Some HP-50G Questions

[Claudio L.]

(12-09-2018 11:31 PM)cdmackay Wrote:  

(12-09-2018 06:41 PM)HP67 Wrote:  It seems to me there should be no technical difference of cards based on physical format alone. If you compare specs on both you should find the difference.

yup, sorry, my comment wasn't clear: micro SD and SD should be of equivalent performance, and using an adaptor shouldn't affect that at all.

But I thought I'd noticed that a similarly branded card in micro SD format often had a lower performance rating than the same branded SD. But perhaps I was imagining that.

And counterfeit, as you say…

Here are some quick facts, that may or may not clarify anything at all

* microSD and SD are electrically identical, the adapter is just tracks to put each pin to the right place.
* SD standard has a negotiation in voltage and there's a maximum current too. The faster the card, the more current it draws, and the hotter it gets.
* Faster cards use newer protocols, they aren't any faster if an older host doesn't support the high speed protocol (the 50g being SD 1.1 compatible falls into this category, quite slow).
* microSD cards in older generations were meant for low-powered devices, therefore they were usually slower to limit power consumption. Back then, big SD cards were thought for PCs and camcorders, so performance to record video without skipping was more important.
* The previous statement is 100% untrue nowadays. microSD became the standard for phones, which have a lot of power AND demand a lot of performance. There's virtually no difference between new microSD and big SD cards.
* I had microSD cards that were very fast, but they would shut down due to overheating after less than a minute working at full blast (copying large files). I don't know if to blame the card or the host's socket poor heat dissipation. In other devices the same card would work without any issues.

Regarding boot delays:
* SD cards have a power-up delay that varies from manufacturer to manufacturer. Some cards are ready to receive commands in a few milliseconds, I had others that take 300 ms before they accept the first command. The 50g cuts down power to the card after every single operation, making it unbearably slow on those cards. I had a case of a fast card that tested on a PC was more than twice the speed of another one, but on the 50g it was 4x slower. Investigating the issue I discovered it had 190 ms startup time, ruining the performance on the 50g.
* The above statement is not true when using SDFiler, hpgcc 2.0, hpgcc3 or newRPL, all of which don't power off the card (merely stop its clock, meaning instant wake-up at the expense of a tiny current draw).
* The boot delay on the 50g is due to the ROM computing the free space, for which it needs to read the entire FAT table. The amount of data to read is therefore proportional to the number of clusters, just lower the number of clusters and your 50g boots faster.
* The recommendation to use FAT16 is only because FAT16 is limited to 65536 clusters.
* Since most objects in the 50g are small, using a large cluster size is also a waste, so it's best to use a smaller partition if possible. Now that Windows finally mounts all partitions, I think it's wise to create a first partition with 128 MB (FAT16) and the rest in a FAT32 volume for bigger files.

I hope it saves you some reading from other old threads.