Today I overclocked my A3010

[vectorlight]

direct into the ARM250 in place of the 36MHz clock...?

Yeah, looking at the ARM250 datasheet the video clock comes out on pin 123 and goes back in on pin 124 so maybe giving the possibility to override the clock speed at pin 124.

[vectorlight]

Just out of interest i tried 800x600 in 256 colours on a normal 12mhz A3020 and it seems to work okay. I guess its different on each machine whether it will work or not. Having said that, although it works the desktop is far too slow for it to be useful

[steve3000]

Just out of interest i tried 800x600 in 256 colours on a normal 12mhz A3020 and it seems to work okay. I guess its different on each machine whether it will work or not. Having said that, although it works the desktop is far too slow for it to be useful

That is intesting. Thinking about this, I've not actually tried that mode before on an ARM250 - only on an A5000, A540 and A310 - all of which displayed the screen, but with 'sparkling' pixels... Maybe time for some experiments this weekend...

[vectorlight]

Heres a quick video comparing the desktop redraw speed @ 800x600 in 256 colours. 12mhz on the left. 26mhz on the right. Seems to work okay at 12mhz and theres even enough memory bandwidth left to kindof use the desktop:

https://www.youtube.com/watch?v=5cIclkEq2y0

[AndyMc1280]

Here is the final design (almost anyway, want to tidy up some tiny things). I'll start ordering stuff tomorrow.

Any progress? been a while. I've not been around much anyway.

Ok, I have attached my 'Mode 32' equivalent here - it's actually MODE 127, so load it up and enter MODE 127...

800 x 600 in 256 colours = 469kb, pretty much the maximum mode size possible on the VIDC1/MEMC Arc.

Question is, does it work?

I need to try this - previous efforts at getting mode 32 working have resulted in shimmering screen I shall have a play.

[steve3000]

Just out of interest i tried 800x600 in 256 colours on a normal 12mhz A3020 and it seems to work okay. I guess its different on each machine whether it will work or not. Having said that, although it works the desktop is far too slow for it to be useful

Still pondering why you didn't get shimmering pixels on your normal A3020... I found my notes from when I tried this mode on my A4000, which is pretty much identical to the A3020, and I noted down that I saw shimmering pixels.

Had you replaced the RAM on the A3020 which you tested, or was it stock RAM at 12Mhz?

[steve3000]

Just out of interest i tried 800x600 in 256 colours on a normal 12mhz A3020 and it seems to work okay. I guess its different on each machine whether it will work or not. Having said that, although it works the desktop is far too slow for it to be useful

Still pondering why you didn't get shimmering pixels on your normal A3020... Today I found my notes from when I tried this mode on my A4000, which is pretty much identical to the A3020, and I certainly noted seeing shimmering pixels. (Andrew also mentions above that he saw shimmering pixels too). Maybe the mode is right on the limit of what's possible with 12Mhz RAM, and some computers can handle it/some can't?

Unless your A3020 was modified in some way? Had you replaced the RAM on the A3020 which you tested with faster RAM (but kept clock at 12mhz), or was it stock RAM at 12Mhz? or did it have a RAM upgrade from bitd?

[vectorlight]

Still pondering why you didn't get shimmering pixels on your normal A3020... Today I found my notes from when I tried this mode on my A4000, which is pretty much identical to the A3020, and I certainly noted seeing shimmering pixels. (Andrew also mentions above that he saw shimmering pixels too). Maybe the mode is right on the limit of what's possible with 12Mhz RAM, and some computers can handle it/some can't?

Unless your A3020 was modified in some way? Had you replaced the RAM on the A3020 which you tested with faster RAM (but kept clock at 12mhz), or was it stock RAM at 12Mhz? or did it have a RAM upgrade from bitd?

Hi Steve,

Yep, the A3020 had all its RAM (2mb) replaced with 28ns RAM, but for this particular test it was running at 12mhz. Given that the 800x600x8bpp uses 26mb/s and 12mhz RAM provides 36mb/s in bandwidth there shouldn't be an issue with video bandwidth, but then I'm no expert with this stuff...

[AndyMc1280]

Just out of interest i tried 800x600 in 256 colours on a normal 12mhz A3020 and it seems to work okay. I guess its different on each machine whether it will work or not. Having said that, although it works the desktop is far too slow for it to be useful

Still pondering why you didn't get shimmering pixels on your normal A3020... Today I found my notes from when I tried this mode on my A4000, which is pretty much identical to the A3020, and I certainly noted seeing shimmering pixels. (Andrew also mentions above that he saw shimmering pixels too). Maybe the mode is right on the limit of what's possible with 12Mhz RAM, and some computers can handle it/some can't?

Unless your A3020 was modified in some way? Had you replaced the RAM on the A3020 which you tested with faster RAM (but kept clock at 12mhz), or was it stock RAM at 12Mhz? or did it have a RAM upgrade from bitd?

To add to this, My A3010 with the ram at 12 Mhz Displays Mode 127 as provided by Steve, the text is a wee-bit blocky and it is not very pleasant to work with. there's also stutter when dragging windows around and on floppy access the screen flashes on and off.
I'm assuming you guys are using *con. monitortype 4 as the setting (SVGA) ?

I've not tried it with my R260 since it got a Colourcard Gold, that SHOULD handle it, I would hope, unless the card is knackered

[steve3000]

To add to this, My A3010 with the ram at 12 Mhz Displays Mode 127 as provided by Steve, the text is a wee-bit blocky and it is not very pleasant to work with. there's also stutter when dragging windows around and on floppy access the screen flashes on and off.
I'm assuming you guys are using *con. monitortype 4 as the setting (SVGA) ?

I've not tried it with my R260 since it got a Colourcard Gold, that SHOULD handle it, I would hope, unless the card is knackered

Thanks for testing! The blocky text means it's not working, the data isn't getting out fast enough, so some pixels are repeated making it blocky.

The switching off and on during floppy access is a feature of RISC OS to ensure that floppy data is able to be read at the correct rate in high bandwidth modes.

Colourcard won't make any difference, at least I assume it won't, because it requires special modes to use its hardware, and I have no idea how to design modes which use the colourcard.

[steve3000]

Yep, the A3020 had all its RAM (2mb) replaced with 28ns RAM, but for this particular test it was running at 12mhz. Given that the 800x600x8bpp uses 26mb/s and 12mhz RAM provides 36mb/s in bandwidth there shouldn't be an issue with video bandwidth, but then I'm no expert with this stuff...

I need to do the calculations, but that 26mb/s is an average over 1 second including vertical refresh time, when no data is required. During the DMA phase, the effective data requirement over the 800 pixels of the line will be higher than 26mb/s, and that could be the issue.

[AndyMc1280]

I'd still like to try out those 28ns RAMs after this, but at least to start with the expansion will only be 1M. That should be enough to see how fast the rest of the system can go, then if it's worth while I'll see about a larger/faster expansion.

Did some of you guys have spare 50ns RAMs? Occurred to me that I could buy some of your spares instead of ordering more if unless you need to save them for something.

Any progress on this? I know I keep rattling on but I was wondering, and it has been 2 months since I last asked

[munchausen]

I'd still like to try out those 28ns RAMs after this, but at least to start with the expansion will only be 1M. That should be enough to see how fast the rest of the system can go, then if it's worth while I'll see about a larger/faster expansion.

Did some of you guys have spare 50ns RAMs? Occurred to me that I could buy some of your spares instead of ordering more if unless you need to save them for something.

Any progress on this? I know I keep rattling on but I was wondering, and it has been 2 months since I last asked

Yeah I know, sorry for the delay. It took me a lot longer than I thought to get my thesis fully wrapped up (been chasing maths for two months), and that has sucked up all my spare time (as I've been doing it part time while working), but I'm finally finished !

So I first want to get my A3010 working properly, the PSU is more-or-less dead, I have to turn it off and on more than 30 times to get it to turn on with a stable 5V line so that it actually boots, which makes it impossible to get anything done. I've ordered parts to sort that out this week, so when I've got it working I will order PCBs and other parts for the memory expansion. I'll keep you posted.

[AndyMc1280]

Yeah I know, sorry for the delay. It took me a lot longer than I thought to get my thesis fully wrapped up (been chasing maths for two months), and that has sucked up all my spare time (as I've been doing it part time while working), but I'm finally finished !

So I first want to get my A3010 working properly, the PSU is more-or-less dead, I have to turn it off and on more than 30 times to get it to turn on with a stable 5V line so that it actually boots, which makes it impossible to get anything done. I've ordered parts to sort that out this week, so when I've got it working I will order PCBs and other parts for the memory expansion. I'll keep you posted.

No worries! I remember the pain of my own dissertations. Yes plural I loved it so much I did two undergraduate and masters. *Shudders*

Thanks for the reply. Hopefully you get your A3010 sorted soon

[munchausen]

I've just ordered 10 PCBs, they're going to take at least a couple of weeks to arrive. I also ordered an SMD rework station yesterday to do the work.

I still need to get a few bits like paste and flux, and the pin headers and RAM itself. With regards to the RAM, can I buy a couple of spare chips from someone to begin with (I know I mentioned this before)? I'd like to check the design is OK before committing to ordering a large number of them.

[vectorlight]

I've just ordered 10 PCBs, they're going to take at least a couple of weeks to arrive. I also ordered an SMD rework station yesterday to do the work.

I still need to get a few bits like paste and flux, and the pin headers and RAM itself. With regards to the RAM, can I buy a couple of spare chips from someone to begin with (I know I mentioned this before)? I'd like to check the design is OK before committing to ordering a large number of them.

Hi munchausen,

Great news PM me your address and I'll send you the spare RAM I have.

[munchausen]

The boards arrived, and on initial inspection they look perfect - the main connectors are the exact distance apart to fit in the A3010, and the RAM footprints match the RAMs vectorlight sent me (the two things I had a slight concern over).

[vectorlight]

It looks great, fingers crossed it works

[steve3000]

These look great - well done! Can't wait to see them populated and working.

[vanpeebles]

Is this going to be a remake of the simtec turbo ram?

[vectorlight]

Is this going to be a remake of the simtec turbo ram?

It's a clone of the IFEL 4MB memory board. It's going to have 26mhz RAM on it. Not sure how fast the Simtec turbo board RAM was?

[vanpeebles]

I'm not sure. I remember than the turbo ram made your machine run faster though. I was heart broken because I finally saved enough to buy a turbo ram, and my mam rang simtec only to be told that it was discontinued, because they struggled to get the right speed of chips.

[vanpeebles]

An old post by someone on the iconbar stated

"Right, here we go. The 'Turbo RAM' upgrade was a 4MB upgrade that used some stupidly-fast 40-50ns 4Mbit FPM memory (8x 1Mx4). Usually, upgrades at the time used 70/80ns. The upgrade also replaced the memory system clock of the ARM250 to clock the memory at higher speeds. The default 36MHz clock was replaced with a 40, 42, 44.5, 48, 50, 55, 60 or 64MHz part, depending on on quick it went and then backing off a bit, and then tested with elevated temperatures to check it still worked.

The upgrade would not work if the machine had a mezzanine board (ARM2+VIDC+IOMD+IOC on a PCB instead of the ARM250), but it is possible to upgrade it to an ARM3.

Somewhere there is a PDF with installation instructions. I'll see if I can dig that out.

The parts to do this upgrade are staggeringly difficult to find now, so it is unlikely to be reproducible."

http://www.iconbar.com/forums/viewthrea ... adid=11344

[vectorlight]

I see, thanks for the info. I had heard of this upgrade before but didn't know what it did. This board that munchausen is making will be faster then, I've tested some overclocked Micron RAM chips with an 80mhz crystal which gives you a stable and speedy 26.6mhz machine.

[AndyMc1280]

An old post by someone on the iconbar stated

"Right, here we go. The 'Turbo RAM' upgrade was a 4MB upgrade that used some stupidly-fast 40-50ns 4Mbit FPM memory (8x 1Mx4). Usually, upgrades at the time used 70/80ns. The upgrade also replaced the memory system clock of the ARM250 to clock the memory at higher speeds. The default 36MHz clock was replaced with a 40, 42, 44.5, 48, 50, 55, 60 or 64MHz part, depending on on quick it went and then backing off a bit, and then tested with elevated temperatures to check it still worked.

The upgrade would not work if the machine had a mezzanine board (ARM2+VIDC+IOMD+IOC on a PCB instead of the ARM250), but it is possible to upgrade it to an ARM3.

Somewhere there is a PDF with installation instructions. I'll see if I can dig that out.

The parts to do this upgrade are staggeringly difficult to find now, so it is unlikely to be reproducible."

http://www.iconbar.com/forums/viewthrea ... adid=11344

We must have been "upgrading to 4MB" at the same time... I phoned Simtec and got the *very last* Super turbo board they had which must've been a 60/64Mhz one as performance was beyond an Arm3 A5000 at school. Feel free to hate me

Stupidly I sold that machine and have regretted ever since Although my (currently poorly) Arm 3 A3010 at 30 mhz somewhat makes up for it (need to fix, I suspect a cap has gone somewhere, it won't boot) and will be even quicker with one of these ram upgrades

[vanpeebles]

*Shake fist*

[danielj]

By the looks of things they also produced a super-turbo for the A3020... I haven't looked at the schematics in detail, but is it therefore possible to jumper an A3020 to bypass the internal RAM and just use what's on a plug-in board?

d.

[AndyMc1280]

*Shake fist*

Wuv ooo too

[vectorlight]

Have you managed to test any of these munchausen? I'm in need of another 4MB board for a project and I was hoping to avoid paying £90 to CJE for one

[Zarchos]

Have you managed to test any of these munchausen? I'm in need of another 4MB board for a project and I was hoping to avoid paying £90 to CJE for one

Another great project for the community ?
In that case you're entitled to get a free one from me