A3640 @ 50Mhz!

[SpeedGeek]

** NEWS UPDATE **

A NEW 50 MHz schematic was recently uploaded to post #1. It utilizes the motherboard logic to provide the 25 MHz clocks. Both clock jumpers are set to INTERNAL and 25 MHz. Also, the clock doubler GAL must be programmed with the .jed file provided. Note: The A4000 may need an additional jumper to connect CPUCLK to the CPU slot connector with this configuration. If this is to complicated for you, then consider apollo630's clock doubling method which uses the A3640 logic to provide the 25 MHz clocks. It is very well documented on this thread:

http://eab.abime.net/showthread.php?t=63160

Also, there are several optional (but recommended) A3640 resistor load fixes as well: R402 - R404 change to 2.2K, RP400 - RP405 change to 3.3K.

Note2: There several other undocumented mods I made to my A3000 to stabilize and reduce power consumption, improve cooling, resistor load fixes, etc. Also, since there are significant differences between A3000 and A4000 motherboards, XC vs. MC 68040's and 3 different A3640 revisions it's just NOT practical to make a simple step by step guide which works for everyone.

P.S. A VERY SPECIAL THANKS to apollo630 for testing the new U207 and U208 I made to save some lame hackers a few cut and jumper mods!

 

[apollo630]

Update: RAMSEY-07 & DMAC-02 in A3000

After finishing SpeedGeeks state machine mod for my A3640 I was looking for ways to further accelerate fastmem access time. Since I do only have 80ns static-column mode RAM I started playing around with page mode. But RAMSEY-04 is not really supporting page mode: when turning on page mode with RAMSEY-04 SCSI was not working anymore. RAMSEY-07 is supporting page mode but unfortunately it is told to not work together with DMAC-02. RAMSEY-07 is only working with DMAC-04 which is impossible to get.

Now I've got the chance to buy a RAMSEY-07 and so decided to just give it a try with DMAC-02 and it was working for both the build-in 68030 as well as the A3640! Yet, I don't know why! SpeedGeek, is it possible that your state machine mod is helping?

So with page mode turned on I am now saving another 2 cycles for fastmem accesses to the same page. This in conjunction with the 2 cycle saving from SpeedGeeks state machine mod is now allowing to finish fastmem reads to the same page in only 4 cycles (160ns) using 80ns static-column RAM and still have SCSI working!

Configuration:

* A3000 desktop rev 9/01
* 16MB 80ns static-column fast ram
* RAMSEY-07 (390541-07 / 45-RAMSEY)
* DMAC-02 (390537-02 / 81-SUPER DMAC)
* WD33C93A-PL 00-04

-- Jens

 

[SpeedGeek]

** 2ND NEWS UPDATE **

Another schematic was uploaded to post #1. This "DMA FIX" version is for A3000's which develope SCSI DMA transfer errors when they get very hot. It requires an extra jumper connection to the A3000's delay line to modify the CLK90 timing to -5ns! It will also add 1 wait state to ROM cycle timing so use it only if you need it. Although, that's a small price to pay considering the cut and jumper mod needed to separate Ramsey's CLK90 from Fat Gary's CLK90.

Speaking of Ramsey he is the primary suspect for this problem since SuperDMAC runs exclusively from CPUCLK. The problem appears to be with Ramsey's ACR (a special register used only for DMA). The CPU writes to this register so Ramsey can generate the address needed for DMA. SuperDMAC does not write to this register but sends Ramsey an INC_ADDR signal during DMA which points the finger back at Ramsey again for generating a proper address during DMA.

I will make an educated guess that Ramsey is different from the other custom chips in that it uses CLK90 as primary basic clock rather than CPUCLK. This could explain why the well known delay line hack (which creates a 5ns CLK90) allows Ramsey to operate at clock speeds well above 28 MHz.

Now, if I were AndyLandy I would not be surprised that the big C= would do such a thing!

P.S. I've added some images of an LHA loop script to continuously test my A3000. If a DMA transfer error occurs the script exits with an "Operation not entirely successful" message. So far 4 hours and counting with case reassembled and extra heat from my GVP Spectrum graphics card!

 

[droopy]

I have a couple of 07 ramsey I dont use.
If anyone serious is interested of buying one I might sell.
my own price was usd 49 each plus shipping and I can not do better than that
(59 usd) I would prefer 10 usd profit so I would like 69 usd.

I will consider to trade for something else unusual for A4000 with + or - money between.

( I socked my ramsey with a dremel and it works fine I have 2 extras in my drawer never mounted or used)

 

[SpeedGeek]

** 3RD NEWS UPDATE **

The 68030 State Machine mod archive has been updated (to fix a problem with the A3000T) and may be subject to further updates for the A4000T. Also, the 50 MHz schematic has been revised a little but I have not had time to do the update.

@droopy

If you have some items you would like to sell please post them in a "For Sale" Thread. Thank you!

 

[alenppc]

@SpeedGeek

I am going to try this mod soon, when I get the necessary hardware. If installed in an A4000, does the A4000 motherboard need to be jumpered as if you were using a 68030 card?

Also, is a 100 mhz crystal required on the card?

 

[SpeedGeek]

@allenppc

As previously posted this is a combination of 3 separate mods, it's make no difference if you use a 100 MHz oscillator or clock doubler as long you provide skew compensation between the 2 clocks. The A4000 mobo would need an additional jumper as previously posted.

 

[alenppc]

@SpeedGeek, thank you for the reply. I have read all the info I could find about these mods, but I am still having some trouble understanding everything, I am not a hw engineer.

So if I got this correctly, for an A4000:
- the motherboard should be jumpered to the internal clock (J188 > INT)
- GALs U203, U204, U205, U207, U208 programmed with your software included in the first post archive and soldered back;
- 68040 replaced with a 40 Mhz version (still trying to source this one) and the clock with a 100 Mhz one;

So if I got this right, this should be sufficient. From what I understand this would not work with an 80 MHz clock since it needs to be a multiple of 25.
Did I miss anything?

Also, I am having trouble sourcing GAL/PLD16V8-7 as mentioned in your readme; Would GAL16V8B-15 ones work?

Thanks

 

[SpeedGeek]

@allenppc

You should have a good look at the A4000 schematics. If you are going to use the mobo 74F74 to generate the 25 MHz CLK then you need a jumper from the A3640 for the 50 MHz CLK. You also need the 25 MHz CLK from the mobo back to the A3640 but what happens when you set the CLK jumpers to INT?

You don't necessarily need a 40 MHz 040 (I did it with a 25 MHz 040). Overclocking the 040 will always be a case of your mileage will vary but your better off with an MC 040 than an XC 040 regardless of CLK speed ratings.

If you plan to run the state machine logic at 50 MHz you need 10ns GALs as a minimum. If you want to do the apollo630 version you can get by with slower GALs because it runs the state machine logic at 25 MHz. You can use any JEDEC compatible PLDs instead of GALs [i.e. PALCE16V8, ATF16V8].

The revised schematics have been uploaded! I also have an idea for a "Hybrid" mod which switches the state machine logic from 50 to 25 MHz at cycle start but I don't know when I'll find time to work on it.

 

[alenppc]

OK cool, thanks! I think I have grasped the concept a bit better now.

I think this mod is not for me at this point in time. Think I will try the delay line + 66 Mhz clock mod instead once I get the 40 MHz CPU. My card has the original XC68040/25 which gets very hot so I'd rather not overclock that one.

 

[hooverphonique]

I was wondering.. the 8 clock latency A3640 mobo memory access includes the ramsey latency, I guess.. does this 8 clock latency hold for the 4 or 5 clock ramsey cycle, i.e. how many clocks latency is introduced by a stock A3640 itself (must be either 3 or 4) ?

 

[SpeedGeek]

I was wondering.. the 8 clock latency A3640 mobo memory access includes the ramsey latency, I guess.. does this 8 clock latency hold for the 4 or 5 clock ramsey cycle, i.e. how many clocks latency is introduced by a stock A3640 itself (must be either 3 or 4) ?

You have practically answered your own question. From Ramsey's point of view it runs either a 4 or 5 CLK cycle (except in the case of a burst or page mode cycle which are multiple transfer cycles). However, even with the 030 CPU (which eliminates the 030 state machine logic) it becomes either a 5 or 6 CLK cycle because it takes 1 CLK for Ramsey to detect the cycle start.

Since, Ramsey will add a minimum 2 CLK pre-charge time period between memory cycles there is only a 1 CLK cycle start + 1 CLK late termination penalty for the stock A3640.

P.S. The last penalty to be eliminated is the Ramsey 1 CLK cycle detection, but you have to run the CPU and state machine logic at 2X CLK speed to eliminate it.

 

[hooverphonique]

I was wondering.. the 8 clock latency A3640 mobo memory access includes the ramsey latency, I guess.. does this 8 clock latency hold for the 4 or 5 clock ramsey cycle, i.e. how many clocks latency is introduced by a stock A3640 itself (must be either 3 or 4) ?

Since, Ramsey will add a minimum 2 CLK pre-charge time period between memory cycles there is only a 1 CLK cycle start + 1 CLK late termination penalty for the stock A3640.

ok.. am I to understand this as the A3640 1 clk cycle start + 1 clk late term are not included in the 8 clock latency then, but they are all due to ramsey (1 detect, 5 mem access, 2 pre-charge) ?

I will try your state machine mod soon, btw.. just waiting for dip<->plcc adapters to arrive

 

[SpeedGeek]

ok.. am I to understand this as the A3640 1 clk cycle start + 1 clk late term are not included in the 8 clock latency then, but they are all due to ramsey (1 detect, 5 mem access, 2 pre-charge) ?

I will try your state machine mod soon, btw.. just waiting for dip<->plcc adapters to arrive

No, they are not all due to Ramsey. If that were the case, then how can you save 2 wait states with the state machine mod?

Try this instead:
(1 detect, 5 mem access, 2 state machine penalty)

 

[hooverphonique]

No, they are not all due to Ramsey. If that were the case, then how can you save 2 wait states with the state machine mod?

Try this instead:
(1 detect, 5 mem access, 2 state machine penalty)

yeah.. that's what I thought at first, just got thrown off by your precharge comment

 

[SpeedGeek]

** 4TH NEWS UPDATE **

Post #16 has been updated to explain a previously undocumented feature with the new state machine logic (intended to support overclocked A3640s). So far it's been working good on my A3000 but of course your mileage will vary (and A3640 overclockers know this quite well by now).

 

[dougal]

My A3640 is with a 66Mhz xtal and clocked at 33Mhz.

Does your mod require me to solder etc.. ? I am not good at that.

Can anyone do the mod for me ?

 

[SpeedGeek]

@dougal

I suggest you post a wanted thread here on Amibay for someone to mod your A3640. If no one reply's to your wanted thread with a satisfactory offer, then there is a banned member who may be willing to do it for you.

 

[Lozspd4]

Hi Speedgeek
Many Thanks for this mod and a special Thanks to Cosmo for the Gals spent the weekend soldering the new gals on and then testing with 040 worked perfect WOW. Then fitted the 040 > 060 Adapter which i put together runnuing at 60mhz (havent got a 66mhz quarz at the momment sob ) guess what double WOW. All we need now is a better way to expand the ram on the mother to 64 or 128mb then its perfect, the mediator ram on VGA is bottlenecking a bit so i turned it off. This is one perfect mod. again many thanks.

Regards Laurence

 

[KGC210]

Hi Speedgeek
Many Thanks for this mod and a special Thanks to Cosmo for the Gals spent the weekend soldering the new gals on and then testing with 040 worked perfect WOW. Then fitted the 040 > 060 Adapter which i put together runnuing at 60mhz (havent got a 66mhz quarz at the momment sob ) guess what double WOW. All we need now is a better way to expand the ram on the mother to 64 or 128mb then its perfect, the mediator ram on VGA is bottlenecking a bit so i turned it off. This is one perfect mod. again many thanks.

Regards Laurence

Have you seen this Laurence?
https://www.amibay.com/showthread.php?57613

Going to giving these mods ago myself soon. Just waiting on a few parts.