Progressive Peripherals & Software (PP&S) A2000/040 overclock

[wmaciv]

Is there any data on the importance of refresh rates for this card? I am currently using two chip, 60ns rated 4MB SIMMS, 4K refresh from what I can tell. Is there any speed or stability advantage of going to a 1K / 2K refresh SIMM with this hardware? Nothing in the user manual makes any distinction about refresh rates. I am asking because the PP&S memory autoconfig function only works to configure memory within the Zorro II address range; all other memory is added via an "AddMem" type utility at boot time. This auto config function stops working above about 37 Mhz, but if I boot with the autoconfig disabled, I can easily boot at 40mHz and maybe above. I have an L88M mask 40 MHz rated 040 that runs cool in use at these frequencies. Something in the auto config circuitry or bus does not like the higher clock frequencies at boot time. What is the limiting factor here? Thanks for any help you can provide.

Mac

[thebajaguy]

I have this board, and I'll be poking at overclocking and other upgrades in the next few months. One thing that strikes me as confusing is how they fragment the memory space when pushing some of the RAM into AutoConfig space. The memory (2x bank of 4 8-bit SIMMs, either 1MB or 4MB modules) I would push all high and use Z2 space for any 16-bit RAM that might be on other cards. There are tricks I pulled out with ROMTagging tools (AmiNet archives) that can get the RAM auto-recognized after an initial boot/reboot and load libraries and drivers into the high 32-bit memory, getting the best performance, and not needing to AutoConfig 32-bit for a few MB of RAM for early boot.

[wmaciv]

Actually sourced 32 MB of 1K refresh 60ns SIMMS; as expected, they made no difference. Reinstalled the two chip 4K refresh SIMMS. Still waiting for my 70MHz oscillator to see if I can push up from 33 to 35MHz. No joy at 40 MHz with onboard memory. I can boot all the way up to Workbench at 40MHZ no problem, but only if onboard memory is disabled.

[thebajaguy]

I have a few oscillators on the way, 60ns 4MB DRAM modules already in it, and hope to try an 060 adapter soon. I'm using some ROMTag functions to boot, tag the RAM, and reboot, and get many OS structures located in all-upper memory (no memory gaps, and the GVP HC8 can AutoConfig all it's 16-bit RAM for DMA to that, then the driver can CPU copy-up).

Find a memory test program you can run (or try the John Hertel DiagROM if you can burn them) and blast away for a few hours at the <40Mhz speeds to make sure it's truly stable. Test without the AddMem to the OS so you can sweep the whole memory range without stepping on any OS structures.

[idrougge]

I would stay away from overclocking such old cards. It's not the memory or the CPU that is at stake, but the irreplacable reprogrammable logic chips on the card. They may not be made out for higher speeds than the card was originally clocked at, and if one of those is damaged in the process, you have a worthless accelerator board instead of an accelerator that is actually quite fast, if not quite as fast as possible.

[wmaciv]

33MHz is the top speed that still allows the autoconfig function to work in my board. I let the board autoconfig the standard 2 MB into the ZII space, the Thor MuLibs suite to add the rest. Sysinfo showing 24.85 MIPS at 33 MHZ. 1K refresh made zero difference good or bad; went back to the 4K 3 chip low profile SIMMS.

Mac