[Bruce Abbott]

Originally Posted by mc6809e

Page mode certainly did exist at the time. The Acorn Electron (1983) used it to cleverly reduce the number of dram chips from eight to four. It actually had a four bit bus. Page mode was exploited to grab two nibbles to create each needed byte.

Not that clever. It made the Electron's RAM twice as slow as the BBC Micro. That, combined with removing mode 7 (teletext mode) and the sound chip, made the Electron much slower than the previous model as well as making it largely incompatible - not a great idea.

Acorn’s would-be ZX Spectrum killer, the Electron

“The problem was, of course, that the BBC Micro architecture only had 32KB, so if you were using 64Kb DRAM chips, you’d need four of them to give you 32KB and then you’d have to be double-accessing them for every byte you wanted,” Furber says. “That basically drove the Electron architecture: the recognition that for cost reasons we had to go that way. There were inevitable performance compromises as a result of that. We couldn’t do double-access at 4MHz - the memory wasn’t fast enough for that - so we had to accept we were going to have to live with lower total memory bandwidth, which we didn’t like.”

And squeezing all the circuitry required into a single custom chip wasn't wasn't the 'cleverest' idea either...

Acorn marketing manager Tom Hohenberg would many years later place the blame for the slow production ramp on Ferranti - later GEC Plessey - for failing to punch out sufficient working ULAs. Only one in ten worked, he claimed.

Typical how a stupid design from another manufacturer is described as 'clever', while Commodore's (actually Jay Miner's) decisions were called 'regrettable'.

Not sure what you mean by buffering, but Denise and Paula already store multiple bytes before they're needed. Paula stores two byes per channel and Denise stores up to six words for display.

Yes, but the memory cycle timing is the same as the display timing so the buffering is relatively simple. With page mode you have to buffer everything that goes into and out of the RAM, with variable latency. The bandwidth gain isn't great unless you have multiple page mode accesses in sequence, which requires even more buffers and results in even greater latency. Just what you don't need in an already complex design.

Interestingly the Atari ST has a video memory organization that combines both the idea of bitplanes and linear organization with a bitplane words interleaved with each other sequentially in memory.

The Amiga's linear bitmap layout is simpler and more logical.