Thanks for your reply, theos911. The upgrade I have been considering the purchase of is the Sonnet 500MHz G3. I've not considered a G4 as seriously as a G3 upgrade because I am happy to stick with OS 8 and OS 9 on the Wallstreet (no need for OS X on such an old machine). The G4 is more suited for OS X, as discussed here:

http://lowendmac.com/misc/03/1020.html

I too have been searching for the ALLEGRO. In fact, I wrote an email to Wegener Media, who once were distributors of the ALLEGRO. They even have the ALLEGRO web page still up here:

http://www.wegenermedia.com/wllst500.htm

That web page said they stopped selling the ALLEGRO due to "issues on the Motorola chipset." Confused by that, I inquired further with them. Dave (at Wegener Media) wrote me the following reply:

We quite mfr'ing the Wallstreet upgrade mainly due to issues with the Wallstreet's power management.. THe PMUs are wearing out (14yrs is ancient in technological terms), so they aren't reliable. The process is rather time consumptive for a single unit, and as sales are nonexistent, we quit supplying them...
The Allegro was really the best, as it was fast and cool. Unfortunately, we only got the bugs worked out right at the point that the market softened.. So it actually sold less than any of our other upgrade cards..

Click to expand...

Of course, his reply only resulted in more questions in my mind. For truly, the G3's used in these upgrade cards were of a newer, lower power lot than the older version G3s that Apple used. And that is precisely why the ALLEGRO ran cooler than the stock CPU (or so the LEM article says). Therefore, I don't see why the Allegro would put more strain on the PMU than the stock CPU! But I didn't inquire further with Dave about that to know for sure.

Anyway, getting back to the topic of this thread...

I thought that a PC133 SODIMM would do it, but I didn't know about the "2-sided" part. If any of you would happen to have single sided RAM in the 256MB size, and PC133 speed, I may be interested in buying it from you.

Also, this web page seems to indicate that there is no such thing as a single-sided 256MB "low density" SODIMM:

http://www.allmemoryupgrades.com/pc133sodimm.html