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| Skipping the Startup Memory Test |
Posted by: jmacz on 2025-09-01 18:55:09
FWIW, this extension seems to work on my PowerBook 3400c.
It passes the test of bit 6 of $2400, sees bit 4 of $2401 is high and then zeros out the NVRAM $1043. Subsequent cold boot has no memory test. |
Posted by: killvore on 2025-09-03 00:41:42
I ran a quick test yesterday which unfortunately did not work 😱
- Power Macintosh 6100
- System 7.6.1
- 256 MB RAM (this is why I want the bypass 😄)
- G3 accelerator
- HPV Card
I did not have so much time to mess around with the components or configuration, will see if it works with a more sensible setup! |
Posted by: jmacz on 2025-09-03 05:56:01
I ran a quick test yesterday which unfortunately did not work 😱
- Power Macintosh 6100
- System 7.6.1
- 256 MB RAM (this is why I want the bypass 😄)
- G3 accelerator
- HPV Card
I did not have so much time to mess around with the components or configuration, will see if it works with a more sensible setup!
@joevt mentioned it would not work on the 6100,7100,8100 due to their HW configuration. @killvore do you know if your machine supports Apples hidden option in OS 8.6? |
Posted by: joevt on 2025-09-03 14:34:14
@joevt mentioned it would not work on the 6100,7100,8100 due to their HW configuration. @killvore do you know if your machine supports Apples hidden option in OS 8.6? The Power Macintosh 6100 emulation at infinitymac.org (uses DingusPPC) doesn't seem to have a memory test option in the Memory control panel of Mac OS 8.0 but does have the option in Mac OS 8.6. I would add some NVRAM logging to DingusPPC to see if it's accessing XPRAM or something. |
Posted by: jmacz on 2025-09-03 19:49:05
The Power Macintosh 6100 emulation at infinitymac.org (uses DingusPPC) doesn't seem to have a memory test option in the Memory control panel of Mac OS 8.0 but does have the option in Mac OS 8.6. I would add some NVRAM logging to DingusPPC to see if it's accessing XPRAM or something.
Cool, thanks! |
Posted by: killvore on 2025-09-04 04:51:33
I tried on my Power Mac 6100 and unfortunately it does not seem to work. I get the "Startup Memory Tests" option in System 8.6 to disable the test in the Memory control panel, but turning the test Off does not have any effect - it still takes forever to do a cold boot. This is true both with and without the G3 accelerator. I also tried with less RAM in case 2x128 was causing weird issues, but no dice. |
Posted by: jmacz on 2025-09-04 20:59:16
I tried on my Power Mac 6100 and unfortunately it does not seem to work. I get the "Startup Memory Tests" option in System 8.6 to disable the test in the Memory control panel, but turning the test Off does not have any effect - it still takes forever to do a cold boot. This is true both with and without the G3 accelerator. I also tried with less RAM in case 2x128 was causing weird issues, but no dice.
I was thinking there could be some additional code paths for different hardware but I didn't notice any while debugging - although I was heavily focused on the particular one that performed the NVRAM writes that @joevt found so I could have missed it. But if you're saying that toggling the hidden option does not work on your 6100, then that suggests the code path might not be there and Apple didn't properly restrict that hidden option from hardware that doesn't support it. But let's wait to see what @joevt finds. |
Posted by: joevt on 2025-09-05 04:43:29
I was thinking there could be some additional code paths for different hardware but I didn't notice any while debugging - although I was heavily focused on the particular one that performed the NVRAM writes that @joevt found so I could have missed it. But if you're saying that toggling the hidden option does not work on your 6100, then that suggests the code path might not be there and Apple didn't properly restrict that hidden option from hardware that doesn't support it. But let's wait to see what @joevt finds. I didn't realize I volunteered.
I am thinking the code path for PDM Macs (6100, etc.) probably involves the stuff I mentioned at:
https://68kmla.org/bb/index.php?threads/skipping-the-startup-memory-test.50699/post-571099
I checked the Memory control panel in DingusPPC. All the options are stored on disk except the RAM Disk size which is stored to offset 0xAF of XPRAM just like for the TNT Macs (7500, etc.) which use NVRAM offset 0x13AF which is offset 0xAF of the XPRAM part in NVRAM.
I didn't try finding the RAM test code during boot. The RAM test on pm6100, if it is happening, seems really fast. I can only add up to 136 or 264 MB of RAM in DingusPPC for the pm6100. The TNT Macs can have up to 1.625 GiB of RAM. |
Posted by: killvore on 2025-09-05 07:02:07
If Apple's own System 8.6 "disable" setting doesn't work on the PDM macs it seems much less likely that there is a software-only solution to bypass the check. Oh well! Still a huge fan of them for some reason I can't really rationalize 😄 |
Posted by: jmacz on 2025-09-05 07:04:29
If Apple's own System 8.6 "disable" setting doesn't work on the PDM macs it seems much less likely that there is a software-only solution to bypass the check. Oh well! Still a huge fan of them for some reason I can't really rationalize 😄
👍 |
Posted by: cgp on 2025-11-21 18:25:23
As a footnote to disabling the boot memory test...
On my beige G3 mini-tower running MacOS9.2, the memory test comes and goes mysteriously. It seems to return spontaneously. It may be that it's enabled by booting into OFW which I frequently do to boot other OSes. Perhaps XPostFacto is involved. But I'm never able to get to this hidden memory control panel option in v8.1.3 using the CMD+OPT keys. With 640MB of RAM, the boot delay is really irritating.
Anyhow, I've just discovered an additional wrinkle. CMD+OPT does't work when the Memory panel is selected in the traditional way from the drop-down from the Apple logo in menu bar! You have to launch the Memory Control Panel from the Control Panel Folder with CMD+OPT. |
Posted by: adespoton on 2025-11-25 10:00:03
Anyhow, I've just discovered an additional wrinkle. CMD+OPT does't work when the Memory panel is selected in the traditional way from the drop-down from the Apple logo in menu bar! You have to launch the Memory Control Panel from the Control Panel Folder with CMD+OPT. Thanks for sharing this! I know I've come across that issue in the past and got really frustrated that cmd-opt didn't work. Now I know why! |
Posted by: feeef on 2025-12-02 06:08:07
I have tested this on my 9500 and it has been working perfectly so far!
Thank you so much @jmacz ! This 9500 has 1.5 GB of RAM and took forever to boot on 7.6.1. It was so long, I ended up using MacOS 9 instead. I am so happy to be back on System 7, which flies on that machine!
@jmacz do you plan to release the source code at some point? I am doing some classic MacOS programming and I would love to see how this extension is made. |
Posted by: jmacz on 2025-12-02 12:10:29
Glad to see it's working for you. I can look into sharing the code when I get a chance. |
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