Upgrading Q40 to 68060 CPU

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Silvester
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Upgrading Q40 to 68060 CPU

Post by Silvester »

Peter wrote:
Derek_Stewart wrote:I hoped to use a 68060RC50A so that it would run at full speed of 50 Mhz. I did not complete this, as the Q68 got in the way.
Don't forget there never was PLD support for 50 MHz. If you use a 50 MHz oscillator with a PLD designed for higher speed, you will get inefficient DRAM timings and a wrong frame interrupt frequency. Only 60/66/80 MHz are supported.
But the 68060RC50A runs fine at 60 MHz on that mainboard.
Slight confusion, Peter are you referring to Q40/Q60 PLD ? I think Derek was contemplating adding 68060RC50A to QXL via adapter.

Sadly from what I have seen so far, non-EC 68060 command x8 to x10 the price of EC. Didn't think SMSQ/E used MMU, must delve into Q40 source :!:

Just to confirm, 68060 for Q40 must be have speed capability of 60, 66 or 80MHz ?


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Re: Upgrading Q40 to 68060 CPU

Post by Derek_Stewart »

Silvester wrote:
Peter wrote:
Derek_Stewart wrote:I hoped to use a 68060RC50A so that it would run at full speed of 50 Mhz. I did not complete this, as the Q68 got in the way.
Don't forget there never was PLD support for 50 MHz. If you use a 50 MHz oscillator with a PLD designed for higher speed, you will get inefficient DRAM timings and a wrong frame interrupt frequency. Only 60/66/80 MHz are supported.
But the 68060RC50A runs fine at 60 MHz on that mainboard.
Slight confusion, Peter are you referring to Q40/Q60 PLD ? I think Derek was contemplating adding 68060RC50A to QXL via adapter.

Sadly from what I have seen so far, non-EC 68060 command x8 to x10 the price of EC. Didn't think SMSQ/E used MMU, must delve into Q40 source :!:

Just to confirm, 68060 for Q40 must be have speed capability of 60, 66 or 80MHz ?
HI,

Sorry for the confusion, I was referring to the upgrading of the QXL 68EC040 to a 68060 CPU using an adapter developed for the Amiga. Which is a two board adapter that splits the 68040 5v levels and 68060 3.3v levels on separate PCBs. I have 2 sets of PCBs to be built.

The QXL 2 was fitted with a 50Mhz Oscillator which the 68040 CPU divides the clock speed by 2 to 25Mhz. So I thought why not take the Amiga 68040-060 Adapter board and fit a 68060 50Mhz to the QXL, this may run the QXL at 50Mhz, but I guess like is not that easy, and probably SMSQ/E will not work, the QL Network will not work. I will have to finish work and see if it is successful.

I have 4 QXL2 board built and a bare PCB, which I do not think they are available for sale as yet.

I never produced a Q40, these were made by Tony Firshman and later by Qbranch, the Qbranch Q40 boards had problems - poor construction and inferior components, which a friend and I stepped in to build the Q60.

We did a Q40i, with 128Mb ram, but only one was sold.

The Q60, was designed by Peter Graf and sold in a production run by D&D Systems. and 3 varieties:

Q60-60: 68060 at 60Mhz, RC CPU, with FPU, MMU
Q60-66: 68060 at 66Mhz, RC CPU, with FPU, MMU
Q60-80: 68060 at 80Mhz, LC CPU, with no FPU

For later Q60 production, there only going to the Q60-66 to made available. But this was never implemented.

Due to changes in my day time job, I had to move from Derbyshire to Cheshire, in the UK, which sort of put the Q60 on hold, and Peter gave me the Q68 to produce, which made the Q60 pushed further down the project waiting list.

After I statisfied the Q68 demand, I will look at the a possible production of a updated Q60, assumnig that the 68060 CPUs are available.

There are alot of forged 68060 CPUs so care is needed in purchasing a geniue CPU.


Regards,

Derek
Silvester
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Re: Upgrading Q40 to 68060 CPU

Post by Silvester »

Thanks for info Derek.

I checked the SMSQ/E sources and it appears the MMU is only used if the config item 'Set up MMU for QLiberator' is on (smsq_q40_hwinit_asm).

So it should be OK to use EC version of 68060 (as long as you don't mind QLiberator option off - whatever that means I have yet to discover, perhaps if necessary an alternative fix can be found).

(PROT_MEM mentioned in Q40 guide to set up MMU has never been implemented.)


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Re: Upgrading Q40 to 68060 CPU

Post by Peter »

Silvester wrote:Slight confusion, Peter are you referring to Q40/Q60 PLD ? I think Derek was contemplating adding 68060RC50A to QXL via adapter.
Thanks, and you're right of course.
Silvester wrote:Sadly from what I have seen so far, non-EC 68060 command x8 to x10 the price of EC. Didn't think SMSQ/E used MMU, must delve into Q40 source :!:
The issue here is the cacheability for the various memory regions. Things start with ROM or ROM emulation area, then RAM, then screen, then RAM, then ROM again, then highres screen, then I/O. Where RAM is cacheable-copyback, ROM emulation and screen are (normally) cacheable-writethrough, I/O is cache-inhibited. Using the 68060 MMU, the cache modes can be described in a very detailed manner. And if I remember correctly, Tony Tebby did include a little MMU table in SMSQ/E for that purpose. (Not sure about it, and no time to dig into the sources at the moment.)

If there is no MMU, only the "Transparent Translation Registers" (DTTR0, DTTR1, ITTR0, ITTR1) are available to define cacheability, allowing fewer regions. This can be worked around for example by defining screen as cacheable-copyback and flush caches regularly, so screen is updated despite the "wrong" cachemode. Or by using cacheable-writethrough for both screen and RAM, which cripples the CPU speed massively.
Silvester wrote:Just to confirm, 68060 for Q40 must be have speed capability of 60, 66 or 80MHz ?
Yes, otherwise the 50 Hz interrupt would have a wrong frequency and DRAM access would be inefficient.
Note: 60/66 MHz requires reprogramming two PLDs.


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Re: Upgrading Q40 to 68060 CPU

Post by Silvester »

Wow, thanks for that info, I didn't realise the cache implications on the MMU. I'll have to blow the dust off my copy of MC68060 manual I got 25 years ago and read up on it. Meanwhile I'll have to look out for a MC68LC060RC75...

Looks like MMU tables are at end of smsq_q40_hwinit_asm


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Re: Upgrading Q40 to 68060 CPU

Post by Peter »

Silvester wrote:Wow, thanks for that info, I didn't realise the cache implications on the MMU. I'll have to blow the dust off my copy of MC68060 manual I got 25 years ago and read up on it. Meanwhile I'll have to look out for a MC68LC060RC75...
I had a very quick look and it seems that SMSQ/E already defines screen as cacheable-copyback, just like normal RAM, while flushing cache regularly for screen update.
Which means that your assumption about the MMU being used only for Qliberator issues, is probably right and the EC version can be used if you are not interested in Linux.

So if the LC version is much more expensive, I would encourage you to try the EC version. Sooner or later I will have a look at that issue anyway, and if EC does not work yet, somehow find a solution. And QDOS Classic does not need the MMU at all, so in the worst case you'd have at least some means to test the machine.

Do you already own a Q40 for that purpose?

How does the CPU socket on your board look with regard to adding the extra pins? You don't need all inner pins, only VCCs and GNDs plus D4, K15, P15, Q8, Q11, Q12, Q15. The rest is unconnected.


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Re: Upgrading Q40 to 68060 CPU

Post by RalfR »

What kind of QLiberator issues are there? Problems with MMU? I had never problems of that kind with an hyperCache 030 on the Atari.


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Re: Upgrading Q40 to 68060 CPU

Post by Silvester »

Peter wrote:I had a very quick look and it seems that SMSQ/E already defines screen as cacheable-copyback, just like normal RAM, while flushing cache regularly for screen update.
Which means that your assumption about the MMU being used only for Qliberator issues, is probably right and the EC version can be used if you are not interested in Linux.
My only interest is to have access to 68060 for programming in a comfortable enviroment, SMSQ/E.
Peter wrote:So if the LC version is much more expensive, I would encourage you to try the EC version. Sooner or later I will have a look at that issue anyway, and if EC does not work yet, somehow find a solution. And QDOS Classic does not need the MMU at all, so in the worst case you'd have at least some means to test the machine.
I had ordered a couple of MC68EC060RC75 from https://www.ebay.co.uk/itm/162502659921 but seller messaged me RC75 were sold out and offered to send RC66 instead, which I declined (immediately refunded, reliable seller with lots of positive feedback). Don't want to reprogram PLD for 66MHz, unless I can not get 75, then might have to go back a get 66 anyway :-(
Peter wrote:Do you already own a Q40 for that purpose?
I had one of the first ones (regrettably*) * I should qualify that: not produced by Derek, but others who I wish I had avoided.
Peter wrote:How does the CPU socket on your board look with regard to adding the extra pins? You don't need all inner pins, only VCCs and GNDs plus D4, K15, P15, Q8, Q11, Q12, Q15. The rest is unconnected.
BTW is it imperative that you obtain the right CPU extraction tool, or it OK to just be careful ?
Q40 circa 1999
Q40 circa 1999
Last edited by Silvester on Thu Apr 28, 2022 5:29 pm, edited 3 times in total.


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Re: Upgrading Q40 to 68060 CPU

Post by Silvester »

RalfR wrote:What kind of QLiberator issues are there? Problems with MMU? I had never problems of that kind with an hyperCache 030 on the Atari.
I had a look at SMSQ/E docs but couldn't find any reference to it (it is a config item). Look into it later (probably much).


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Re: Upgrading Q40 to 68060 CPU

Post by Peter »

Silvester wrote:Don't want to reprogram PLD for 66MHz, unless I can not get 75, then might have to go back a get 66 anyway :-(
I'm not 100% sure anymore, but it might be sufficient to remove a jumper to switch the PLD to 66 MHz mode. I'll check that if it is actually required.
(You'd still need a 66 MHz oscillator.) First let's hope you'll find 75 speed grade.
Silvester wrote:I had one of the first ones (regrettably*) * I should qualify that: not produced by Derek, but others who I wish I had avoided.
I also wish I had avoided them, several lost years for the Q60. And years were a lot, at a time when the design (first prototype in 1996) was not just "retro" but could compete with a PC performance-wise.
Silvester wrote:
Peter wrote:How does the CPU socket on your board look with regard to adding the extra pins? You don't need all inner pins, only VCCs and GNDs plus D4, K15, P15, Q8, Q11, Q12, Q15. The rest is unconnected.
BTW is it imperative that you obtain the right CPU extraction tool, or it OK to just be careful ?

DSCF0072.JPG
It is sufficient to just be careful. Regarding the CPU socket, I was more interested in the top side, to see in which way the additional pins could best be added.


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