SpeedUp-16 - Unknown 16MHz accelerator

[jakesdad77]

Dear All.
I have a very nice Mega 1 that came from Germany via a UK Ebay seller. This Mega 1 has had a lot of mods. There are a lot of wires for the DIY TOS 2.6 board, 16MHz accelerator, HD Floppy disk drive and RAM upgrade to 3mb (yes 3mb which is not a usual number). The TOS 2.06 board works great, but the accelerator runs only at 8MHz. One of the first things I noticed was the 16MHz feed from the Video Shifter. I lifted up the 68000 CPU to look for a way to identify the accelerator board. It says 'SpeedUp-16' on the PCB, and 68000/16 in additional print. Please see photos.

Can anyone identify this accelerator board please? I am looking for the original instructions (if they exist), so I can understand more about this particular board. It does not look like the other 'usual' 16MHz accelerators that have been discussed before (unless I have just not found the discussions/photos).

Thanks James

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[czietz]

dev-docs has some instructions (in German, of course): https://docs.dev-docs.org/htm/search.php?find=speedup. They are not particularly interesting, but they mention it's a project from the German magazine c't, issue 10/1990. The magazine article has a more detailed description (in German, of course and pay-walled): https://www.heise.de/select/ct/archiv/1990/10/seite-330.

So what I gather from the article, the SpeedUp-16 is a 16 MHz accelerator, albeit without cache. ROM accesses run at full speed. By design, it cannot accelerate ST-RAM accesses. The article mentions that the 8/16 MHz switch signal (a solder pad named "C") can be generated by a mechanical switch or by using a free pin of the PSG sound chip. I can't see how it's wired in your system, though.

EDIT: The solder pads, according to the article: Between "A" and "B" you can connect a "turbo LED", with a suitable series resistor. "C", as already mentioned, is the input to switch between 8 and 16 MHz. "D" is the 16 MHz clock input, and "E" is the associated ground for the clock. "F" is an input for the chip select signal of the PSG sound chip, because apparently there were some issues when accessing the sound chip in 16 MHz mode, and the circuit needs to handle sound chip accesses in a special way.

[jakesdad77]

Many thanks czietz.

Your info is pretty much spot-on for this particular Mega 1. Excellent, thank you for that. I have verified that the A - F connections are all there except the GND. One of the wires is a piece of coax (thick grey one). The GND is attached on the CPU board, but not on the other end. I have soldered on another piece of wire to act as a GND to a piece of metal on the case. So the the 16Mhz pin from the video shifter and the GND are going down a piece of coax!! I have taken some more photos, but had to remove my 'new' GND wire for now, and remove the PSU. So if the brown wire that goes to the Yam chip (from point C) is a free pin, then this is ok. The red wire that goes to the 'select signal' chip is confusing me right now, as it goes to another small chip that I don't know much about. Please see the photos and any help would be great.

I did not know that the sound chip had problems with 16Mhz. This does explain why my HBS 240 accelerator also can be soldered to the sound chip(s) too, but I don't think I have tested sound using my HBS 240 yet!!! At least now I understand what else I need to do for that now.

Oh, and the Mega 1 that I am using for the Speed-Up 16 does not have IMP chips.
Thanks again J

[jakesdad77]

forgot the photos!!!

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[jakesdad77]

Update.

I turned my attention to the Yam sound chip. I found whoever has soldered the brown wire to the Yam chip, had soldered to the wrong pin (or soldered to any pin to make it work at 8MHz Only). I located the 'Chip Select' pin and soldered the brown wire to this pin (pin 26). Result. Gembench 6 now reports 193% Integer Division (up from 99%) and ROM speed is now 171% (up from 99%). Will upload Gembench 6 results soon. Many thanks czietz, I needed someone with more experience and brain power to make me realise where to look. Hope I get to your level one day!! :D

Sysinfo still reports 8MHz but then again, by HBS 240 card does this, and so does my Exxos 32Mhz STe, so I knew it wasn't unusal.

More to follow.

Regards James

[czietz]

Maybe the colors come up wrong on your photos. But according to the instructions, the brown wire, i.e., the one going to solder pad "C", i.e. the one that switches between 8 and 16 MHz should NOT be connected to the chip select signal of the PSG. Solder pad "F" is to be connected to the chip select signal of the PSG.

The 8/16 MHz switch signal (solder pad "C") can be connected either to a mechanical switch or to port A7 of the PSG, pin 14. Of course, you need a small program that switches port A7 to switch the speed.

EDIT: The download for the 10/1990 issue of c't magazine has a program (source code for Turbo Assembler) that switches port A7 when you press both Shift keys at once. Look for file CT1090S.334 in https://ftp.heise.de/ct/listings/ct9010.zip.