes Bus Port Size: 32 Bit Address Range: $07000000--$08000000 Node Priority: 30 ----------------------------------------------------------------------------- NODE #2 Node Name: chip memory Node Size: 2.00 MBytes Bus Port Size: 32 Bit Address Range: $00001000--$00200000 Node Priority: -10 ----------------------------------------------------------------------------- ***************************************************************************** ========================== Test Information Section ========================== Test Name: InstTest Parameters: Not applicable to this test. Multitasking: DISABLED Test Code Location: Memory Node #1 Test Data Location: Memory Node #1 Test Result: 7810894.89 Instructions/Second (Higher = Better Performance) ============================ Comparison Ratings ============================= This Machine : 16.94 A600-NF : 1.00 (68000 | SC Math) Base System A1200-NF : 1.75 (68020 | SC Math) A3000-25 : 5.47 (68020 | CP Math) A4000-40 : 10.05 (68020 | 40 Math) --------------- System Dynamic Information for this test ------------------- Instruction Cache: ENABLED Data Cache: ENABLED Inst Cache Burst Mode: -------- Data Cache Burst Mode: -------- Data Cache Write Allocate: -------- 68040 Copyback Mode: ENABLED ----------------------------------------------------------------------------- System Supervisor Stack Address: $07000AC0 AIBB Process Stack Address: $07218C0C Operating System Memory Location: $07FFBD00 Current OS Dispatch Quantum: 4 ***************************************************************************** END OF LOG FILE

[bebek]

Originally Posted by SpeedGeek

Been There Done That! You don't need faster PAL's or GAL's. Everyone has overlooked the clock speed limitations of your A3000 or A4000 motherboard. The solution is to run your motherboard with a synchronized 20 Mhz clock but you will need a few cut an jumper modifications and a 74F74 to divide the clock on a A4000. The following results are from my A3640 @40Mhz + 68030 state machine modifications + ramsey 4 clock cycle @20Mhz. AIBBLogFile *********************************************************************************** System Static Data ----------------------------------------------------------------------------- System CPU: 68040 System FPU: 68040 System MMU: 68040 CPU Clock Rate: 40.0 MHz FPU Clock Rate: 40.0 MHz Operating System Version: 40.68 ( 3.x ) ======================= System Memory Information ============================ NODE #1 Node Name: expansion memory Node Size: 16.00 MBytes Bus Port Size: 32 Bit Address Range: $07000000--$08000000 Node Priority: 30 ----------------------------------------------------------------------------- NODE #2 Node Name: chip memory Node Size: 2.00 MBytes Bus Port Size: 32 Bit Address Range: $00001000--$00200000 Node Priority: -10 ----------------------------------------------------------------------------- ***************************************************************************** ========================== Test Information Section ========================== Test Name: InstTest Parameters: Not applicable to this test. Multitasking: DISABLED Test Code Location: Memory Node #1 Test Data Location: Memory Node #1 Test Result: 7810894.89 Instructions/Second (Higher = Better Performance) ============================ Comparison Ratings ============================= This Machine : 16.94 A600-NF : 1.00 (68000 | SC Math) Base System A1200-NF : 1.75 (68020 | SC Math) A3000-25 : 5.47 (68020 | CP Math) A4000-40 : 10.05 (68020 | 40 Math) --------------- System Dynamic Information for this test ------------------- Instruction Cache: ENABLED Data Cache: ENABLED Inst Cache Burst Mode: -------- Data Cache Burst Mode: -------- Data Cache Write Allocate: -------- 68040 Copyback Mode: ENABLED ----------------------------------------------------------------------------- System Supervisor Stack Address: $07000AC0 AIBB Process Stack Address: $07218C0C Operating System Memory Location: $07FFBD00 Current OS Dispatch Quantum: 4 ***************************************************************************** END OF LOG FILE

I have tried standard mod yesterday and able to achieve 33MHz for a minute and then yellow screen . Can you show us the way please ? A small diagram ? Where from is this synchronised 20MHz ?

[Loedown]

Originally Posted by SpeedGeek

On the A3000 the syncronized 20Mhz clock is obtained by disconnecting the 50 Mhz oscillator and connecting the 40 Mhz clock from the A3640 delay line to the A3000 74F74 input (R121). The 10 ns tap works good for me. You also need to disconnect the 40 Mhz clock from pin 1 of U208 on the A3640 and connect the 20 Mhz clock. Pin 1 of the A3000 delay line worked good for me. All motherboard jumpers should be set to "Internal" and "16 Mhz". Also, you need to disconnect the A3640 cpu clock and clock 90 from R102 & R101 on the A3640. On the A4000 you need to get a 74F74 IC and configure it as a standard clock divider. You could crop pins 1-6 and 8-13 and then solder it directly on top of the A3640 delay line. Disconnect cpu clock and clock 90 from the delay line. Connect the 74F74 inputs to the A3640 delay line (15 and 25 ns taps*) and the 74F74 outputs to R102 and R101 on the A3640. Remember to do the U208 clock modification described above. Do you still need a diagram? (* = an educated guess). Good Luck!

On the A3000 the syncronized 20Mhz clock is obtained by disconnecting the 50 Mhz oscillator and connecting the 40 Mhz clock from the A3640 delay line to the A3000 74F74 input (R121). The 10 ns tap works good for me. You also need to disconnect the 40 Mhz clock from pin 1 of U208 on the A3640 and connect the 20 Mhz clock. Pin 1 of the A3000 delay line worked good for me. All motherboard jumpers should be set to "Internal" and "16 Mhz". Also, you need to disconnect the A3640 cpu clock and clock 90 from R102 & R101 on the A3640. On the A4000 you need to get a 74F74 IC and configure it as a standard clock divider. You could crop pins 1-6 and 8-13 and then solder it directly on top of the A3640 delay line. Disconnect cpu clock and clock 90 from the delay line. Connect the 74F74 inputs to the A3640 delay line (15 and 25 ns taps*) and the 74F74 outputs to R102 and R101 on the A3640. Remember to do the U208 clock modification described above. Do you still need a diagram? (* = an educated guess). Good Luck!

Pics or it never happened

[SpeedGeek]

On the A3000 the syncronized 20Mhz clock is obtained by disconnecting the 50 Mhz oscillator and connecting the 40 Mhz clock from the A3640 delay line to the A3000 74F74 input (R120). The 10 ns tap works good for me. There are 2 optional mods to U208 on the A3640 needed for Ramsey to run a 4 clock cycle. All motherboard jumpers should be set to "Internal" and "16 Mhz". Also, you need to disconnect the A3640 cpu clock and clock 90 from R102 & R101 on the A3640.

On the A4000 you have the 74F74 and delay line available at different locations (see A4000 schematics) than the A3000. A diagram is provided. Good Luck! PS. You can use 1 or 2 unused pins on the 200 pin cpu connector to connect the jumper(s) to the A3640 so you can remove the A3640 without unsoldering jumper wires.

** NEWS UPDATE ** I have added as a second option another way to do the U208 part of the mod. It eliminates the possible problem with U208 timing from the motherboard delay line and 1 of the motherboard jumpers to the A3640. The only trick is finding the trace to pin 9.

http://www.amibay.com/showthread.php?t=19993

[SpeedGeek]

Disregard my previous instructions to add a 74F74 to the A3640 delay line on the A4000. The same clock divider and delay line circuitry are available (at different locations) on the A4000 motherboard. So you should have no difficulty adapting this mod to the A4000. Silly me, I should have checked the A4000 schematics before I made the above post.

[SpeedGeek]

** NEWS UPDATE ** The 74Fx803 clock divider on the A3640 is rated to run at 70 Mhz max! Obviously, your mileage will vary. If you have tried TIMING ADJUSTMENTS ON BOTH DELAY LINES* and are still having problems with this mod try an oscillator in the range of 66 to 74 Mhz and adjust the timing on either delay line. If your 74Fx803 won't run reliably at 80 Mhz you have the options of using a different chip (74F74) or even a clock doubler chip if you really want to get to 40 Mhz. *Your timing @40 Mhz should be within +-5 ns of mine. Otherwise try to reconnect U208 Pin 1 to the cut trace. This part of the mod is only needed for Ramsey to run a 4 clock cycle. Unfortunately, it's also the most timing critical part.

** 2ND NEWS UPDATE **
A datasheet has been uploaded. It would be a good idea to make sure the +5 Volt supply to the A3640 is at least 5 Volts. Another potential problem is skew between Bclk and Pclk. Motorola specifies 9 ns @25 Mhz and gives no spec. @ 40 Mhz. Using the formula 25/40 x 9 gives a calculated value of 5.6 ns. With the 74Fx803 being overclocked it's likely to be right on the edge. A skew problem could easily mislead you to believe your 74Fx803 or 68040 won't run at the desired clock speed! Fortunately, there is a simple cut and jumper mod to compensate for the skew.

http://www.amibay.com/showthread.php?t=19993

[zipper]

And all this effort strangled by the slow mobo memory...

[stachu100]

I share your point. As A3640 overclocking from 25MHz to 33MHz is quite easy (10 min of work) and can be justified, but I don't understand the people spending a lot of efforts and money just to get few MHz more and all this effort will be destroyed by slow FAST memory anyway.
Much better is to buy card like WarpEngine 4040 with onboard FAST (much faster than FAST on A4000 mobo) and SCSI for about 100EUR more than A3640.

It seems that I don't understand a lot of things...

[zipper]

I think a big part of overclocking benefits when going over 28 MHz is lost on wait states.

[Cosmos]

68040 have 8 Ko of cache !

[SpeedGeek]

The following Bustest results (cpu nodatacache) are from Ramsey 4 clock cycle @20 Mhz (380 clock refresh):
5.System3.9:> bustest fast
BusSpeedTest 0.19 (mlelstv) Buffer: 262144 Bytes, Alignment: 32768
========================================================================
memtype addr op cycle calib bandwidth
fast $07F38000 readw 205.6 ns normal 9.7 * 10^6 byte/s
fast $07F38000 readl 196.6 ns normal 20.3 * 10^6 byte/s
fast $07F38000 readm 210.7 ns normal 19.0 * 10^6 byte/s
fast $07F38000 writew 205.5 ns normal 9.7 * 10^6 byte/s
fast $07F38000 writel 204.9 ns normal 19.5 * 10^6 byte/s
fast $07F38000 writem 196.3 ns normal 20.4 * 10^6 byte/s

Not quite as fast as WarpEngine memory but a significant improvement. The only problem is you need a universal programmer to do the state machine mod.

** UPDATE July 23, 2011 **

ROM Bustest results with Fat Gary @40 Mhz have been removed since Fat Gary was not always reliable at this clock speed.

[SpeedGeek]

The original posts were updated to address possible problems with overclocking the A3640 which the motherboard 1/2 clock mod doesn't solve. Hopefully, you now have some good ideas work through any such problems.

Secondly, for those who say "It's not worth the effort or expense" I have the following comments:
You never know how much faster your system can go unless you actually try to make it faster!

I successfully overclocked my 25 Mhz MC68040 to 40 Mhz! The cost of a socket and an oscillator was a minimal expense. I recycled a cooling fan from a discarded 486 motherboard.

Some users have already purchased a 33 or 40 Mhz 040 and a cooling fan just to do the Clock 90 mod. So why discourage them from trying to get the most from their investment?

I understand the few A3640 owners who got 35-37 Mhz with the Clock 90 mod may decide it's not worth the effort to get a few more Mhz.

However, this mod could be used by A4000 owners who have 80 ns fast memory to get to 40 Mhz!. It could also be used by A3000 owners who are limited by SuperDMAC to around 30 Mhz regardless of their fast memory speed.

PS. A3000T and DMAC 04 users please let me know if you could overclock your motherboard past 30 Mhz. Thanks.

http://www.amibay.com/showthread.php?t=19993

[SpeedGeek]

A3640 @ 50Mhz! Been there. Done that!
Who would have guessed a MC68040RC25 would go that far?

AIBB benchmarks are with 68030 state machine mod + Ramsey 5 clock cycle @ 25Mhz (380 clock refresh). Also, here are my (CPU nodatacache) Bustest results:

BusSpeedTest 0.19 (mlelstv) Buffer: 262144 Bytes, Alignment: 32768
========================================================================
memtype addr op cycle calib bandwidth
fast $07030000 readw 204.4 ns normal 9.8 * 10^6 byte/s
fast $07030000 readl 204.8 ns normal 19.5 * 10^6 byte/s
fast $07030000 readm 210.1 ns normal 19.0 * 10^6 byte/s
fast $07030000 writew 204.6 ns normal 9.8 * 10^6 byte/s
fast $07030000 writel 205.2 ns normal 19.5 * 10^6 byte/s
fast $07030000 writem 204.6 ns normal 19.5 * 10^6 byte/s

BusSpeedTest 0.19 (mlelstv) Buffer: 262144 Bytes, Alignment: 32768
========================================================================
memtype addr op cycle calib bandwidth
rom $00F80000 readw 251.7 ns normal 7.9 * 10^6 byte/s
rom $00F80000 readl 251.1 ns normal 15.9 * 10^6 byte/s
rom $00F80000 readm 246.8 ns normal 16.2 * 10^6 byte/s

P.S. Don't even think about trying this with out 68030 state machine mod and a clock doubler circuit or something faster than the 74Fx803 if you prefer clock dividers.

http://www.amibay.com/showthread.php?t=19993

[rkauer]

Me needs to uprate my A3000!

@Speedgeek: you used the latest L88M 040 mask or any MC68040 will do?

[SpeedGeek]

@rkauer
I don't know what the mask set is but it's probably the first or second mask set of the MC68040. My A3640 is a rev3.2 so it's probably one of the last boards made by C= in early 1994.

[rkauer]

My A3640 is upgraded to 3.2 (was 3.1 but I swapped the U209 chip) and it have a MC68040.

I think I'll do a thorough search in all your instructions to uprate my A3000.

[SpeedGeek]

** 68030 STATE MACHINE MOD RELEASED! **
I've decided to release the 68030 state machine mod as it is since it's unlikely that any more changes will be made from this point on. For those of you who have not been following the Amibay A3640 upgrade thread this a completely seperate mod from the other mods previously posted here on EAB. However, it most certainly is related to the many benchmark results I have posted here. Enjoy!

http://www.amibay.com/showthread.php?t=19993