Qzero with SRAM extension reaching 40 MHz 68040

[Peter]

Hi Derek,

Personally, I am not worried by the increased cost of SRAM, but but much more expensive would to have the Qzero use fast ram completely and not use slow ram?

About 150 € if purchased from authorized distributors. Potentially more than a 68EC060CPU.

Not knowing exactly what the use of slow ram compared to fast ram, could slow ram be eliminated, for greater speed?

"Slow" means normal Qzero speed, still quite fast for an FPGA design, since video RAM is separate. It does not suffer from memory contention as Q68 and QIMSI Gold. Still the SDRAM Qzero does not play in the same league as an SRAM Qzero, which boosts it to half Q60/66 speed according to the Q-Top benchmark.

Of course, SDRAM could be disabled completely, to use it as a 4 MB (plus video RAM) "always fast" FPGA machine.

[Peter]

Yesterday I played around with my memory hungry QPC setup using 4MB of RAM. I found it perfectly usable, 8MB was ample for my needs.

Thanks for this feedback. This coincides with my own experience.

The zero has separate video memory so I assume this reduces the need for "main memory" considerably, especially at maximum resolutions.

Yes, that is correct. The newest Q68 SMSQ/E (which is also used for Qzero) will even move the (up to 1.5 MB) temporary storage for BGIMAGE to video memory.

[Peter]

Any way you can set some sort of "afinity" flag so certain types of code will always go to the faster memory?

That sounds like a serious OS change, maybe not justified. If memory grows into the "slow" region, everything that has been allocated before, remains fast. Especially the extensions and OS portions. Applications inside the "slow" region would still benefit from that.

[Derek_Stewart]

Hi,

I generally use a QPC2, SMSQmulator or sQLux, 2Mb system, which is enough memory for the Extended Enivronment, Prowess, with QMAC, QLINK, QD, Qliberator, memory resident. I never run out of memory, even when compling a C68 or Turbo program.

SMSQ/E is such an efficient operating system, that the scheduling of memory resident programs or Things, makes the most of available memory.

The 32Mb on the Q68, is wonderful, I can forget about memory running out, the Qzero, much faster with no memory contention.

I would say 2-4Mb is a reasonable about of memory.

I do not think the cost is s ptoblem, look at the Vampire 4 Standalone, retails at over €500, but still sells very well.

Not a good comparison, neither is thd Spectrum Next ti the Q68 as stated in the video presentation, that sells for double the cost if the Q68. They sell many Next systems.

[Peter]

I would say 2-4Mb is a reasonable about of memory.

I find 2 MB insufficient. In many cases, I could probably live with 4 MB, given the upcoming new SMSQ/E background image handling.
But there are users who need more, e.g. many instances of editors, or displaying large images.
The Qzero has SDRAM anyway. That's why I consider the afformentioned SDRAM+SRAM hybrid.

I do not think the cost is s ptoblem, look at the Vampire 4 Standalone, retails at over €500, but still sells very well.

That one plays in the upper 68060 league. While a Qzero with SRAM is only comparable to a good 68040 system for QL purposes.