Ram speeds with Accelerators

[Toryglen-boy]

Howdy. Looking for some advice on RAM speeds with SIMM's in accelerators. Whats the best, and fastest and best RAM you can chuck into something like a Blizzard 1230? 50 or 60ns? Does speed of the RAM make a difference? does parity come into it? can you control the wait states?

Lookin' at puttin a faster xtal on a Blizzard, and overclocking the 68030 on it slightly, up to 60Mhz if i can. i am guessing as long as i am not pushing it too hard, the RAM would be the crucial factor?

But why i hear you ask? because i can, in much the same way i used to buy a box of matches when i was a wee boy in 70's and torch anything that wasn't tied down. because i can, and i want to

[Kelv]

I wouldn't do it if your board has an FPU from memory they don't overclock very well ( sure someone better informed can comment ). I don't think your going to get the performance boost your looking for.
Still learning about accelerators myself but in theory a big heatsink and as fast a memory as you can find will avoid wait states / cache misses.

Looks like some have had success with o/c'ing it to 66Mhz:
https://translate.googleusercontent....FzxxFjufVZTgHw

Me I would be really cautious about 'popping' the card and would do a lot more reading around first.
Good luck and cant wait to see how you get on with it.

[Toryglen-boy]

Originally Posted by Kelv

I wouldn't do it if your board has an FPU from memory they don't overclock very well ( sure someone better informed can comment ). I don't think your going to get the performance boost your looking for.
Still learning about accelerators myself but in theory a big heatsink and as fast a memory as you can find will avoid wait states / cache misses.

Looks like some have had success with o/c'ing it to 66Mhz:
https://translate.googleusercontent....FzxxFjufVZTgHw

Me I would be really cautious about 'popping' the card and would do a lot more reading around first.
Good luck and cant wait to see how you get on with it.

it has no FPU, i wouldn't dream of clocking it with an FPU, it will just "pop".

as long as there is a heatsink on there, and the RAM can handle it, i might be ok.

[trixster]

Atari owners have had success overclocking 33 and 40mhz 68882s to 50mhz and beyond in Falcons without much issue.

Example: http://www.atari-forum.com/viewtopic.php?t=28947

[Daedalus]

FPUs tent to tolerate overclocking easily as much as their CPU counterparts, though as you suggest, heatsinks would be required. RAM speed doesn't make a difference so long as it's fast enough, and most cards don't go any faster than 60ns, and are often 70ns. Parity isn't used on any Amiga cards that I know of either - 36-bit RAM can usually be used but the parity bits are ignored. If you can find 50ns RAM, then at least you can be sure that it's not causing any instability that results from overclocking.

With A1200 cards however, you're also limited by the glue logic, RAM controller, SCSI controller and whatever else is on the card, so even if you CPU and FPU are capable of being overclocked, you could still have crashes and general instability due to overheating of a GAL or a ROM chip not keeping up or something.

Given that some ACA cards are shipped running 030s at 55MHz, that could be a decent starting point. If you replace the crystal with a modified DIL socket, you'll be able to easily swap crystals to see what speed you can run at reliably, but don't expect miracles.

[HelloBeautiful]

I have a late revision 68882 in my GVP that's clocked from 40 to 50 without problems.
The ACA cards from iComp have the fastest memory in the market so they perform very well compared to the cards from the 90s with the same or less CPU specs.

[Toryglen-boy]

Originally Posted by Daedalus

FPUs tent to tolerate overclocking easily as much as their CPU counterparts, though as you suggest, heatsinks would be required. RAM speed doesn't make a difference so long as it's fast enough, and most cards don't go any faster than 60ns, and are often 70ns. Parity isn't used on any Amiga cards that I know of either - 36-bit RAM can usually be used but the parity bits are ignored. If you can find 50ns RAM, then at least you can be sure that it's not causing any instability that results from overclocking.

With A1200 cards however, you're also limited by the glue logic, RAM controller, SCSI controller and whatever else is on the card, so even if you CPU and FPU are capable of being overclocked, you could still have crashes and general instability due to overheating of a GAL or a ROM chip not keeping up or something.

Given that some ACA cards are shipped running 030s at 55MHz, that could be a decent starting point. If you replace the crystal with a modified DIL socket, you'll be able to easily swap crystals to see what speed you can run at reliably, but don't expect miracles.

thanks mate, that's as i thought.

[whiteb]

Originally Posted by Toryglen-boy

Howdy. Looking for some advice on RAM speeds with SIMM's in accelerators. Whats the best, and fastest and best RAM you can chuck into something like a Blizzard 1230? 50 or 60ns? Does speed of the RAM make a difference? does parity come into it? can you control the wait states?

If you have the choice, out of 50 or 60ns ram, use the 50ns. it is hardly noticeable, but the 50ns is 10ns faster

[matthey]

Originally Posted by whiteb

If you have the choice, out of 50 or 60ns ram, use the 50ns. it is hardly noticeable, but the 50ns is 10ns faster

There can be a difference between what memory is rated (usually printed on the chips) and what you actually get. Some memory can run much faster than what it is rated much like many CPUs can clock much faster than rated. Just like a faster clocked CPU, higher clock rated memory is no faster unless running at higher clock speeds (which often happens when overclocking the CPU). It is getting more difficult to find 50ns SIMMs and 60ns SIMMs will usually be adequate for a moderate amount of overclocking. Just run some memory tests in warm conditions. If there are errors and you have a pile of 60ns SIMMs then try some others before forking over much for 50ns memory.

[Kin Hell]

Just to add to matthey's excellent advice above, and to say of my experiences over the years, some of the later 60ns 72Pin SIMMS in the guise of EDO can allow good 060's to go further with their over-clocks. Later/newer Ram had better manufacturing facilities & then you get those sweet wafers of Silicon.

& yes, 50ns always looks better than 60ns, even if you're not using it!