The Performance Edge: PowerLogix And XLR8 Respond To Newer's Claims Regarding G3/G4 Processor Upgrades And Speculative Processing

[Editors note: The publication of Newer's White Papers on the challenges of Speculative Processing and Bus Speed, generated a lot of interest - not the least from Newer's competitors - one of which went so far as to say that the information contained in the Speculative Processing White Paper was an effort by Newer to pollute the G4 upgrade environment until Newer itself was able to get its G4 upgrades out the door (which will be not be until sometime next month, according to Newer). At the time of publication of the two Newer Papers we sent notes off to the other major CPU upgrade manufacturers offering them equal time. The article below contains information from Powerlogix's response and a brief response from XLR8. If you have not done so please first read Newer's White Paper otherwise you might be a little confused]

Speculative Processing Issues with G3/G4 Upgrades - The Powerlogix Perspective

According to Powerlogix you only need to worry about Speculative Processing (SP) issues if you are putting an upgrade in Macintoshes prior to the 8600 and 9600. On these and later machines the motherboard handles SP properly and will adjust correctly for a G3 or G4 processor upgrade. On all other previous machines a SP solution is required otherwise there can be stability problems. These machines include: 7300, 7500, 7600, 8500, 9500, Power Computing PowerCurve, PowerCenter, PowerCenter Pro, PowerTower, PowerTower Pro, PowerWave, PowerBase, UMAX J700, and S900, and Daystar machines.

There are two types of solutions used by CPU upgrade manufacturers on these problem machines. One is a hardware fix (extra chips on the daughter card) that will configure the G3/G4 card on startup automatically. This is the method used by Newer. The problem with this method, according to Powerlogix, is that it adds expense to the manufacturing of the upgrade cards (Powerlogix says $50 or more), and the firmware of these cards is more difficult to update (they say the card must be returned to the factory for adjustment). Even so Powerlogix says it is a good method of overcoming the SP problems with affected machines.

However Powerlogix has chosen the 2nd option - Open Firmware (OF) - a software solution. They call this code 'NVRAM Config' and it is part of of the Powerlogix G3/G4 Cache Profiler software that ships with their cards. The NVRAM Config code is contained in non-volatile RAM, so it will last across reboots and shutdowns. It configures the G3/G4 card very early boot process before such things as PCI cards or SCSI connections are enabled, it is at this point that Speculative Processing is disabled.

In some cases if SP has not been disabled prior to installing a G3/G4 upgrade a Mac will not be able to boot from a SCSI drive. Powerlogix considers this an unlikely possibility but has developed a 30K Boot Diskette that loads, disables SP and then restarts the computer. If you get the blinking question mark you just put the diskette in and after 3 seconds the machine will boot properly from the startup disk. Once you do this you should never have this problem again.

Why did Powerlogix choose the software solution of Open Firmware over a hardware solution? They say it helps to keep the cost of their cards down, allows them to easily update the software adding improvements and bug fixes and performs just as well as the hardware solution.

Read PowerLogix's Complete FAQ On The issue

XLR8's Initial Response

According to XLR8, the "no boot" is strictly not G4 upgrade exclusive and for the most part, it has nothing to do with "G4 Pipelines". The following information was passed on from Gary Daily, Marketing Director at XLR8:

Two issues exist on "Pre-G3 clean" systems:

  1. OS 9 booting on with Speculative Processing enabled.
  2. G4's booting with Speculative Processing enabled.

Issue 1 is strictly OS 9 related, and so far has been limited to using older disk drivers on boot drives. Virtual Firmware does allow the use of older disk drivers on the boot drive. The best solution of course is to update to the newest Disk Drivers on the Mac OS CD. Updating to OS 9 compatible drivers makes all G3 Upgrade Cards 100% bootable with or without firmware or software. Issue 2 is G4 related. Yes, speculative processing must be disabled. The NVRAM (nonvolatile RAM) based, XLR8 Virtual Firmware, and Powerlogix NVRAM Config both work extremely well. Please note as stated below that the NVRAM based software is not as volatile (and much more flexible) than communicated by some companies.

The Mac behaves differently depending on whether it was booted from a cold start (does detailed RAM test as well), or a restart. An Apple Tech Note details this as well.

  • PRAM is ZAPPED by (command-option-p-r) on a restart.
  • NVRAM is ZAPPED by (command-option-p-r) on a cold boot.

Virtual Firmware resides in NVRAM and is not removed except on Zapping of NVRAM from cold boot. All of our troubleshooting documentation suggests booting, performing restart (press control-option-power if the machine is frozen), then Zap PRAM. This maintains Virtual Firmware, which allows users to continue regardless of disk drivers or CPU. We will also include a floppy, or bootable CD for users that have problems, which will automatically disable Speculative Processing, also announced by Sonnet, and Powerlogix.

XLR8 cannot confirm that the Newer cards support older disk drivers on OS 9, we do have about a thousand MACh Speed Control Users with NewerTech cards, and great success though. We stand by the fact that we are compatible with all OS 9 and G4 compatible hardware/software. XLR8 Virtual Firmware is an effective solution for any G3 or G4 upgrades needing to boot their system from a drive using out-dated disk drivers. But again, users should update their drivers as a long term solution.

NVRAM and TechTool

After posting the information above, many of our savvy readers asked us if utilities like the popular TechTool (which includes a PRAM zapping function) would have an impact on the contents of NVRAM. We asked Jeff Baudin, president of MicroMat to address the issue. He assured us that both the freeware and Pro versions of TechTool steer clear of NVRAM to aviod issues like the ones raised above. Future versions of TechTool may include the ability to work with NVRAM but would not allow "blind" zapping of its contents.



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